<p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive... more <p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonic, metamorphic, and climatic processes, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (3,626/4,471 results for the search term <em>detrital geochronology</em> also contain the term <em>zircon U-Pb</em>; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (<em>e.g.</em>, Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (<em>e.g.</em>, Campbell <em>et al.</em>, 2005).</p><p>Therefore, it is desirable to develop complementary provenance tools for metamorphic settings. Garnet group minerals are rock-forming in several common metamorphic lithologies, and garnet is therefore a common constituent of clastic detritus from orogens. Moreover, single-grain <em>in-situ</em> dating of garnet by LA-ICPMS is possible using the U-Pb (<em>e.g.</em>, Seman <em>et al.</em>, 2017) and, by use of an online reaction cell, the Lu-Hf radioisotope systems (Simpson <em>et al.</em>, 2021).    </p><p>Here, we present results from U-Pb and Lu-Hf double-dating, acquired by LA-ICPMS for detrital garnet recovered from the Oligo-Miocene pro-foreland basin of the European Alps, as well as modern Alpine river sediment. We integrate these data with compositional data acquired by Raman spectroscopy, and energy and wavelength-dispersive X-ray spectroscopy (Stutenbecker <em>et al.</em>, 2019). We discuss the implications for Alpine tectonics and metamorphism, and future scope of detrital garnet geochronometry.   </p><p>Campbell, I., <em>et al.</em>, 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043</p><p>Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035</p><p>Seman, S., <em>et al.</em>, 2017. Chem. Geol. 460, 106–116. doi: 10.1016/j.chemgeo.2017.04.020</p><p>Simpson, A., <em>et al.</em>, 2021. Chem. Geol. 577, 120299. doi: 10.1016/j.chemgeo.2021.120299</p><p>Stutenbecker, L., <em>et al.</em>, 2019, Solid Earth 10, 1581–1595, doi: 10.5194/se-10-1581-2019</p>
Detrital geochronology employing the widely‐used zircon U‐Pb proxy is biased toward igneous event... more Detrital geochronology employing the widely‐used zircon U‐Pb proxy is biased toward igneous events and metamorphic anatexis; additionally, zircon is highly refractory and frequently polycyclic. Garnet, a rock‐forming and thus commonly occurring mineral, is predominantly metamorphic and much less refractory. Here, we report in situ U‐Pb and Lu‐Hf ages from detrital garnet hosted in ancient and modern sediments of the European Alps. Both geochronometers are biased toward the most recent garnet‐crystallizing metamorphic event in the source area, with fewer inherited ages. This likely reflects efficient removal of inherited garnet during diagenesis and metamorphism, and is in contrast to detrital zircon, apatite, and rutile U‐Pb data, which largely record pre‐Alpine ages. Neither the U‐Pb nor Lu‐Hf system in garnet exhibits a relationship between age recovery and composition. However, the Lu‐Hf system in garnet yields significantly better age recovery than the U‐Pb system. Estimated ini...
This study illustrates the clay mineralogy and sedimentary geochemistry of the Red River and its ... more This study illustrates the clay mineralogy and sedimentary geochemistry of the Red River and its major tributaries and distributaries in northern Vietnam and shows how these methods can be used to unravel grain size, provenance, hydraulic-sorting, and chemical weathering effects. All sand samples are SiO2-rich and consequently depleted in most chemical elements (but Sn and Pb) relative to the upper continental crust (UCC). The order of element mobility indicated by αAlE values, which estimate the degree of depletion in mobile element E relative to the UCC standard, is Ca ≥ Na > Sr > Mg > Ba ≥ K ≥ Rb. In mud fractions, SiO2 decreases, and other elements consequently increase. The grain size-dependent intrasample chemical variability of fluvial sediments reflects the grain size distribution of detrital minerals, which is strictly controlled in turn by the settling-equivalence principle. The 87Sr/86Sr ratio in Red River sands varies widely between 0.716 and 0.748, and εNd rang...
