Sebastien Meffre
University of Tasmania, Earth Science, Faculty Member
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity,... more
Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.
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Abstract Arsenian pyrite containing above 1 wt. % As plays a crucial role in deposition and deportment of Au and other chalcophile elements. The importance of arsenian pyrite led to theoretical and experimental studies that examined... more
Abstract Arsenian pyrite containing above 1 wt. % As plays a crucial role in deposition and deportment of Au and other chalcophile elements. The importance of arsenian pyrite led to theoretical and experimental studies that examined properties and genesis of the mineral; however, the interpretation of the phase relations between arsenian pyrite and arsenopyrite is conflicting. In this contribution, we present the results of a review of the experimental studies that have investigated the crystallisation of pyrite in As-bearing systems, a summary of As content in pyrite coexisting with arsenopyrite in 37 deposits and the composition of arsenian pyrite in deposits with little or no arsenopyrite. The review demonstrates that the previous experimental studies that attempted to achieve an equilibrium between pyrite and arsenopyrite observed about 1 wt. % As or less in pyrite. The literature survey of the assemblages of pyrite and arsenopyrite shows that pyrite crystallising together with arsenopyrite commonly has a very heterogeneous composition with As content varying from below detection to about 10 wt. % As and no clear discontinuities were observed across this range. In the deposits without arsenopyrite, arsenic content in pyrite can reach 20 wt. % As. We consider three principal scenarios of the relations of arsenian pyrite and arsenopyrite: (A) Pyrite with high As content is stable in equilibrium with arsenopyrite. Low-As pyrite coexisting with arsenopyrite is a product of disequilibrium crystallisation; (B) a scenario of control of As content in pyrite coexisting with arsenopyrite by thermodynamic parameters including temperature, pressure, the activity of components and fluid composition and (C) a scenario where arsenian pyrite is a metastable mineral. The experimental and natural observations are inconsistent with a model of 5–6 wt.% As in pyrite coexisting with arsenopyrite in equilibrium (scenario A). The stability range of the assemblage of pyrite and arsenopyrite constrains the thermodynamic control on the composition of pyrite crystallising in equilibrium with arsenopyrite (scenario B). The scenario of metastable crystallisation of arsenian pyrite (C) proposes formation of the mineral by fast growth from oversaturated fluids with As content controlled by surface adsorption and can explain such features as sector zoning of the mineral and the apparent negative temperature dependence of the solubility. The data phase relations of arsenian pyrite highlight the need for new experimental studies, and suggest that the scenario of disequilibrium phase relations of arsenian pyrite should be considered for interpretation of natural assemblages.
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AIMS: To determine the age and trace element chemistry of zircon crystals from mineral separates.
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Subordinate sapphire accompanies prevalent zircon megacrysts in the Bo Loei basaltic gem field, Ratanakiri Province, Cambodia. These deposits are important for heat-treated gem zircon. Dark blue sapphire, with rare blue-green,... more
Subordinate sapphire accompanies prevalent zircon megacrysts in the Bo Loei basaltic gem field, Ratanakiri Province, Cambodia. These deposits are important for heat-treated gem zircon. Dark blue sapphire, with rare blue-green, orange-brown and yellow stones, up to a few cm in size, include hexagonal-shaped and growth-zoned crystals. Analyses of the sapphires (electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry) showed Fe as the main chromophore (0.6–2.7 wt%), with minor Ti (<0.7 wt%). Sapphire cores show enrichment in Fe relative to rims and some include exotic heavy elements (Nb up to 56, Ta up to 144, Sn up to 5 ppm). The sapphires show high Ga values (271–724 ppm) and Ga/Mg ratios (4.8–77.0) suggesting magmatic associations. Two sapphires with syngenetic inclusions (zircon, Nb-rich rutile) gave U–Pb (Th-disequilibrium corrected) ages at ca 0.93 ± 0.1 Ma. The Bo Loei sapphires show higher Fe and Ga than other magmatic sapphire suites elsewhere in...
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The overarching aims of this study are: Determination of gold-containing mineral phases, as well as gold and other trace element contents, in pyrite and arsenopyrite by combining results from Mineral Liberation Analysis (MLA) and laser... more
The overarching aims of this study are: Determination of gold-containing mineral phases, as well as gold and other trace element contents, in pyrite and arsenopyrite by combining results from Mineral Liberation Analysis (MLA) and laser ablation mass spectrometry (LA-ICPMS) on 10 rock core samples.
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Aim: To determine the age of some of the epidote analysed previously for their trace elements contents in CODES-LA-ICPMS facilities during the last 5 years (2013-2018).
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809 New insights into the 3.4 Ga sulfur and iron cycle from the ICDP Buck Reef Chert drill core B. EICKMANN1, A. HOFMANN1, A. AGANGI2, M. WILLE3, S. MEFFRE4, B. WING5 AND R. SCHOENBERG3 1Department of Geology, University of Johannesburg,... more
809 New insights into the 3.4 Ga sulfur and iron cycle from the ICDP Buck Reef Chert drill core B. EICKMANN1, A. HOFMANN1, A. AGANGI2, M. WILLE3, S. MEFFRE4, B. WING5 AND R. SCHOENBERG3 1Department of Geology, University of Johannesburg, South Africa 2Department of Applied Geology, Curtin University, Australia 3Department of Geosciences, Tübingen University, Germany 4CODES and School of Earth Sciences, University of Tasmania, Australia 5Department of Earth and Planetary Sciences and GEOTOP, McGill University, Canada
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12 Magmatic differentiation and/or assimilation and related segregation of immiscible sulfide 13 liquid are generally believed to be critical processes in the formation of the majority of 14 orthomagmatic Ni sulfide deposits. In recent... more
12 Magmatic differentiation and/or assimilation and related segregation of immiscible sulfide 13 liquid are generally believed to be critical processes in the formation of the majority of 14 orthomagmatic Ni sulfide deposits. In recent years, a new class of Ni sulfide deposits formed by 15 metasomatic and/or hydrothermal modification of peridotites has been recognized. The 16 serpentinite-hosted Avebury Ni sulfide deposit (Tasmania, Australia), the largest known non17 magmatic deposit, provides an unprecedented opportunity to understand sources of metals and 18 fluids responsible for this style of economic mineralization. Our study shows that 19 serpentinization of the Ni-bearing olivine in the Cambrian peridotites of the McIvor Hill 20 complex was followed by metasomatic transformation assisted by heat and fluids supplied by the 21 nearby Late Devonian granite intrusion. The role of the above in the formation of an economic 22 concentration of Ni sulfides is supported by 1) abundan...
