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Der-chuen Lee - One of the best experts on this subject based on the ideXlab platform.
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genesis of Jadeite quartz rocks in the yorii area of the kanto mountains japan
Journal of Asian Earth Sciences, 2013Co-Authors: Mayuko Fukuyama, Masatsugu Ogasawara, Kenji Horie, Der-chuen LeeAbstract:Abstract This paper reports the results of U–Pb dating and REE (rare earth element) analysis of zircons separated from Jadeite–quartz rocks within serpentinite melanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain Jadeite, albite, and quartz, with minor aegirine–augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a Jadeite + quartz = albite reaction during formation of these Jadeite–quartz rocks. Zircon crystals separated from the Jadeite–quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, Jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the Jadeite–quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U–Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino–Tanba–Chichibu accretionary complex in Japan. The age data indicate that the Jadeite–quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The Jadeite–quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be concentrated into Jadeite–quartz rocks prior to a fluid moving up into the mantle wedge. Typical arc volcanic rocks are depleted in the HFSE, suggesting that the high HFSE concentrations within Jadeite–quartz rocks are consistent with fluids being stripped of their HFSE prior to interaction with mantle material during the formation of arc magmas. Although these Jadeite-bearing rocks are rare occurrences on the surface exposure, they could be abundant in or above subducted slabs.
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Genesis of Jadeite–quartz rocks in the Yorii area of the Kanto Mountains, Japan
Journal of Asian Earth Sciences, 2013Co-Authors: Mayuko Fukuyama, Masatsugu Ogasawara, Kenji Horie, Der-chuen LeeAbstract:Abstract This paper reports the results of U–Pb dating and REE (rare earth element) analysis of zircons separated from Jadeite–quartz rocks within serpentinite melanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain Jadeite, albite, and quartz, with minor aegirine–augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a Jadeite + quartz = albite reaction during formation of these Jadeite–quartz rocks. Zircon crystals separated from the Jadeite–quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, Jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the Jadeite–quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U–Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino–Tanba–Chichibu accretionary complex in Japan. The age data indicate that the Jadeite–quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The Jadeite–quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be concentrated into Jadeite–quartz rocks prior to a fluid moving up into the mantle wedge. Typical arc volcanic rocks are depleted in the HFSE, suggesting that the high HFSE concentrations within Jadeite–quartz rocks are consistent with fluids being stripped of their HFSE prior to interaction with mantle material during the formation of arc magmas. Although these Jadeite-bearing rocks are rare occurrences on the surface exposure, they could be abundant in or above subducted slabs.
Lu Wang - One of the best experts on this subject based on the ideXlab platform.
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microfabric characteristics and rheological significance of ultra high pressure metamorphosed Jadeite quartzite and eclogite from shuanghe dabie mountains china
Journal of Metamorphic Geology, 2010Co-Authors: Lu Wang, Z M Jin, Timothy M Kusky, X W LiuAbstract:Quantitative analysis of the structural evolution of Jadeite-quartzite, a rare ultra-high pressure (UHP) rock type from the Dabie Mountains of eastern China, sheds light on the formation and evolution of UHP orogenic belts worldwide. Geological mapping of the Shuanghe area, where Jadeite-quartzites crop out, was carried out to determine the spatial relationships between different UHP rocks within this orogen. The deformation mechanisms of Jadeite-quartzite, geodynamical parameters (stress, strain, strain rate), and microstructure including lattice preferred orientation (LPO) were determined from six Jadeite-quartzite samples from the Shuanghe area. LPOs of clinopyroxene (Jadeite and omphacite), garnet, rutile and quartz from these Jadeite-quartzite samples are compared with those of three eclogites preserving different degrees of deformation from the Shuanghe area. Microstructural LPOs of Jadeite, omphacite, garnet, rutile and quartz were determined using electron backscattered diffraction (EBSD) analysis. Quartz fabrics were largely recrystallized during late, low-grade stages of deformation, whereas garnet shows no strong LPO patterns. Rutile fabrics show a weak LS fabric along (001). Jadeite and omphacite show the strongest eclogite facies LPO patterns, suggesting that they may provide important information about mantle deformation patterns and control the rheology of deeply subducted continental crust. Microstructural data show that the Jadeite LPO patterns are similar to those of omphacite and vary between L- and S-types, which correlate with prolate and oblate grain shape fabrics (SPO); quartz LPOs are monoclinic. Microstructural analysis using TEM shows that the dominant slip systems of Jadeite in one sample are (100)(001), (110)(001) and (1 1 0)1 ⁄ 2(110), while in another sample, no dislocations are observed. Abundant dislocations in quartz were accommodated by the dominant slip system (0001)(1120), indicating basal glide and represents regional shearing during the exhumation process. This suggests that dislocation creep is the dominant fundamental deformation mechanism in Jadeite under UHP conditions. The protoliths of Jadeite-quartzite, metasedimentary rocks from the northern passive continental margin of the Yangtze craton, experienced the same deep subduction and were deformed under similar rheological conditions as other UHP eclogite, marble and paragneiss. Experimental UHP deformation of quartzo-feldspathic gneiss with a chemical composition similar to the bulk continental crust has shown that the formation of a Jadeite- stishovite rock is associated with a density increase of the host rock similar to the eclogite conversion from basaltic protoliths. The resulting rock can be denser than the surrounding mantle pyrolite up to depths of 660 km (24 GPa). Thus, processes of deep continental subduction may be better-understood through understanding the rheology and mechanical behaviour of Jadeite. Jadeite-quartzites such as those from the Shuanghe may be exhumed remnants of deeply-subducted slabs of continental crust, other parts of which subducted past thedepth of no return� , and remain in the deep mantle.