Geological Society, London, Special Publications, 2019
This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt (r... more This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt (representing c. 50% of world's sediments) sediments to obtain quantitative data as efficiently as for sand-sized sediments. The analytical workflows include heavy mineral separation using a wide grain-size window (15–355 μ) analysed through integrated optical analysis, Raman spectroscopy, QEMSCAN microscopy and U–Pb dating of detrital zircon. Upper Jurassic–Cretaceous silt-sized sediments from the Mandawa Basin of central-southern Tanzania have been selected for the scope of this research. Raman-aided heavy mineral analysis reveals garnet and apatite to be the most common minerals together with durable zircon, tourmaline and subordinate rutile. Accessory but diagnostic phases are titanite, staurolite, epidote and monazite. Etch pits on garnet and cockscomb features on staurolite document the significant effect of diagenesis on the pristine heavy mineral assemblage. Multivariate statis...
Title: Quantitative Provenance Analysis of Heavy Minerals through Automated Raman Spectroscopy as... more Title: Quantitative Provenance Analysis of Heavy Minerals through Automated Raman Spectroscopy as a New Tool for the Petroleum Industry Abstract: Quantitative provenance models, which relate vertical and/or lateral compositional trends within basin fills to the tectonic evolution of a source terrain, to (base-level induced) changes in sediment dispersal patterns, or to palaeoclimate fluctuations, are still in their infancy. Development and application of such models is the domain of quantitative provenance analysis (QPA); the quantitative assessment of the type, amount and rate of supply of detrital material from identifiable parent-rock assemblages to a basin fill. Despite the efforts of many, traditional heavy mineral separation and point-count methods have always been qualitative to semi-quantitative techniques, the success of which was tied to the occurrence of particularly diagnostic grains (e.g. Cr-spinel, xenotime, monazite) and biased by counts from different operators. Heav...
We here present the first comprehensive provenance study of the Zambezi deep-sea fan, based on in... more We here present the first comprehensive provenance study of the Zambezi deep-sea fan, based on integrated petrographic, heavy-mineral, elemental-geochemistry, isotope-geochemistry, and detrital-zircon-geochronology analyses of middle Pleistocene to Holocene turbidites. The Zambezi Valley and Fan represent the submarine part of an ∼ 5000-km-long sediment-routing system, extending from the heart of the South African Plateau to the abyssal depths of the Indian Ocean. Sediment is derived not only from the African side, but also from Madagascar Island mostly via the Tsiribihina Valley. Being shed by two dissected rifted margins, detritus supplied from opposite sides of the Mozambique Channel shares similar feldspar-rich feldspatho-quartzose composition, although with significant differences in heavy-mineral and geochemical signatures. The εNd values of Madagascar sand are markedly more negative and TNd model ages notably older. Zircon grains yield mostly Irumide (late Stenian) U-Pb ages ...
The deposits of large Asian rivers with unique drainage geometries have attracted considerable at... more The deposits of large Asian rivers with unique drainage geometries have attracted considerable attention due to their explanatory power concerning tectonism, surface uplift and upstream drainage evolution. This study presents the first petrographic, heavy mineral, Nd and Sr isotope geochemistry, and detrital zircon geochronology results from the Holocene Irrawaddy megadelta alongside modern and ancient sedimentary provenance datasets to assess the late Neogene evolution of the Irrawaddy River. Contrary to models advocating a steady post-middle Miocene river, we reveal an evolution of the Irrawaddy River more compatible with regional evidence for kinematic reorganization in Myanmar during late-stage India-Asia collision. Quaternary sediments are remarkably consistent in terms of provenance but highlight significant decoupling amongst fine and coarse fraction 87 Sr/ 86 Sr and ε Nd due to hydraulic sorting. Only well after the late Miocene do petrographic, heavy mineral, isotope geochemistry, and detrital zircon U-Pb results from the trunk Irrawaddy and its tributaries achieve modern-day signatures. The primary driver giving rise to the geometry and provenance signature of the modern Irrawaddy River was regional late Miocene (≤10 Ma) basin inversion coupled with uplift and cumulative displacement along the Sagaing Fault. Middle to late Miocene provenance signatures cannot be reconciled with modern river geometries, and thus require significant loss of headwaters feeding the Chindwin subbasin after ∼14 Ma and the northern Shwebo subbasin after ∼11 Ma. Large-scale reworking after ∼7 Ma is evidenced by modern Irrawaddy River provenance, by entrenchment of the nascent drainage through Plio-Pleistocene inversion structures, and in the transfer of significant sediment volumes to the Andaman Sea.