ABSTRACT Malaysia is endowed with a number of major sediment-hosted, orogenic gold deposits that lie parallel to but east of the Bentong-Raub Suture Zone, which runs approximately N-S in central Malaysia. The Selinsing gold deposit is one... more
ABSTRACT Malaysia is endowed with a number of major sediment-hosted, orogenic gold deposits that lie parallel to but east of the Bentong-Raub Suture Zone, which runs approximately N-S in central Malaysia. The Selinsing gold deposit is one of the major economic deposits in central Malaysia and is hosted by (meta)-sedimentary units. The deposit is affected by later deformation and metamorphism during the Triassic due to the collision of the Sibumasu Terrane with the Sukhothai Arc. Laser ablation ICP-MS U-Pb zircon dating of the host rocks indicates a Carboniferous (ca. 331-300 Ma) maximum depositional age. Ore minerals include pyrite, arsenopyrite, galena, sphalerite, chalcopyrite, pyrrhotite and gold. Detailed textural and geochemical studies revealed five distinctive pyrite types, sub-rounded framboidal pyrite (Pyrite 1), rounded recrystallized pyrite (Pyrite 2), anhedral inclusion-rich pyrite (Pyrite 3), anhedral to subhedral clean pyrite (Pyrite 4) and coarse euhedral clean pyrite (Pyrite 5). Laser ablation ICP-MS trace element analysis of the framboidal pyrite indicates enrichment in V, As, Mo, Ni, Se, Te, Ag, and Zn relative to the other pyrite types. Pyrite sulfur isotope composition (1.2 – 9.2 ‰) suggests a likely mixture of magmatic and local sedimentary source for the sulfur. Pyrite Pb isotope results (Pb206/Pb204: 18.94-19.10; Pb207/Pb204: 15.72-15.73) suggest a high-U source rock for the lead. Fluid inclusions are CO2-rich (95-100 mole %) and yielded homogenization temperatures from 194 to 348 °C and salinities between 1.23 and 9.98 wt % NaCl equiv. suggesting involvement of metamorphic fluids during ore formation. Based on these results, we suggest a two-stage model for the formation of the gold deposit at Selinsing. Stage 1 consists of early enrichment of the elements Au, V, As, Mo, Se, Te, Ni, Ag, and Zn in framboidal pyrite in the sediments, whereas Stage 2 is characterized by multiple post-diagenetic deformation and metamorphic processes, favouring the development of fluid pathways and Au remobilization into later pyrites. Regionally, the Selinsing gold deposit shares geological similarities (in term of host rocks, ore mineralogy and geochemistry) with many other sediment-hosted, orogenic gold deposits in mainland SE Asia such as the Sepon gold deposit (Laos), Langu gold deposit (Thailand), Modi Taung and Meyon gold deposits (Myanmar), and Phuoc Son gold deposit (central Vietnam). We suggest that our two-stage model may have important implications to mineral exploration for future research on sediment-hosted/orogenic gold deposits in SE Asia.
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Mining of larger, lower grade deposits across several commodities (e.g., Cu, Au, Pb, Zn) in recent decades has led to an increase in the quantities of mine wastes being produced. These materials may contain reactive minerals, including... more
Mining of larger, lower grade deposits across several commodities (e.g., Cu, Au, Pb, Zn) in recent decades has led to an increase in the quantities of mine wastes being produced. These materials may contain reactive minerals, including sulfides, and therefore require appropriate management to mitigate against environmental impacts including the formation of acid and metalliferous drainage (AMD). Common AMD remediation strategies involve the application of introducing covers and using chemical or biological techniques to stabilise these wastes, though the long-term success of these strategies is not guaranteed as examples across Australia (e.g., Ranger, Mary Kathleen) have demonstrated. Instead, determining if new economy metals or additional base or precious metals are contained in sulfidic mine waste at economic concentrations presents an opportunity to both reduce AMD risk and recover additional commodities. In this study, geometallurgical characterisation of mine tailings at two ...
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Research Interests: Geology, Geochemistry, Geophysics, Geochronology, Gondwana, and 5 moreOrdovician, Paleozoic, Zircon, Plutonism, and back arc basin
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... arc of the Cordón de Lila (northern Chile) ... A new study of the Cordón de Lila Ordovician volcano-sedimentary successions in northern Chile reveals for the first time an arc assemblage deposited on thin crust within a continental... more
... arc of the Cordón de Lila (northern Chile) ... A new study of the Cordón de Lila Ordovician volcano-sedimentary successions in northern Chile reveals for the first time an arc assemblage deposited on thin crust within a continental arc system, having regional implica-tions. ...
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ABSTRACT Coronation Hill is a U + Au + platinum group elements deposit in the South Alligator Valley (SAV) field in northern Australia, south of the better known unconformity-style U East Alligator Rivers (EAR) field. The SAV field... more
ABSTRACT Coronation Hill is a U + Au + platinum group elements deposit in the South Alligator Valley (SAV) field in northern Australia, south of the better known unconformity-style U East Alligator Rivers (EAR) field. The SAV field differs from the EAR by having a more complex basin-basement architecture. A volcanically active fault trough (Jawoyn Sub-basin) developed on older basement and then was disrupted by renewed faulting, before being buried beneath regional McArthur Basin sandstones that are also the main hanging wall to the EAR deposits. Primary mineralisation at Coronation Hill formed at 1607 ± 26 Ma (rather than 600-900 Ma as previously thought), and so it is likely that the SAV was part of a single west McArthur Basin dilational event. Most ore is hosted in sub-vertical faults and breccias in the competent volcanic cover sequence. This favoured fluid mixing, acid buffering (forming illite) and oxidation of Fe2+ and reduced C-rich assemblages as important uranium depositional mechanisms. However, reduction of U in fractured older pyrite (Pb model age of 1833 ± 67 Ma) is an important trap in diorite. Some primary ore was remobilised at 675 ± 21 Ma to form coarse uraninite + Ni-Co pyrite networks containing radiogenic Pb. Coronation Hill is polymetallic, and in this respect resembles the `egress&amp;#39;-style U deposits in the Athabascan Basin (Canada). However, these are all cover-hosted. A hypothesis for further testing is that Coronation Hill is also egress-style, with ores formed by fluids rising through basement-hosted fault networks (U reduction by diorite pyrite and carbonaceous shale), and into veins and breccias in the overlying Jawoyn Sub-basin volcano-sedimentary succession.
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... Fig. 1. Simplified regional geological map of Bafq Mineral Province (modified after Haghipour, 1977, Soheili and Mahdavi, 1991, Majidi and Babakhani, 1995, [Ramezani and Tucker, 2003], Amini, 2004, Ghaemi and Saidi, 2006 and [Jami et... more
... Fig. 1. Simplified regional geological map of Bafq Mineral Province (modified after Haghipour, 1977, Soheili and Mahdavi, 1991, Majidi and Babakhani, 1995, [Ramezani and Tucker, 2003], Amini, 2004, Ghaemi and Saidi, 2006 and [Jami et al., 2007]). View thumbnail images. ...
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HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad,... more
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Earliest Eocene (53 Ma) convergence in the Southwest Pacific; evidence from pre-obduction dikes in the ophiolite of New Caledonia.
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Tectonic unroofing of the Tertiary high pressure metamorphic core complex of northern New Caledonia, Pacific. A kinematic analysis) (French with abridged English Denudation tectonique du complexe a noyau metamorphique de haute pression d'age tertiaire (nord de la Nouvelle-Caledonie, Pacifique, Francmore
A kinematic analysis allows a new interpretation of the metamorphic zoning and tectonic structure of the Upper Eocene high-pressure metamorphic core complex of northern New Caledonia to be proposed. A three-step evolution is proposed: 1)... more
A kinematic analysis allows a new interpretation of the metamorphic zoning and tectonic structure of the Upper Eocene high-pressure metamorphic core complex of northern New Caledonia to be proposed. A three-step evolution is proposed: 1) subduction of previously thinned continental crust elements; 2) subduction blocking due to the crustal thickening; 3) crustal thinning and extensional detachment during the diapir-like uplift and unroofing of the eclogitic core. Such a model accounts for the thermobarometric and radiochronologic data, and also for the weakness of substratum deformation and absence of metamorphic sole during the emplacement of the ophiolitic nappe. -English summary
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This record presents trace-element and chronologic data collected from zircon and baddeleyite at the Australian Research Council Centre of Excellence in Ore Deposits (CODES) at the University of Tasmania in June 2015. The work was carried... more
This record presents trace-element and chronologic data collected from zircon and baddeleyite at the Australian Research Council Centre of Excellence in Ore Deposits (CODES) at the University of Tasmania in June 2015. The work was carried out in support of the Northern Territory Geological Survey (NTGS) regional geoscientific investigations and value adds to co- funded drill core acquired during Geophysics and Drilling Collaborations program, Round 2. Isotope data and interpretations for zircon and baddeleyite from samples of Mount Peake Gabbro, Arunta Region in the Northern Territory are presented herein. The Mount Peake Gabbro is a magnetite-rich gabbro and is host to the Mount Peake Fe-V-Ti deposit. The age of the country rocks intruded by the gabbro is unknown but is interpreted to be Palaeoproterozoic thus constraining the maximum crystallisation age of the Mount Peake Gabbro. The samples were collected with the aim of constraining the timing of this episode of mafic magmatism ...
