... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU... more ... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU 3140 CEC Center for Mineralogy Research and Collections New York State Museum Albany, New York 12230 mlupules@mail.nysed.gov ...
This First day of the field trip visits Proterozoic iron deposits at the Podunk and Skiff Mountai... more This First day of the field trip visits Proterozoic iron deposits at the Podunk and Skiff Mountain iron mines, in the eastern Adirondack Mountains of New York state. Included are roadcuts to see representative lithologies and structures in the region surrounding the iron deposits. The origin of these iron deposits has been controversial, but studies by [Foose and McLelland (1995)][1] and more recently by [McLelland et al. (2001b][1], [2001c][1]) provide strong evidence for a high-temperture, intramagmatic origin related to late stages the Lyon Mountain Granite and correlative intrusions during the latter part of the 1090 to 1030 Ma Ottawan orogeny. The great majority of the deposits consist of low Ti magnetite ore accompanied by apatite and aegerine-augite. The apatite has high concentrations of rare-earth elements (REE) indicating to [Foose and McLelland (1995)][1] that the deposits are of Kiruna (REE-Au-U-Cu) type. This is further supported by persistent sodic (i.e., albitic) alteration associated with the ores. Most of the iron ores appear to be undeformed although they may occur in strained host rocks. Deposits are intimately associated with late tectonic to post-tectonic Lyon Mountain Granitic Gneiss that was emplaced at ca. 1055 Ma, during the waning stages of the ca. 1090 to 1030 Ma Ottawan Orogeny. [1]: /gswbk/9781934969885/9781934969885/SEC1/SEC2.atom
Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer sc... more Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer scale during amphibolite facies metamorphism ca.1180 Ma. Despite there being little evidence for interaction of hydrous fluids with ores during metamorphism, such translocation distances are considered unlikely without the assistance of fluids. Measurements of Zn isotopic composition from six Balmat ore bodies that originated from the same stratigraphic level (Upper Marble Unit 6) reveal variation between ore bodies, as well as intra-ore body trends of isotopic lightening down-plunge. In general, increasing distance of remobilization correlates with decreasing &66Zn. The syn-tectonic isotopic fractionation recorded in Balmat sphalerite is interpreted to have resulted from the interaction between the ore and sulfide melts that were fluxed by H2S localized primarily in Upper Marble Unit 7 (fetid dolomite). Lighter isotopes of Zn were enriched in the melt, leaving the residual ore enriched in heavier Zn isotopes. These observations support previous petrographic evidence for the presence of anatectic melts at Balmat and help to explain the unusual scale of translocation at Balmat by fluid-assisted remobilization during which intergranular melts decreased rock competency,
... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU... more ... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU 3140 CEC Center for Mineralogy Research and Collections New York State Museum Albany, New York 12230 mlupules@mail.nysed.gov ...
Abstract Detrital zircons in quartz-rich lithologies from the deformed and metamorphosed Mesoprot... more Abstract Detrital zircons in quartz-rich lithologies from the deformed and metamorphosed Mesoproterozoic Adirondack Lowlands in northern New York, part of the Grenville Province, have been used to document sediment provenance and basin evolution, and provide initial temporal constraints on sedimentation. Despite the effects of Shawinigan (c. 1200–1150 Ma) and Elzevirian (c. 1240–1225 Ma) orogenesis, zircon grains recovered from quartz-rich lithologies from the Grenville Supergroup largely retain detrital morphology and isotopic systematics, while displaying minimal metamorphic effects. The ages obtained constrain deposition of the entire sequence between c. 1276 and 1255 Ma. Changes in provenance track the evolution of the basin from the initial rift-drift phase, foredeep development, and transition to final basin fill and response to initial pre-Elzevirian compression. The relative lack of zircons derived from the Superior Province and predominance of those from south-central Laurentia during deposition of the sequences indicates the influence of an intervening oceanic basin to the north.
Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer sc... more Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer scale during amphibolite facies metamorphism ca. 1180 Ma. Despite there being little evidence for interaction of hydrous fluids with ores during deformation, such translocation distances are considered unlikely without the assistance of fluids. Measurements of Zn isotopic composition of sphalerite from six Balmat ore bodies that originated from the same stratigraphic level (Upper Marble unit 6) reveal variation between ore bodies, as well as intra-orebody trends of isotopic lightening down plunge. In general, increasing distance of remobilization correlates with decreasing δ 66 Zn. The syn-tectonic isotopic fractionation recorded in Balmat sphalerite is interpreted to have resulted from the interaction between the ore and sulfide melts that were fluxed by H 2 S localized primarily in Upper Marble unit 7 (fetid dolomite). Lighter isotopes of Zn were enriched in the melt, leaving the residual ore enriched in heavier Zn isotopes. These observations support previous petrographic evidence for the presence of anatectic melts at Balmat and help to explain the unusual scale of translocation at Balmat by means of fluid-assisted remobilization during which intergranular melts decreased rock competency.
... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU... more ... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU 3140 CEC Center for Mineralogy Research and Collections New York State Museum Albany, New York 12230 mlupules@mail.nysed.gov ...