<p>Detrital geochronology is a powerful tool to interrogate the sedimentary... more <p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonic, metamorphic, and climatic processes, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (3,626/4,471 results for the search term <em>detrital geochronology</em> also contain the term <em>zircon U-Pb</em>; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (<em>e.g.</em>, Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (<em>e.g.</em>, Campbell <em>et al.</em>, 2005).</p><p>Therefore, it is desirable to develop complementary provenance tools for metamorphic settings. Garnet group minerals are rock-forming in several common metamorphic lithologies, and garnet is therefore a common constituent of clastic detritus from orogens. Moreover, single-grain <em>in-situ</em> dating of garnet by LA-ICPMS is possible using the U-Pb (<em>e.g.</em>, Seman <em>et al.</em>, 2017) and, by use of an online reaction cell, the Lu-Hf radioisotope systems (Simpson <em>et al.</em>, 2021).    </p><p>Here, we present results from U-Pb and Lu-Hf double-dating, acquired by LA-ICPMS for detrital garnet recovered from the Oligo-Miocene pro-foreland basin of the European Alps, as well as modern Alpine river sediment. We integrate these data with compositional data acquired by Raman spectroscopy, and energy and wavelength-dispersive X-ray spectroscopy (Stutenbecker <em>et al.</em>, 2019). We discuss the implications for Alpine tectonics and metamorphism, and future scope of detrital garnet geochronometry.   </p><p>Campbell, I., <em>et al.</em>, 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043</p><p>Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035</p><p>Seman, S., <em>et al.</em>, 2017. Chem. Geol. 460, 106–116. doi: 10.1016/j.chemgeo.2017.04.020</p><p>Simpson, A., <em>et al.</em>, 2021. Chem. Geol. 577, 120299. doi: 10.1016/j.chemgeo.2021.120299</p><p>Stutenbecker, L., <em>et al.</em>, 2019, Solid Earth 10, 1581–1595, doi: 10.5194/se-10-1581-2019</p>
In this study, we use provenance analysis to shed light on the Neogene evolution of river drainag... more In this study, we use provenance analysis to shed light on the Neogene evolution of river drainage and sediment dispersal in eastern Asia as a consequence of the Himalayan orogeny and topographic rise of the Tibetan Plateau. As an attempt to envisage how sediment‐routing systems operated in the past, and to identify the ultimate source of siliciclastic detritus originally generated in mainland China and now incorporated in, and recycled from, the western Taiwan accretionary prism, we have used Raman spectroscopy of detrital garnet in modern river sands and upper Neogene sandstones, complemented by detrital‐zircon geochronology and by petrographic and heavy‐mineral analysis. Garnet grains are relatively abundant and largely represented by almandine with various percentages of pyrope molecules in Yangtze sand as in western Taiwan sandstones and modern river sand derived from them. Instead, they are rare and largely represented by grossular or andradite in the sand of the Pearl River and of coastal rivers of SE China facing the Taiwan Strait. This finding supports the result of detrital geochronology, which documents a sharp difference between U‐Pb age spectra of Pearl River and coastal SE China zircons (characterised by a Paleozoic‐Mesozoic triple peak) and Yangtze and western Taiwan zircons (characterised by prominent Neoproterozoic, Paleoproterozoic, and latest Archean clusters). The Pearl River and minor rivers facing the Taiwan Strait are thus ruled out as ultimate sources of upper Neogene sandstones exposed today along the western front of the Taiwan fold‐thrust belt. In the envisaged scenario, sand mostly supplied by the paleo‐Yangtze River was entrained for ~ca.1,000 km southward by longshore currents and deposited on the Chinese passive margin before being accreted along the front of the Taiwan orogen since ~6 Ma. Littoral sand drift represents a major factor of long‐distance sediment transport in modern shelves and needs to be taken into full account in source‐to‐sink studies and paleogeographic reconstructions.