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Dispersed gem corundum is mined from placers, commonly from basalt fields, as occurs along eastern Australian and Asian continental margins. New laser ablation inductively coupled plasma mass spectrometry analysis (LA-ICP-MS) of... more
Dispersed gem corundum is mined from placers, commonly from basalt fields, as occurs along eastern Australian and Asian continental margins. New laser ablation inductively coupled plasma mass spectrometry analysis (LA-ICP-MS) of Australian corundum allows genetic distinctions among these suites and gives clues to their primary lithospheric sources prior to basaltic delivery. Bimodal corundum suites at Barrington Tops, Cudgegong-Gulgong-Macquarie River and Yarrowitch, New South Wales (NSW), include lower Ga, higher Mg ‘metamorphic’ and higher Ga, lower Mg ‘magmatic’ groups. The Barrington Tops ‘metamorphic’ corundum is more Fe-rich (av 4500 - 7100 ppm) than Cudgegong- Macquarie River equivalents (av Fe 1800 - 2100 ppm). Yarrowitch corundum is relatively low in Fe, Ti and Cr. Along with other eastern Australian data (north-east Tasmania; New England, NSW) and from gem fields elsewhere, the combined trace element and O isotope data, reveal considerable geographic and genetic variations...
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Pyrite and pyrrhotite are commonly associated minerals in many economic deposits and black shales across the world. The metamorphic reduction of diagentic pyrite into pyrrhotite is known to result in the release of sulfur, thereby... more
Pyrite and pyrrhotite are commonly associated minerals in many economic deposits and black shales across the world. The metamorphic reduction of diagentic pyrite into pyrrhotite is known to result in the release of sulfur, thereby enabling further formation of other metal- sulfide clusters. We discuss here the various geochemical and and physiochemical transitions that result during this reduction. We observe that diagenetic pyrite has the ability to encorporate a range of trace elements (T.E.), likely sourced from seawater and intertitial pore waters [1] [2], of which, a large majority (e.g. Zn, Cu, Ag, Au and Pb) are liberated during the conversion. We also present preliminary work on a magnetic study of these two sulfide phases where we observe that pyrite has a distinct magnetic characteristic, akin to that of pyrrhotite, at temperatures far below the published phase transition [3] [4]. We present a series of case studies utilising, real-world examples of this transition and com...
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AIMS: To determine the age and trace element chemistry of zircon crystals from the mineral separates of five samples.
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Sulfide and oxide trace element geochemical analyses have been conducted on more than 290 drill core samples from 39 drillholes across South Australia, as part of a collaborative project between Centre for Ore Deposit and Exploration... more
Sulfide and oxide trace element geochemical analyses have been conducted on more than 290 drill core samples from 39 drillholes across South Australia, as part of a collaborative project between Centre for Ore Deposit and Exploration Science (CODES), University of Tasmania, and the Geological Survey of South Australia. The project aim was to analyse the mineral chemistry of pyrite, hematite and magnetite across a range of deposit styles in SA, and determine whether the technique could be used to provide insights into, and vector within, the various mineral systems. Pyrite analyses showed discernible trends for individual mineralisation types. For example, pyrite which forms in an IOCG-type environment typically contains Co>>Ni, with varying amounts of As, Te, Ag, and Au. Cobalt, Ni, and As are exclusively lattice-bound, whereas Te, Ag, and Au are commonly hosted as inclusions of Au-Ag telluride phases or electrum (AuAg alloy). Hematite and magnetite analyses from different mag...
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Analytical Aims: To determine the trace element contents of pyrite and pyrrhotite in samples from the vicinity of the Cannington Mine and compare this to pyrite and pyrrhotite trace element data previously acquired from the deposit.
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AIMS: To determine the age and trace element chemistry of zircon crystals from five mineral separates.
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The initial stage of Rodinia supercontinent break-up occurred at about 750 Ma. It preceded formation of the Irkutsk and Franklin large igneous provinces (LIPs) at 712 ± 2 to 739 ± 8 Ma. These LIPs were emplaced within the formerly... more
The initial stage of Rodinia supercontinent break-up occurred at about 750 Ma. It preceded formation of the Irkutsk and Franklin large igneous provinces (LIPs) at 712 ± 2 to 739 ± 8 Ma. These LIPs were emplaced within the formerly connected Laurentian and Siberian cratons. The Kingash massif is located in the Precambrian Kan terrane in direct contact with the Siberian Craton at its southwestern boundary. It has been linked to an important suite of mafic–ultramafic intrusions that border the southern margin of the Siberian craton, and that have been inferred to belong to the Irkutsk LIP. The massif is also significant, because it hosts platinum group element (PGE)–Cu–Ni-rich mineralization and is the only large deposit in the region. However, despite numerous dating attempts, the age of the massif had not been resolved. A significant difficulty is post-magmatic recrystallization at amphibolite facies that affected the rocks of the massif. In this study we used U–Pb dating of zircon, ...
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The post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe... more
The post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Népoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recove...
Research Interests: Geology, Paleontology, Peridotite, SW Pacific, Memoirs, and 4 moreNeogene, Ophiolite, Sedimentary Rock, and Obduction
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Aluminum-phosphate-sulfate (APS) minerals of the alunite supergroup are minor components of uranium-bearing copper ores from the Olympic Dam deposit, South Australia. They typically represent a family of paragenetically late replacement... more
Aluminum-phosphate-sulfate (APS) minerals of the alunite supergroup are minor components of uranium-bearing copper ores from the Olympic Dam deposit, South Australia. They typically represent a family of paragenetically late replacement phases after pre-existing REE-bearing phosphates (fluorapatite, monazite, and xenotime). Characterization with respect to textures and composition allows two groups to be distinguished: Ca-Sr-dominant APS minerals that fall within the woodhouseite and svanbergite compositional fields; and a second REE- and phosphate-dominant group closer to florencite in composition. All phases nevertheless display extensive solid solution among end-members in the broader APS clan and show extensive compositional zoning at the grain-scale. Samples representative of the deposit (flotation concentrate and tailings), as well as those that have been chemically altered during the processing cycle (acid leached concentrate), were studied for comparison. NanoSIMS isotope ma...
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Greece contains several gem corundum deposits set within diverse geological settings, mostly within the Rhodope (Xanthi and Drama areas) and Attico-Cycladic (Naxos and Ikaria islands) tectono-metamorphic units. In the Xanthi area, the... more
Greece contains several gem corundum deposits set within diverse geological settings, mostly within the Rhodope (Xanthi and Drama areas) and Attico-Cycladic (Naxos and Ikaria islands) tectono-metamorphic units. In the Xanthi area, the sapphire (pink, blue to purple) deposits are stratiform, occurring within marble layers alternating with amphibolites. Deep red rubies in the Paranesti-Drama area are restricted to boudinaged lenses of Al-rich metapyroxenites alternating with amphibolites and gneisses. Both occurrences are oriented parallel to the ultra-high pressure/high pressure (UHP/HP) Nestos suture zone. On central Naxos Island, colored sapphires are associated with desilicated granite pegmatites intruding ultramafic lithologies (plumasites), occurring either within the pegmatites themselves or associated metasomatic reaction zones. In contrast, on southern Naxos and Ikaria Islands, blue sapphires occur in extensional fissures within Mesozoic metabauxites hosted in marbles. Minera...
Research Interests: Geology, Geochemistry, Trace element Geochemistry, Minerals, Ruby, and 6 moreGreece, Sapphire, Zircon, Origin, Corundum, and Phlogopite
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The accuracy of zircon U–Pb dating by LA-ICPMS is limited by matrix effects related to differences in U–Pb fractionation between an unknown and the calibration standard.