This First day of the field trip visits Proterozoic iron deposits at the Podunk and Skiff Mountai... more This First day of the field trip visits Proterozoic iron deposits at the Podunk and Skiff Mountain iron mines, in the eastern Adirondack Mountains of New York state. Included are roadcuts to see representative lithologies and structures in the region surrounding the iron deposits. The origin of these iron deposits has been controversial, but studies by [Foose and McLelland (1995)][1] and more recently by [McLelland et al. (2001b][1], [2001c][1]) provide strong evidence for a high-temperture, intramagmatic origin related to late stages the Lyon Mountain Granite and correlative intrusions during the latter part of the 1090 to 1030 Ma Ottawan orogeny. The great majority of the deposits consist of low Ti magnetite ore accompanied by apatite and aegerine-augite. The apatite has high concentrations of rare-earth elements (REE) indicating to [Foose and McLelland (1995)][1] that the deposits are of Kiruna (REE-Au-U-Cu) type. This is further supported by persistent sodic (i.e., albitic) alteration associated with the ores. Most of the iron ores appear to be undeformed although they may occur in strained host rocks. Deposits are intimately associated with late tectonic to post-tectonic Lyon Mountain Granitic Gneiss that was emplaced at ca. 1055 Ma, during the waning stages of the ca. 1090 to 1030 Ma Ottawan Orogeny. [1]: /gswbk/9781934969885/9781934969885/SEC1/SEC2.atom
Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer sc... more Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer scale during amphibolite facies metamorphism ca.1180 Ma. Despite there being little evidence for interaction of hydrous fluids with ores during metamorphism, such translocation distances are considered unlikely without the assistance of fluids. Measurements of Zn isotopic composition from six Balmat ore bodies that originated from the same stratigraphic level (Upper Marble Unit 6) reveal variation between ore bodies, as well as intra-ore body trends of isotopic lightening down-plunge. In general, increasing distance of remobilization correlates with decreasing &66Zn. The syn-tectonic isotopic fractionation recorded in Balmat sphalerite is interpreted to have resulted from the interaction between the ore and sulfide melts that were fluxed by H2S localized primarily in Upper Marble Unit 7 (fetid dolomite). Lighter isotopes of Zn were enriched in the melt, leaving the residual ore enriched in heavier Zn isotopes. These observations support previous petrographic evidence for the presence of anatectic melts at Balmat and help to explain the unusual scale of translocation at Balmat by fluid-assisted remobilization during which intergranular melts decreased rock competency,
... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU... more ... Dr. Marian Lupulescu is curator of geology at the New York State Museum. ... MARIAN LUPULESCU 3140 CEC Center for Mineralogy Research and Collections New York State Museum Albany, New York 12230 mlupules@mail.nysed.gov ...
Abstract Detrital zircons in quartz-rich lithologies from the deformed and metamorphosed Mesoprot... more Abstract Detrital zircons in quartz-rich lithologies from the deformed and metamorphosed Mesoproterozoic Adirondack Lowlands in northern New York, part of the Grenville Province, have been used to document sediment provenance and basin evolution, and provide initial temporal constraints on sedimentation. Despite the effects of Shawinigan (c. 1200–1150 Ma) and Elzevirian (c. 1240–1225 Ma) orogenesis, zircon grains recovered from quartz-rich lithologies from the Grenville Supergroup largely retain detrital morphology and isotopic systematics, while displaying minimal metamorphic effects. The ages obtained constrain deposition of the entire sequence between c. 1276 and 1255 Ma. Changes in provenance track the evolution of the basin from the initial rift-drift phase, foredeep development, and transition to final basin fill and response to initial pre-Elzevirian compression. The relative lack of zircons derived from the Superior Province and predominance of those from south-central Laurentia during deposition of the sequences indicates the influence of an intervening oceanic basin to the north.
Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer sc... more Shear zone-hosted ore bodies at the Balmat, NY, zinc deposit were remobilized at the kilometer scale during amphibolite facies metamorphism ca. 1180 Ma. Despite there being little evidence for interaction of hydrous fluids with ores during deformation, such translocation distances are considered unlikely without the assistance of fluids. Measurements of Zn isotopic composition of sphalerite from six Balmat ore bodies that originated from the same stratigraphic level (Upper Marble unit 6) reveal variation between ore bodies, as well as intra-orebody trends of isotopic lightening down plunge. In general, increasing distance of remobilization correlates with decreasing δ 66 Zn. The syn-tectonic isotopic fractionation recorded in Balmat sphalerite is interpreted to have resulted from the interaction between the ore and sulfide melts that were fluxed by H 2 S localized primarily in Upper Marble unit 7 (fetid dolomite). Lighter isotopes of Zn were enriched in the melt, leaving the residual ore enriched in heavier Zn isotopes. These observations support previous petrographic evidence for the presence of anatectic melts at Balmat and help to explain the unusual scale of translocation at Balmat by means of fluid-assisted remobilization during which intergranular melts decreased rock competency.
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