The Congo deep-sea fan, the largest on Earth fed entirely with anorogenic detritus, is characteri... more The Congo deep-sea fan, the largest on Earth fed entirely with anorogenic detritus, is characterized by quartzose to pure quartzose sand, reflecting multiple recycling coupled with extreme chemical weathering in cratonic equatorial Africa. The very youthful lower course of the Congo River connects directly to a steep canyon, where detritus including quartz grains up to a few millimeters in diameter is funneled towards Atlantic Ocean floors and deposited at abyssal depths more than a thousand kilometers away from shore. This article illustrates for the first time in detail the mineralogical and geochemical signatures of Congo Fan sands and discusses the factors controlling their intersample and intrasample variability as a key to understand how sediment is generated, recycled, and finally transferred to the deep sea. Compositional variability is largely grain-size-dependent. Combined petrographic and Raman spectroscopy analyses demonstrate that quartz increases in coarser samples and...
<p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive... more <p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonic, metamorphic, and climatic processes, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (3,626/4,471 results for the search term <em>detrital geochronology</em> also contain the term <em>zircon U-Pb</em>; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (<em>e.g.</em>, Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (<em>e.g.</em>, Campbell <em>et al.</em>, 2005).</p><p>Therefore, it is desirable to develop complementary provenance tools for metamorphic settings. Garnet group minerals are rock-forming in several common metamorphic lithologies, and garnet is therefore a common constituent of clastic detritus from orogens. Moreover, single-grain <em>in-situ</em> dating of garnet by LA-ICPMS is possible using the U-Pb (<em>e.g.</em>, Seman <em>et al.</em>, 2017) and, by use of an online reaction cell, the Lu-Hf radioisotope systems (Simpson <em>et al.</em>, 2021).    </p><p>Here, we present results from U-Pb and Lu-Hf double-dating, acquired by LA-ICPMS for detrital garnet recovered from the Oligo-Miocene pro-foreland basin of the European Alps, as well as modern Alpine river sediment. We integrate these data with compositional data acquired by Raman spectroscopy, and energy and wavelength-dispersive X-ray spectroscopy (Stutenbecker <em>et al.</em>, 2019). We discuss the implications for Alpine tectonics and metamorphism, and future scope of detrital garnet geochronometry.   </p><p>Campbell, I., <em>et al.</em>, 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043</p><p>Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035</p><p>Seman, S., <em>et al.</em>, 2017. Chem. Geol. 460, 106–116. doi: 10.1016/j.chemgeo.2017.04.020</p><p>Simpson, A., <em>et al.</em>, 2021. Chem. Geol. 577, 120299. doi: 10.1016/j.chemgeo.2021.120299</p><p>Stutenbecker, L., <em>et al.</em>, 2019, Solid Earth 10, 1581–1595, doi: 10.5194/se-10-1581-2019</p>
Detrital geochronology employing the widely‐used zircon U‐Pb proxy is biased toward igneous event... more Detrital geochronology employing the widely‐used zircon U‐Pb proxy is biased toward igneous events and metamorphic anatexis; additionally, zircon is highly refractory and frequently polycyclic. Garnet, a rock‐forming and thus commonly occurring mineral, is predominantly metamorphic and much less refractory. Here, we report in situ U‐Pb and Lu‐Hf ages from detrital garnet hosted in ancient and modern sediments of the European Alps. Both geochronometers are biased toward the most recent garnet‐crystallizing metamorphic event in the source area, with fewer inherited ages. This likely reflects efficient removal of inherited garnet during diagenesis and metamorphism, and is in contrast to detrital zircon, apatite, and rutile U‐Pb data, which largely record pre‐Alpine ages. Neither the U‐Pb nor Lu‐Hf system in garnet exhibits a relationship between age recovery and composition. However, the Lu‐Hf system in garnet yields significantly better age recovery than the U‐Pb system. Estimated ini...