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Abstract The Karoo-Ferrar igneous province is one of the largest igneous provinces on Earth. It extends from South Africa, along the Trans-Antarctic Mountains to Tasmania and South Australia. Reconstruction of the continents back to the... more
Abstract The Karoo-Ferrar igneous province is one of the largest igneous provinces on Earth. It extends from South Africa, along the Trans-Antarctic Mountains to Tasmania and South Australia. Reconstruction of the continents back to the Gondwana configuration in the Early Jurassic reveals a total length of the Karoo-Ferrar province of > 5000 km. New isotope dilution thermal ionization mass spectrometry (ID-TIMS) single grain U-Pb ages for zircon and baddeleyite from Tasmanian dolerites combined with ID-TIMS literature single grain U-Pb ages from the Ferrar and Karoo suites are consistent with the major pulse of synchronous magmatism throughout the province lasting about 1 Ma or less for the major pulse of magmatism at the time of the Toarcian mass extinction event. We argue that the mechanism of synchronization of magmatism over such a short period of time along such a long distance is the major question which has to be answered in search of the correct model for the origin of the Karoo-Ferrar large igneous province. It cannot be reconciled with the lower mantle plume head model with the plume impingement beneath the Karoo. Plume material could not spread beneath the lithosphere at a rate of ~ 5–10 m/yr (5000 km per 0.5–1 Myr), at least based on the current knowledge of the mantle physical properties. It seems unlikely that the entire Karoo-Ferrar large igneous province formed due to long distance magma migration through dykes from the same mantle plume irrespective on the proposed plume centre location. In such case, magma would have had to cross the boundaries (and thus weakness zones) between three future continents. In the framework of the dyke propagation model we would expect dykes to follow these weakness zones, not cross them. In addition to this, the Karoo and Ferrar contain geochemically different igneous rocks, which were not formed from the same magma source, preventing interpretations based on one single plume. Both the Karoo and Ferrar contain low-Ti tholeiites, which are similar by their trace element patterns to modern arc analogues – the Central Andes and Kamchatka, respectively. Thus, our preferred model for the origin of the Karoo-Ferrar large igneous province is associated with subduction of the Phoenix plate beneath the southern Gondwana. Probably, deep slab dehydration at the depth of the mantle transition zone modulated surface volcanism or the Toarcian tectonic event triggered voluminous but short-term melting of mantle, which was metasomatized by subduction-derived fluids.
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This paper presents results of a laser ablation – inductively coupled plasma – quadrapole mass spectrometer (LA–ICP–QMS) U–Pb dating study of small in situ zircon grains from samples collected in the vicinity of the Greens Creek massive... more
This paper presents results of a laser ablation – inductively coupled plasma – quadrapole mass spectrometer (LA–ICP–QMS) U–Pb dating study of small in situ zircon grains from samples collected in the vicinity of the Greens Creek massive sulphide deposit, on northern Admiralty Island, southeast Alaska. The Greens Creek mine is a volcanogenic massive sulphide deposit in the central portion of the Alexander Triassic metallogenic belt (ATMB) and is one of the top global silver producers despite having a dominantly mafic metavolcanic stratigraphic footwall. The stratigraphic footwall is a Mississippian mafic metavolcanic sequence with a protolith age of approximately 340–330 Ma. The first U–Pb zircon constrained chronostratigraphy for the area places the deposit near, or at, the base of the host Late Triassic stratigraphy just above an approximately 100 million year old unconformity and probably 10–15 million years older than mineralization at the Palmer and Windy Craggy deposits in the ...
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Research Interests: Earth Sciences, Geology, Tectonics, Seismology, Subduction, and 3 moreCOLLISION, New Hebrides, and Ridge
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A new model for the formation of some orogenic gold deposits suggest that diagenetic pyrite within carbonaceous shale may be the source of gold for the deposit. Gold and trace metals enriched in early diagenetic pyrite are remobilised by... more
A new model for the formation of some orogenic gold deposits suggest that diagenetic pyrite within carbonaceous shale may be the source of gold for the deposit. Gold and trace metals enriched in early diagenetic pyrite are remobilised by metamorphic or hydrothermal fluids and re-deposited in favourable trap sites. However, current research has focussed on Proterozoic aged deposits, such as Sukoi Log, Russia. In our study, we examine whether the same processes are responsible for the formation of Archean aged orogenic gold deposits in the St. Ives district, Western Australia. The St. Ives district has undergone five different deformation events, three of which are related to gold mineralization. The first gold mineralization event is associated with the third deformation event and oxidizing fluids generated extensive magnetite alteration along the major structures in the district. These magnetite zones are important because they serve as trap sites for subsequent mineralization event...
Research Interests: Geology, Geochemistry, Diagenesis, Oil Shale, Proterozoic, and 4 moreArchean, Pyrite, Metallogeny, and Trace element
Processes in which trace metals are incorporated into pyrite that forms under euxinic conditions in organic rich sediments are important for several reasons. Recent models proposed by Large et al. (2011) suggest that pyrite is an... more
Processes in which trace metals are incorporated into pyrite that forms under euxinic conditions in organic rich sediments are important for several reasons. Recent models proposed by Large et al. (2011) suggest that pyrite is an important source of gold in orogenic and Carlin style gold deposits. It is also possible that pyrite sequesters many potentially toxic trace metals and metalloids. Finally, as pyrite is a sink for trace metals it can be used as a tool for determining paleocean chemistry. Traditional methods to determine trace metal content of syngenetic to diagenetic pyrite involve using partial extractions to release the trace metals contained within the sulphide phase. While this is a useful technique when pyrite is the only sulphide phase in the sample and there is only one phase of pyrite deposited, there are significant selectivity issues when these criteria are not met. In contaminated sites there are often several different sulphides and other phases that can dissolv...
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The southern Chindwin Basin is characterized by clastic sequences of Pondaung Formation (Late Middle Eocene) and Yaw Formation (Late Eocene). The Pondaung Formation was deposited in a fluvial system of braided to meandering river... more
The southern Chindwin Basin is characterized by clastic sequences of Pondaung Formation (Late Middle Eocene) and Yaw Formation (Late Eocene). The Pondaung Formation was deposited in a fluvial system of braided to meandering river deposits. The most widely distributed and dominated units of the Pondaung Formation are thick bedded, coarse grained volcaniclastic sandstones in the lower part and thick variegated clays in the upper part. The Yaw Formation was deposited in a deltaic system dominated by a thick sequence of shale with sandstone intercalations. LA ICP-MS U-Pb zircon geochronology of the detrital zircon grains from the volcaniclastic sandstone units of the Pondaung Formation yielded an Early Middle Eocene age (51.6 and 43.3 Ma or average age around 47.2 Ma). Petrographic and XRF-immobile trace elements studies of the volcaniclastic components of the Pondaung sandstones indicate that they are plagioclase feldspar-phyric volcanic lithic fragments with andesite and minor rhyodac...
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The G-Plate Program is a powerful freeware that is capable for both the visualization and the manipulation of plate tectonic reconstructions (see http://www.gplates.org/). Developed by the EarthByte Project in the School of Geosciences at... more
The G-Plate Program is a powerful freeware that is capable for both the visualization and the manipulation of plate tectonic reconstructions (see http://www.gplates.org/). Developed by the EarthByte Project in the School of Geosciences at the University of Sydney, the program is newly adopted for our SE Asia tectonic reconstruction. Our SE Asia tectonic reconstruction is built on the global G-Plate tectonic model constructed by Seton et al. (2012) and Wright et al. (2012). We have substantially modified the SE Asia part of their works, based on our new founding and recent important published literature. For instance, the Paleozoic SE Asia tectonic history has been referenced from Sone and Metcalfe (2008) and Metcalfe (2006; 2009; 2012; 2013), whereas the Mesozoic and Cenozoic SE Asia tectonic history have been referenced from e.g., Aitchison et al. (2011); Hall (2002, 2009, 2012), Searle et al. (2012; 2010) and Searle and Morley (2011). Paleolatitudes of the various East Asia tecton...
The Jinshajiang-Ailaoshan-Song Ma Fold Belts preserve the remnants of an important Eastern Paleotethys branch that once separated the South China and Indochina blocks. The fold belts are also of immense economic significance for hosting... more
The Jinshajiang-Ailaoshan-Song Ma Fold Belts preserve the remnants of an important Eastern Paleotethys branch that once separated the South China and Indochina blocks. The fold belts are also of immense economic significance for hosting various mineral deposits, notably porphyry Cu deposits (e.g., Khin Zaw et al., 2007), VHMS polymetallic and orogenic/sediment-hosted Au deposits (e.g., Hou et al., 2007). Regional correlation for these fold belts is thus important not only to understand the tectonic evolution of the mainland SE Asia, but also has substantial implication for regional mineral exploration. Compiling our new and existing geochronological and geochemical data (e.g., Jian et al., 2009; Zi et al., 2012), we suggest that these three fold belts have highly similar tectonic history, with common features include: 1. Siluro-Devonian continental rift magmatism; 2. Devono-Carboniferous volcanic passive margin-break up magmatism; 3. Carboniferous pelagic sedimentation; 4. Late Carb...
Kimberlites and orangeites (previously named Group-II kimberlites) are small-volume igneous rocks occurring in diatremes, sills and dykes. They are the main hosts for diamonds and are of scientific importance because they contain... more
Kimberlites and orangeites (previously named Group-II kimberlites) are small-volume igneous rocks occurring in diatremes, sills and dykes. They are the main hosts for diamonds and are of scientific importance because they contain fragments of entrained mantle and crustal rocks, thus providing key information about the subcontinental lithosphere. Orangeites are ultrapotassic, H2O and CO2-rich rocks hosting minerals such as phlogopite, olivine, calcite and apatite. The major, trace element and isotopic compositions of orangeites resemble those of intensely metasomatized mantle of the type represented by MARID (mica-amphibole-rutile-ilmenite-diopside) xenoliths. Here we report new data for two MARID xenoliths from the Bultfontein kimberlite (Kimberley, South Africa) and we show that MARID-veined mantle has mineralogical (carbonate-apatite) and geochemical (Sr-Nd-Hf-O isotopes) characteristics compatible with orangeite melt generation from a MARID-rich source. This interpretation is sup...
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Gold mineralization at the Tropicana mine occurs within the Plumridge terrane along the eastern margin of the Archean Yilgarn craton in the Albany-Fraser orogen, Western Australia. Mineralization is hosted in a favorable syenitic... more
Gold mineralization at the Tropicana mine occurs within the Plumridge terrane along the eastern margin of the Archean Yilgarn craton in the Albany-Fraser orogen, Western Australia. Mineralization is hosted in a favorable syenitic lithofacies of the Tropicana Gneiss with a minimum igneous age of 2638 ± 4 Ma (2 σ ) and which was metamorphosed to mid-amphibolite to lower granulite facies in the period ca. 2638 to 2520 Ma. The Tropicana Gneiss was exhumed to crustal levels equivalent to greenschist-facies conditions by the time of economic gold mineralization. The major gold-bearing pyrite-biotite-sericite mineralization formed in association with shear zones during northeast-southwest compression (D3) that postdated W- to NW-verging thrusting (D2). The late fluid-induced event (Tropicana event; Doyle et al., 2013; Blenkinsop and Doyle, 2014) produced a mineral assemblage indicative of greenschist-facies conditions. The paucity of water in granulite-facies gneisses under retrograde conditions suggests that fluids were introduced from an external source for both mineralization and the younger metamorphic event. This occurred at ca. 2520 Ma as determined from biotite (ca. 2515 Ma, 40Ar/39Ar age), pyrite (ca. 2505 Ma, Re-Os, Pb/Pb ages), and tungsten-rich rutile (2521 ± 5 Ma, U-Pb age): the latter is considered to provide the best direct measurement age of gold mineralization. The Tropicana Gneiss was derived from the upthrusted easternmost margin of the underlying Yilgan craton, or represents a relatively small (160 km long × 50 km wide) remnant crustal block accreted to the Yilgarn craton sometime between ca. 2.6 and 2.5 Ga. The timing of the Tropicana mineralization is distinctly younger than greenstone-associated gold deposits elsewhere in the Yilgarn craton. As in the Dharwar craton, India, and the Limpopo belt, Zimbabwe, economic gold mineralization at Tropicana postdates the major peak of Late Archean world-class gold mineralization (ca. 2.65 Ga) by more than 100 m.y. The Tropicana Gneiss was relatively unaffected during the younger Albany-Fraser orogeny, with only minor remobilization of gold. Deformation may have been localized at the margins of the domain, between constituent ridged structural blocks, and/or within discrete high-strain shears.
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Research Interests: Geology, Minerals, Sapphire, Trace Elements, Trace element, and 3 moreSapphires, Corundum, and rubies
With ever-increasing emphasis placed on environmental change, shelf areas and enclosed basins are the most prone to the impacts of climatic variations. Effects such as oxygen depletion, water column stratification and temperature... more
With ever-increasing emphasis placed on environmental change, shelf areas and enclosed basins are the most prone to the impacts of climatic variations. Effects such as oxygen depletion, water column stratification and temperature variations are focused in such settings, and can be recorded by the behaviour of trace elements in this changing depositional environment. The Baltic Sea Basin is in a unique position to have experienced and recorded a multitude of environmental changes on a large scale. Over 1.6km of sediment was drilled and logged as part of the IODP Expedition 347. Presented here is a summary of the sedimentology and preliminary geochemistry from sites across the Baltic Sea, one of the world's largest modern intercontinental basins. This Mission Specific Platform focussed on the extreme climatic variations experienced by the Baltic Sea Basin over the Pleistocene and Holocene, exploring not only the fluxes between freshwater and marine conditions during the past glaci...
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ABSTRACT Tasmania forms an enigmatic province within the Neoproterozoic history of Australia. While now part of Australia, it was closer to East Antarctica in the Cambrian. It also lies at the boundary between Australia and North America... more
ABSTRACT Tasmania forms an enigmatic province within the Neoproterozoic history of Australia. While now part of Australia, it was closer to East Antarctica in the Cambrian. It also lies at the boundary between Australia and North America in most Rodinia reconstructions. The Tasmanian Proterozoic stratigraphy has some common features with South Australia but there are major differences. New chemical U–Th–Pb monazite dating demonstrates that Tasmania was metamorphosed at 1290Ma and again at 920Ma, and intruded by granitoids at 1050Ma. These results and a compilation of other data relevant to the Proterozoic evolution of Tasmania are used to test several aspects of Rodinia reconstructions. The Mesoproterozoic tectonic history of Tasmania is similar to the Musgrave Block in central Australia. However, the best correlation of Proterozoic history for Tasmania is with the Transantarctic Mountains. We conclude that the Western Tasmanian Terrane rifted from the East Antarctic margin at 580Ma and was trapped outboard of the Cambrian Ross-Delamerian Orogen. The Victoria Land-Transantarctic Mountains-Western Tasmania block has many similarities to southwest Laurentia and provides additional support for the AUSWUS reconstruction of Rodinia.
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... Geochronology and geochemistry of the Dunedin Volcanic Group, eastern Otago, New Zealand. New Zealand Journal of Geology and Geophysics 51: 196-218. ... Geology, geochronology andgeochemistry of a basanitic volcano, White Island, Ross... more
... Geochronology and geochemistry of the Dunedin Volcanic Group, eastern Otago, New Zealand. New Zealand Journal of Geology and Geophysics 51: 196-218. ... Geology, geochronology andgeochemistry of a basanitic volcano, White Island, Ross Sea, Antarctica. ...