This study illustrates the clay mineralogy and sedimentary geochemistry of the Red River and its ... more This study illustrates the clay mineralogy and sedimentary geochemistry of the Red River and its major tributaries and distributaries in northern Vietnam and shows how these methods can be used to unravel grain size, provenance, hydraulic-sorting, and chemical weathering effects. All sand samples are SiO2-rich and consequently depleted in most chemical elements (but Sn and Pb) relative to the upper continental crust (UCC). The order of element mobility indicated by αAlE values, which estimate the degree of depletion in mobile element E relative to the UCC standard, is Ca ≥ Na > Sr > Mg > Ba ≥ K ≥ Rb. In mud fractions, SiO2 decreases, and other elements consequently increase. The grain size-dependent intrasample chemical variability of fluvial sediments reflects the grain size distribution of detrital minerals, which is strictly controlled in turn by the settling-equivalence principle. The 87Sr/86Sr ratio in Red River sands varies widely between 0.716 and 0.748, and εNd rang...
Geological Society, London, Special Publications, 2019
This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt (r... more This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt (representing c. 50% of world's sediments) sediments to obtain quantitative data as efficiently as for sand-sized sediments. The analytical workflows include heavy mineral separation using a wide grain-size window (15–355 μ) analysed through integrated optical analysis, Raman spectroscopy, QEMSCAN microscopy and U–Pb dating of detrital zircon. Upper Jurassic–Cretaceous silt-sized sediments from the Mandawa Basin of central-southern Tanzania have been selected for the scope of this research. Raman-aided heavy mineral analysis reveals garnet and apatite to be the most common minerals together with durable zircon, tourmaline and subordinate rutile. Accessory but diagnostic phases are titanite, staurolite, epidote and monazite. Etch pits on garnet and cockscomb features on staurolite document the significant effect of diagenesis on the pristine heavy mineral assemblage. Multivariate statis...
Title: Quantitative Provenance Analysis of Heavy Minerals through Automated Raman Spectroscopy as... more Title: Quantitative Provenance Analysis of Heavy Minerals through Automated Raman Spectroscopy as a New Tool for the Petroleum Industry Abstract: Quantitative provenance models, which relate vertical and/or lateral compositional trends within basin fills to the tectonic evolution of a source terrain, to (base-level induced) changes in sediment dispersal patterns, or to palaeoclimate fluctuations, are still in their infancy. Development and application of such models is the domain of quantitative provenance analysis (QPA); the quantitative assessment of the type, amount and rate of supply of detrital material from identifiable parent-rock assemblages to a basin fill. Despite the efforts of many, traditional heavy mineral separation and point-count methods have always been qualitative to semi-quantitative techniques, the success of which was tied to the occurrence of particularly diagnostic grains (e.g. Cr-spinel, xenotime, monazite) and biased by counts from different operators. Heav...
We here present the first comprehensive provenance study of the Zambezi deep-sea fan, based on in... more We here present the first comprehensive provenance study of the Zambezi deep-sea fan, based on integrated petrographic, heavy-mineral, elemental-geochemistry, isotope-geochemistry, and detrital-zircon-geochronology analyses of middle Pleistocene to Holocene turbidites. The Zambezi Valley and Fan represent the submarine part of an ∼ 5000-km-long sediment-routing system, extending from the heart of the South African Plateau to the abyssal depths of the Indian Ocean. Sediment is derived not only from the African side, but also from Madagascar Island mostly via the Tsiribihina Valley. Being shed by two dissected rifted margins, detritus supplied from opposite sides of the Mozambique Channel shares similar feldspar-rich feldspatho-quartzose composition, although with significant differences in heavy-mineral and geochemical signatures. The εNd values of Madagascar sand are markedly more negative and TNd model ages notably older. Zircon grains yield mostly Irumide (late Stenian) U-Pb ages ...
The deposits of large Asian rivers with unique drainage geometries have attracted considerable at... more The deposits of large Asian rivers with unique drainage geometries have attracted considerable attention due to their explanatory power concerning tectonism, surface uplift and upstream drainage evolution. This study presents the first petrographic, heavy mineral, Nd and Sr isotope geochemistry, and detrital zircon geochronology results from the Holocene Irrawaddy megadelta alongside modern and ancient sedimentary provenance datasets to assess the late Neogene evolution of the Irrawaddy River. Contrary to models advocating a steady post-middle Miocene river, we reveal an evolution of the Irrawaddy River more compatible with regional evidence for kinematic reorganization in Myanmar during late-stage India-Asia collision. Quaternary sediments are remarkably consistent in terms of provenance but highlight significant decoupling amongst fine and coarse fraction 87 Sr/ 86 Sr and ε Nd due to hydraulic sorting. Only well after the late Miocene do petrographic, heavy mineral, isotope geochemistry, and detrital zircon U-Pb results from the trunk Irrawaddy and its tributaries achieve modern-day signatures. The primary driver giving rise to the geometry and provenance signature of the modern Irrawaddy River was regional late Miocene (≤10 Ma) basin inversion coupled with uplift and cumulative displacement along the Sagaing Fault. Middle to late Miocene provenance signatures cannot be reconciled with modern river geometries, and thus require significant loss of headwaters feeding the Chindwin subbasin after ∼14 Ma and the northern Shwebo subbasin after ∼11 Ma. Large-scale reworking after ∼7 Ma is evidenced by modern Irrawaddy River provenance, by entrenchment of the nascent drainage through Plio-Pleistocene inversion structures, and in the transfer of significant sediment volumes to the Andaman Sea.
<p>Detrital geochronology is a powerful tool to interrogate the sedimentary... more <p>Detrital geochronology is a powerful tool to interrogate the sedimentary archive of (paleo-)hinterland tectonic, metamorphic, and climatic processes, and can also be applied to modern river sediment as a first-pass tool to establish regional bedrock ages. The popular zircon U-Pb detrital geochronometer has seen widespread adoption for these tasks (3,626/4,471 results for the search term <em>detrital geochronology</em> also contain the term <em>zircon U-Pb</em>; Clarivate Analytics Web of Science). However, zircon fertility is strongly biased to intermediate to felsic source rocks. Moreover, zircon crystallization is volumetrically limited in metamorphic terranes which do not achieve anataxis (<em>e.g.</em>, Moecher & Samson, 2006), and is typically restricted to rim overgrowths which are vulnerable to mechanical destruction during fluvial transport, and which are challenging to detect and analyse (<em>e.g.</em>, Campbell <em>et al.</em>, 2005).</p><p>Therefore, it is desirable to develop complementary provenance tools for metamorphic settings. Garnet group minerals are rock-forming in several common metamorphic lithologies, and garnet is therefore a common constituent of clastic detritus from orogens. Moreover, single-grain <em>in-situ</em> dating of garnet by LA-ICPMS is possible using the U-Pb (<em>e.g.</em>, Seman <em>et al.</em>, 2017) and, by use of an online reaction cell, the Lu-Hf radioisotope systems (Simpson <em>et al.</em>, 2021).    </p><p>Here, we present results from U-Pb and Lu-Hf double-dating, acquired by LA-ICPMS for detrital garnet recovered from the Oligo-Miocene pro-foreland basin of the European Alps, as well as modern Alpine river sediment. We integrate these data with compositional data acquired by Raman spectroscopy, and energy and wavelength-dispersive X-ray spectroscopy (Stutenbecker <em>et al.