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ABSTRACT The Bavanat Cu–Zn–Ag Besshi-type volcanogenic massive sulfide (VMS) deposit occurs within the Surian volcano-sedimentary complex in the Sanandaj–Sirjan zone (SSZ) of southern Iran. The Surian complex is comprised of pelite,... more
ABSTRACT The Bavanat Cu–Zn–Ag Besshi-type volcanogenic massive sulfide (VMS) deposit occurs within the Surian volcano-sedimentary complex in the Sanandaj–Sirjan zone (SSZ) of southern Iran. The Surian complex is comprised of pelite, sandstone, calcareous shale, basalt, gabbro sills, and thin-bedded limestone. Mineralization occurs as stratiform sheet-like and tabular orebodies hosted mainly by greenschist metamorphosed feldspathic and quartz feldspathic sandstone, basalt, and pelites. The basalts of the Surian complex show predominantly tholeiitic to transitional affinities, with a few samples that are alkalic in composition. Primitive mantle-normalized trace and rare earth element (REE) patterns of the Surian basalts display depletions in light REE, negative anomalies of Nb, Ta, and Ti, and positive anomalies of P. Positive P anomalies are indicative of minor crustal contamination. Furthermore, Th enrichments in the mid-ocean ridge basalt-normalized patterns of the Surian basalts are characteristic of rifted arc basalts emplaced in continental margin subduction zones. The high MgO content (&gt;6 wt.%) of most Surian basalts and low TiO2 content of two samples (0.53 and 0.62 wt.%) are characteristic of boninites. The aforementioned features of the basalts indicate arc tholeiites emplaced in intra-arc rift environments and continental margin subduction zones. U–Pb dating by laser ablation- inductively coupled plasma mass spectrometry of detrital zircons extracted from the host feldspathic and quartz feldspathic sandstone yields various ages that are predominantly Permian and Triassic; however, the youngest zircons give a mean Early Jurassic concordant U–Pb age of 191 ± 12 Ma. This age, together with geological and petrochemical data, indicate that VMS mineralization formed in the Early Jurassic in pull-apart basins within the SSZ. These basins and the VMS mineralization may be temporally related to an intra-arc volcano–plutonic event associated with Neo-Tethyan oblique subduction.
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ABSTRACT The effects of laser type (Nd:YAG and excimer lasers) and their analytical parameters on 34S/32S isotopic fractionation during LA-ICP-MS analysis were investigated. Laser fluence has a larger fractionation effect when ablating... more
ABSTRACT The effects of laser type (Nd:YAG and excimer lasers) and their analytical parameters on 34S/32S isotopic fractionation during LA-ICP-MS analysis were investigated. Laser fluence has a larger fractionation effect when ablating pyrite with the New Wave Nd:YAG 193 nm laser, compared to the Resonetics 193 nm excimer laser which did not produce significant fractionation over the same range of fluence (1.3-3.7 J cm−2). Matrix effects occurred between pyrite and bornite on both laser systems, especially at low fluence. However, matrix effects can be reduced with increasing fluence lessening the need for matrix matched reference materials. The effects of interface tubing configuration were also investigated and the addition of a ‘squid’ mixing device, a coil of small diameter Tygon tubing and a small volume glass bulb, was found to improve signal precision and reproducibility and decrease the washout time of the S signal between analyses. The degassing of air from the inner surfaces of the interface tubing can produce significant isotopic drift (8‰ h−1), hence flushing the tubing prior to analyses is crucial for reproducible analyses. The isotopic composition and homogeneity of a range of sulphide minerals were characterised for use as potential reference materials. We present preliminary data for a large, isotopically homogeneous pyrite crystal (PPP-1) which could be considered as a new isotopic reference material (δ34SV-CDT = 5.3 ± 0.2‰).
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ABSTRACT Morphological and geochemical analyses of blue sapphires from the Nsanaragati alluvial gem deposits in the south-western region of Cameroon help to characterize these sapphires, and constrain their source parameters. The gem... more
ABSTRACT Morphological and geochemical analyses of blue sapphires from the Nsanaragati alluvial gem deposits in the south-western region of Cameroon help to characterize these sapphires, and constrain their source parameters. The gem corundums range in color from pale to dark blue, with rare orange brown. They range from transparent to opaque, with most of the pale blue sapphires being transparent and the dark blue and orange-brown sapphires being opaque. The shape of the sapphires ranges from equant sub-platy to sub-prismatic and are sub-rounded to well-rounded. Very few of these sapphires are round and frosted. The angular lustrous sapphires are associated with a more proximal origin, while, the sub-rounded lustrous grains are either from a distal origin or more reworked. The round frosted grains may include wind worn products from eolian erosion. The LA-ICP-MS geochemical analysis of the sapphires shows minor and trace element enrichments among the identified elements. The main elemental contributions include, Fe (2496–4643 ppm), Ti (49–7069 ppm), Ca (360–976 ppm), Si (485–687 ppm) and Ga (149–307 ppm) while V (4–41 ppm) and Mg (2–42 ppm) levels are relatively low, and the remaining element values are less than 9 ppm or below their detection limits. Among element ratios, Fe/Mg (96.8–1106.8), Fe/Ti (0.5–81.5), Ti/Mg (14.5–174.1) and Ga/Mg (6.2–89.3) range into high values, while Cr/Ga (&lt;0.01) is very low. The high Fe and Ga and low Mg and Cr values suggest a magmatic origin for these sapphires, possibly xenocrysts from basaltic magmas. They were potentially crystallized from a Ga- and Fe-enriched aluminous alkaline magma.
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Research Interests: Geology, Geochemistry, Geophysics, Lao PDR, Gondwana, and 3 morePermian, Early Permian, and Elsevier
ABSTRACT The Tam Ky-Phuoc Son Shear Zone (TKPSSZ) is one of the most pronounced crustal structures in central Vietnam and juxtaposes high-grade rocks of the Kontum Massif against lower grade rocks of the Truong Son Fold Belt. An internal... more
ABSTRACT The Tam Ky-Phuoc Son Shear Zone (TKPSSZ) is one of the most pronounced crustal structures in central Vietnam and juxtaposes high-grade rocks of the Kontum Massif against lower grade rocks of the Truong Son Fold Belt. An internal zone comprises highly strained rocks, including ultramafic–mafic tectonites, bounded by mylonitic zones that straddle tens to hundreds of kilometers. An external zone comprises mainly high-grade metamorphic complexes (southern flank), and weakly metamorphosed siliciclastic and carbonate rocks with subordinate greenstone (northern flank). Detailed structural analysis reveals that the shear zone is a multi-deformed terrane: D 1 produced a regional high grade schistosity and mylonitization; D 2 generated regional northwest–southeast trending fold arrays and brittle–ductile shear zones; D 3 locally produced northeast-trending folds; brittle faulting occurred during D 4 –D 5 . U–Pb dating of zircon and monazite suggests that D 1 involved metamorphism and felsic magmatism at ca. 430 Ma, recording part of a regional collisional orogeny. Monazite and titanite growth at ca. 250–240 Ma in basement rocks is synchronous with widespread syn-to post-D 2 magmatism between ca. 260 and 245 Ma suggesting a second major collisional event during the Indosinian Orogeny. D 3 may have occurred as part of (or soon after) this Permo-Triassic event. Deformation during post-collisional stages, perhaps in re-sponse to extrusion/wedging and oroclinal rotation of terranes, led to post-D 3 structures (D 4 –D 5). The E–W trending TKPSSZ is here shown to be a continuation of the N–S trending Po Ko Shear Zone (PKSZ). Most of the significant lode gold occurrences in central Vietnam occur along this TKPSSZ–PKSZ structure and are associated with, and controlled by, D 1 ductile to ductile–brittle high-strain zones. Mineralized later-stage structures support remobilization and reconcentration of ore during subsequent events at ca. 240 Ma (Re–Os molybdenite age). The TKPSSZ–PKSZ D 1 structure likely represents part of a paleosuture zone, marking the closure of an ancient ocean basin through terrane assembly in the Early Paleozoic.
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ABSTRACT LA-ICP-MS U–Pb zircon dating reveals that the Phu Kham adakites in the Truong Son Belt were emplaced during the Late Carboniferous (ca. 306 to 304 Ma), whereas the Puthep 1 (PUT 1) adakites in the Loei Fold Belt were formed... more
ABSTRACT LA-ICP-MS U–Pb zircon dating reveals that the Phu Kham adakites in the Truong Son Belt were emplaced during the Late Carboniferous (ca. 306 to 304 Ma), whereas the Puthep 1 (PUT 1) adakites in the Loei Fold Belt were formed during the Middle Triassic (ca. 244 to 241 Ma). These rock formation ages are largely coeval to Re–Os molybdenite ages (Phu Kham: ca. 304 Ma; PUT 1: ca. 246 Ma), suggesting close temporal links between adakite formation and copper–gold mineralization. New geochemical results show that the Phu Kham and PUT 1 adakites are characterized by low HREE and Y contents, but elevated LREE, Sr, Sr/Y, and La/Yb values. In addition, the two adakites have relatively high 143Nd/144Nd ratios (0.512648 to 0.512719), Mg# (Phu Kham: 37–68; PUT 1: 40–65), and Cr and Ni contents. These results are best interpreted as representing slab melts that have interacted with supra-subduction zone mantle wedge during ascent. Tectonically, the Phu Kham and PUT 1 adakites were most likely formed during the initiation of subduction of the Ailaoshan–Song Ma and the Main Paleo-Tethys ocean plates respectively. Close temporal relations between the adakite formation and the copper–gold mineralization suggest strong genetic links between the two in the mainland SE Asia region.
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ABSTRACT The Chatree deposit is the largest epithermal Au deposit in mainland SE Asia. Despite its economic significance, the stratigraphy, age, geochemistry and tectonic setting of the host volcanic sequence is poorly documented in the... more
ABSTRACT The Chatree deposit is the largest epithermal Au deposit in mainland SE Asia. Despite its economic significance, the stratigraphy, age, geochemistry and tectonic setting of the host volcanic sequence is poorly documented in the literature. The Chatree deposit is located between Phichit and Phetchabun provinces, central Thailand, and is hosted by Late Permian to Early Triassic volcaniclastic and volcanogenic sedimentary rocks. Detailed field mapping, U-Pb zircon dating, geochemistry and stratigraphy suggest that the volcanic sequence can be subdivided into four stratigraphic units and two volcanic suites. The Late Permian Suite 1 volcanic units are sourced from a more depleted mantle relative to the overlying Early Triassic Suite 2 volcanic units. The Late Permian units Suite 1 probably formed immediately after the beginning of subduction and at the creation of a new island arc. The less depleted Early Triassic Suite 2 units were erupted during ongoing subduction once the system had achieved a steady state. The Chatree Au mineralization appears to have occurred during the switch between the two mantle sources and this switch of magma source is marked by a mixed volcano-plutonic magmatism at the Permo-Triassic boundary (ca. 250 Ma).
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Research Interests: Earth Sciences, Geology, Geochemistry, Geophysics, Tectonics, and 3 moreGondwana, Mainland, and Metallogeny
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Off the southern margin of Tasmania is a large area of thin continental crust (South Tasman Rise and East Tasman Plateau) derived from Mesozoic Gondwana. Dredging during two scientific cruises in this area recovered metamorphic rocks at... more
Off the southern margin of Tasmania is a large area of thin continental crust (South Tasman Rise and East Tasman Plateau) derived from Mesozoic Gondwana. Dredging during two scientific cruises in this area recovered metamorphic rocks at 28 localities. Upper amphibolite facies paragneiss, from the western section of the South Tasman Rise records a Cambrian metamorphic event which is correlated
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La prise en compte des donnees cinematiques permet d'interpreter la zoneographie metamorphique et le dispositif structural du complexe de haute pression Eocene superieur du Nord de la Nouvelle-Caledonie par une evolution en trois... more
La prise en compte des donnees cinematiques permet d'interpreter la zoneographie metamorphique et le dispositif structural du complexe de haute pression Eocene superieur du Nord de la Nouvelle-Caledonie par une evolution en trois temps: (1) introduction d'elements de croute continentale amincie dans une zone de subduction; (2) blocage de la subduction par epaississement crustal; (3) retour a l'equilibre gravitaire par amincissement tectonique et remontee « diapirique » du noyau eclogitique. Un tel modele rend compte des donnees thermobarometriques et radiochronologiques, de meme que de la faiblesse des deformations de substratum et l'absence de semelle metamorphique lors de la mise en place de la nappe ophiolitique.
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Igneous rocks with high Ta concentrations share a number of similarities such as high Ta/Nb, low Ti, LREE and Zr concentrations and granitic compositions. These features can be traced through fractionated granitic series. Formation of... more
Igneous rocks with high Ta concentrations share a number of similarities such as high Ta/Nb, low Ti, LREE and Zr concentrations and granitic compositions. These features can be traced through fractionated granitic series. Formation of Ta-rich melts begins with anatexis in the presence of residual biotite, followed by magmatic crystallization of biotite and muscovite. Crystallization of biotite and muscovite increases Ta/Nb and reduces the Ti content of the melt. Titanium-bearing oxides such as rutile and titanite are enriched in Ta and have the potential to deplete Ta at early stages of fractionation. However, mica crystallization suppresses their saturation and allows Ta to increase in the melt. Saturation with respect to Ta and Nb minerals occurs at the latest stages of magmatic crystallization, and columbite can originate from recrystallization of mica. We propose a model for prediction of intrusion fertility for Ta.
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We report new Ar–Ar and U–Pb ages from ten rocks in the SW Pacific region. Our results (1) establish a northward Late Miocene Australian plate movement rate of 57 mm/a for the Lord Howe hotspot chain; (2) reinforce the previously... more
We report new Ar–Ar and U–Pb ages from ten rocks in the SW Pacific region. Our results (1) establish a northward Late Miocene Australian plate movement rate of 57 mm/a for the Lord Howe hotspot chain; (2) reinforce the previously established widespread nature of Early Miocene subduction-related volcanism in onland and nearshore northern New Zealand; (3) indicate that leucotonalite xenoliths from
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... Geochemistry and tectonic significance of basalts in the Poya Terrane, New Caledonia a* JeanPhilippe Elssen ' , Anthony J. Crawford b ... Poya Terrane sequences are dominated by lowgrade metamorphosed, often tectonized, pil lowed... more
... Geochemistry and tectonic significance of basalts in the Poya Terrane, New Caledonia a* JeanPhilippe Elssen ' , Anthony J. Crawford b ... Poya Terrane sequences are dominated by lowgrade metamorphosed, often tectonized, pil lowed hasalts, with associated hyaloclastites, fine ...
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ABSTRACT Detrital zircons from samples of Palaeozoic to Mesozoic sedimentary rocks have been collected in Malaysia, Thailand, Laos, Vietnam, Cambodia and China, dated by the LA ICPMS, U–Pb technique and assigned to tectonic terranes or... more
ABSTRACT Detrital zircons from samples of Palaeozoic to Mesozoic sedimentary rocks have been collected in Malaysia, Thailand, Laos, Vietnam, Cambodia and China, dated by the LA ICPMS, U–Pb technique and assigned to tectonic terranes or regions within terranes. The combined results from each region or terrane are compared with published detrital zircon age data from Australia, Asia and elsewhere using Kolmogorov–Smirnov (K–S) statistics. Generally low P-values (probability values) are found when comparing terranes, possibly because each large terrane sourced zircons from different areas. However, very high P-values obtained in this study suggest that the Indochina terranes (Truong Son, Loei and Central Vietnam), southern China terranes (Ailaoshan, NE Vietnam, Yangtze) and the Tethyan Himalayas may have been close to similar source areas. This supports models that place South China and the Indochina terranes close to the western Himalayas. The Early Palaeozoic palaeobiogeographic data and single sample K–S comparisons from the Himalayas and from Australia suggest that North China was close to Gondwana, but our K–S inter-terrane comparisons do not support this hypothesis. High Kolmogorov–Smirnov P-values of 0.895 are found between the Late Cambrian–Early Ordovician Tarutao For- mation of Sibumasu and the Ordovician Tumblagooda Sandstone Fm of Western Australia. High P values of 0.925 and 0.958 are also found between the Tethyan Himalaya and the Tarutao Formation. Visual comparisons of proba- bility plots of zircons from quartzite clasts from the Tarutao Formation and from quartzite and granite clasts in Permian glacimarine mudstones (Kaeng Krachan Group, Sibumasu) have age spectra in common with terranes of western and northern Australia particularly the Meso-Neoproterozoic-age Pinjarra–East Antarctic–Eastern Ghats Orogen and the northern Australian area affected by the c.1850 Ma Barramundi Orogeny. A characteristic wide- spread assemblage of zircons previously recognized along the length of the Himalayas by Myrow et al. (2010) with a dominant peak at 950 Ma and other peaks at 600 Ma (Pan African Orogeny), at 1200–1000 Ma (Grenvillian Orogeny) and at 2500 Ma are also found in the peri-Gondwana Terranes of Truong Son, South China, Qiangtang, Lhasa and Sibumasu and suggest a common distal source region in the Pinjarra–East Antarctic–Eastern Ghats Orogen. The formations of the Triassic Lampang and Song Groups of northern Thailand are dated using zircons and their detrital zircons suggest probable sources from the Indochina terranes for basins of the Sukhothai Terrane.