</em>, 2019). We discuss the implications for Alpine tectonics and metamorphism, and future scope of detrital garnet geochronometry.   </p><p>Campbell, I., <em>et al.</em>, 2005. Earth Planet. Sci. Lett. 237, 402-432,  doi: 10.1016/j.epsl.2005.06.043</p><p>Moecher, D., & Samson, S., 2006, Earth Planet. Sci. Lett. 247, 252–266, doi: 10.1016/j.epsl.2006.04.035</p><p>Seman, S., <em>et al.</em>, 2017. Chem. Geol. 460, 106–116. doi: 10.1016/j.chemgeo.2017.04.020</p><p>Simpson, A., <em>et al.</em>, 2021. Chem. Geol. 577, 120299. doi: 10.1016/j.chemgeo.2021.120299</p><p>Stutenbecker, L., <em>et al.</em>, 2019, Solid Earth 10, 1581–1595, doi: 10.5194/se-10-1581-2019</p>
In this study, we use provenance analysis to shed light on the Neogene evolution of river drainag... more In this study, we use provenance analysis to shed light on the Neogene evolution of river drainage and sediment dispersal in eastern Asia as a consequence of the Himalayan orogeny and topographic rise of the Tibetan Plateau. As an attempt to envisage how sediment‐routing systems operated in the past, and to identify the ultimate source of siliciclastic detritus originally generated in mainland China and now incorporated in, and recycled from, the western Taiwan accretionary prism, we have used Raman spectroscopy of detrital garnet in modern river sands and upper Neogene sandstones, complemented by detrital‐zircon geochronology and by petrographic and heavy‐mineral analysis. Garnet grains are relatively abundant and largely represented by almandine with various percentages of pyrope molecules in Yangtze sand as in western Taiwan sandstones and modern river sand derived from them. Instead, they are rare and largely represented by grossular or andradite in the sand of the Pearl River and of coastal rivers of SE China facing the Taiwan Strait. This finding supports the result of detrital geochronology, which documents a sharp difference between U‐Pb age spectra of Pearl River and coastal SE China zircons (characterised by a Paleozoic‐Mesozoic triple peak) and Yangtze and western Taiwan zircons (characterised by prominent Neoproterozoic, Paleoproterozoic, and latest Archean clusters). The Pearl River and minor rivers facing the Taiwan Strait are thus ruled out as ultimate sources of upper Neogene sandstones exposed today along the western front of the Taiwan fold‐thrust belt. In the envisaged scenario, sand mostly supplied by the paleo‐Yangtze River was entrained for ~ca.1,000 km southward by longshore currents and deposited on the Chinese passive margin before being accreted along the front of the Taiwan orogen since ~6 Ma. Littoral sand drift represents a major factor of long‐distance sediment transport in modern shelves and needs to be taken into full account in source‐to‐sink studies and paleogeographic reconstructions.
The Congo deep-sea fan, the largest on Earth fed entirely with anorogenic detritus, is characteri... more The Congo deep-sea fan, the largest on Earth fed entirely with anorogenic detritus, is characterized by quartzose to pure quartzose sand, reflecting multiple recycling coupled with extreme chemical weathering in cratonic equatorial Africa. The very youthful lower course of the Congo River connects directly to a steep canyon, where detritus including quartz grains up to a few millimeters in diameter is funneled towards Atlantic Ocean floors and deposited at abyssal depths more than a thousand kilometers away from shore. This article illustrates for the first time in detail the mineralogical and geochemical signatures of Congo Fan sands and discusses the factors controlling their intersample and intrasample variability as a key to understand how sediment is generated, recycled, and finally transferred to the deep sea. Compositional variability is largely grain-size-dependent. Combined petrographic and Raman spectroscopy analyses demonstrate that quartz increases in coarser samples and...
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