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ABSTRACT The Western Ailaoshan (WAL) Volcanic Belts mark the western boundary of the South China–Indochina Suture Zone along the Ailaoshan Fold Belt. Geochronological and geochemical evidence suggests that the WAL Volcanic Belts vary in... more
ABSTRACT The Western Ailaoshan (WAL) Volcanic Belts mark the western boundary of the South China–Indochina Suture Zone along the Ailaoshan Fold Belt. Geochronological and geochemical evidence suggests that the WAL Volcanic Belts vary in ages and origins, and includes (1) L. Carboniferous–earliest M.-Permian (ca. 300–270 Ma) incipient backarc basin magmatism; (2) M. Permian (ca. 265 Ma) island arc/mature backarc basin magmatism; (3) early L. Permian (ca. 260–255 Ma) WAL–Indochina arc–continent collision and the associated syn-collisional granitic magmatism, as well as subsequent (4) E. Triassic (ca. 250–245 Ma) post-collisional magmatism. Regional geological comparison indicates that the post-L. Carboniferous WAL tectonic evolution was closely re-lated to the Eastern Indochina Block. We present a new G-Plate geodynamic evolution model for the Ailaoshan Fold Belt and its surrounding South China–Indochina region, based on new and published U–Pb zircon ages, to-gether with whole rock and Pb-isotope geochemical data.
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Distribution patterns, microstructural relationships, and compositional variations for framboidal pyrite in the Paleozoic sedimentary host rocks to gold deposits on the northern Carlin trend, Nevada, and at Fosterville in central... more
Distribution patterns, microstructural relationships, and compositional variations for framboidal pyrite in the Paleozoic sedimentary host rocks to gold deposits on the northern Carlin trend, Nevada, and at Fosterville in central Victoria, collectively demonstrate that it is not all of ...
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... Sebastien Meffre and Ron F. Berry. ... In the top 10 m of the ironstone (Fig. 3) the zone consists of massive to breccia-bearing, weathered, brown to red and black hematite-goethite mixtures, characterized by irregular vugs, and by... more
... Sebastien Meffre and Ron F. Berry. ... In the top 10 m of the ironstone (Fig. 3) the zone consists of massive to breccia-bearing, weathered, brown to red and black hematite-goethite mixtures, characterized by irregular vugs, and by patchy vug and fracture infill by brown caliche. ...
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... Deposits. Ross R Large 1 , , Leonid Danyushevsky 1 , Chris Hollit 1 , Valeriy Maslennikov 2 , Sebastien Meffre 1 , Sarah Gilbert 1 , Stuart Bull 1 , Rob Scott 1 , Poul Emsbo 3 , Helen Thomas 1 , Bob Singh 4 and Jeffrey Foster 1 ...
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Early Ordovician (Phase 1) magmatism in the Macquarie Arc was followed by a magmatic hiatus of ∼9 million years, between late Bendigonian and early Darriwilian (i.e. between ca 475 and ca 466 Ma). Resumption of magmatism in the Middle... more
Early Ordovician (Phase 1) magmatism in the Macquarie Arc was followed by a magmatic hiatus of ∼9 million years, between late Bendigonian and early Darriwilian (i.e. between ca 475 and ca 466 Ma). Resumption of magmatism in the Middle Ordovician produced Phase 2 rocks, recorded by three major rock suites: (i) medium-K calc-alkaline lavas in the Cargo block (Molong Volcanic Belt)
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ABSTRACT The mobility, bioaccessibility and transfer pathways of metals and metalloids in estuarine sediments have been the focus of much detailed research. However, to date, few studies have examined the mineralogical siting of metals... more
ABSTRACT The mobility, bioaccessibility and transfer pathways of metals and metalloids in estuarine sediments have been the focus of much detailed research. However, to date, few studies have examined the mineralogical siting of metals and metalloids in such sediments. This is despite the fact the mineralogy of sediments is an important factor that controls which and how much of a particular metal is released to pore waters and overlying water columns. This study reports on the mineralogical siting of metals in contaminated estuarine sediments, Hobart, Australia, and aims to evaluate the mobility of metals in the contaminated substrates. Mineralogical, mineral chemical and bulk chemical analyses demonstrate that the sediments contain very high levels of several metals and metalloids. The contaminated sediments have concentrations of zinc (Zn), lead (Pb), copper (Cu) and cadmium (Cd) ranging from 0.55 to 4.23 wt%, 0.16 to 0.70 wt%, 415 to 951 mg/kg and 23 to 300 mg/kg, respectively. Franklinite and lesser sphalerite are the main repositories of Zn, whereas much of the Pb and Cu is hosted by sulfides, organic matter and undetermined iron (Fe) oxides. While the release of contaminant loads from franklinite through dissolution is likely to be insignificant, even small releases of metals from the highly contaminated sediments can still cause the deterioration of local water quality. The contaminated sediments represent long-term sources of metal pollutants, particularly Zn, to local waters. This study demonstrates that mineralogical analyses are a vital tool to recognise the potential mobility of trace metals in estuarine environments.
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TECTONIQUE/TECTONICS Point de vue sur l&amp;#x27;évolution tectonique et géodynamique de la Nouvelle-Calédonie (Pacifique, France) Dominique Cluzel, Jonathan Aitchison, Geoffrey Clarke, Sébastien Meffre et Christian Picard Résumé Le... more
TECTONIQUE/TECTONICS Point de vue sur l&amp;#x27;évolution tectonique et géodynamique de la Nouvelle-Calédonie (Pacifique, France) Dominique Cluzel, Jonathan Aitchison, Geoffrey Clarke, Sébastien Meffre et Christian Picard Résumé Le microbloc de ...
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The New Caledonia island is a patchwork of sedimentary, volcanic and ultrabasic units. The ophiolite complex consists in a main body in the south of the island and some isolated klippes located along the NW coast. This terrane thrusts the... more
The New Caledonia island is a patchwork of sedimentary, volcanic and ultrabasic units. The ophiolite complex consists in a main body in the south of the island and some isolated klippes located along the NW coast. This terrane thrusts the magmatic Poya terrane, essentially ...
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Reply to Discussion by Sadegh Mohseni and Alijan Aftabi of "Significance of apatite REE depletion and monazite inclusions in the brecciated Se-Chahun iron oxide-apatite deposit, Bafq district, Iran: Insights from paragenesis and geochemistry" by Bonyadi, Z., Davidson, G.J., Mehrabi, B., Meffre, S...more
Crawford, AJ and Duerden, PB and Meffre, S and Scott, RJ and Squire, RJ and Williams, R, Blayney-Orange District, Report on 19999 Work program-Molong Belt, CODES & Minerals Resources NSW, Hobart Tasmania, 1, 1 (2000)[Report of Restricted... more
Crawford, AJ and Duerden, PB and Meffre, S and Scott, RJ and Squire, RJ and Williams, R, Blayney-Orange District, Report on 19999 Work program-Molong Belt, CODES & Minerals Resources NSW, Hobart Tasmania, 1, 1 (2000)[Report of Restricted Access]