X W Liu - One of the best experts on this subject based on the ideXlab platform.
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microfabric characteristics and rheological significance of ultra high pressure metamorphosed Jadeite quartzite and eclogite from shuanghe dabie mountains china
Journal of Metamorphic Geology, 2010Co-Authors: Lu Wang, Z M Jin, Timothy M Kusky, X W LiuAbstract:Quantitative analysis of the structural evolution of Jadeite-quartzite, a rare ultra-high pressure (UHP) rock type from the Dabie Mountains of eastern China, sheds light on the formation and evolution of UHP orogenic belts worldwide. Geological mapping of the Shuanghe area, where Jadeite-quartzites crop out, was carried out to determine the spatial relationships between different UHP rocks within this orogen. The deformation mechanisms of Jadeite-quartzite, geodynamical parameters (stress, strain, strain rate), and microstructure including lattice preferred orientation (LPO) were determined from six Jadeite-quartzite samples from the Shuanghe area. LPOs of clinopyroxene (Jadeite and omphacite), garnet, rutile and quartz from these Jadeite-quartzite samples are compared with those of three eclogites preserving different degrees of deformation from the Shuanghe area. Microstructural LPOs of Jadeite, omphacite, garnet, rutile and quartz were determined using electron backscattered diffraction (EBSD) analysis. Quartz fabrics were largely recrystallized during late, low-grade stages of deformation, whereas garnet shows no strong LPO patterns. Rutile fabrics show a weak LS fabric along (001). Jadeite and omphacite show the strongest eclogite facies LPO patterns, suggesting that they may provide important information about mantle deformation patterns and control the rheology of deeply subducted continental crust. Microstructural data show that the Jadeite LPO patterns are similar to those of omphacite and vary between L- and S-types, which correlate with prolate and oblate grain shape fabrics (SPO); quartz LPOs are monoclinic. Microstructural analysis using TEM shows that the dominant slip systems of Jadeite in one sample are (100)(001), (110)(001) and (1 1 0)1 ⁄ 2(110), while in another sample, no dislocations are observed. Abundant dislocations in quartz were accommodated by the dominant slip system (0001)(1120), indicating basal glide and represents regional shearing during the exhumation process. This suggests that dislocation creep is the dominant fundamental deformation mechanism in Jadeite under UHP conditions. The protoliths of Jadeite-quartzite, metasedimentary rocks from the northern passive continental margin of the Yangtze craton, experienced the same deep subduction and were deformed under similar rheological conditions as other UHP eclogite, marble and paragneiss. Experimental UHP deformation of quartzo-feldspathic gneiss with a chemical composition similar to the bulk continental crust has shown that the formation of a Jadeite- stishovite rock is associated with a density increase of the host rock similar to the eclogite conversion from basaltic protoliths. The resulting rock can be denser than the surrounding mantle pyrolite up to depths of 660 km (24 GPa). Thus, processes of deep continental subduction may be better-understood through understanding the rheology and mechanical behaviour of Jadeite. Jadeite-quartzites such as those from the Shuanghe may be exhumed remnants of deeply-subducted slabs of continental crust, other parts of which subducted past thedepth of no return� , and remain in the deep mantle.
Aral I. Okay - One of the best experts on this subject based on the ideXlab platform.
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Jadeite-K-feldspar rocks and jadeitites from Northwest Turkey
Mineralogical Magazine, 1997Co-Authors: Aral I. OkayAbstract:Blueschist-facies rocks with Jadeite-K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The Jadeite-K-feldspar rocks have a very fine grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, recognized from their characteristic shapes, are pseudomorphed by Jadeite and K-feldspar, while the relict magmatic aegirine has rims of Jadeite. The matrix of the rock consists of very fine-grained aggregates of Jadeite, K-feldspar and lawsonite. In some blocks, Jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8+ or -2 kbar and 300+ or -50 degrees C. The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that Jadeite-K-feldspar is a stable mineral pair in blueschist-facies P-T conditions.
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Jadeite-K-feldspar rocks and jadeitites northwest Turkey from
1997Co-Authors: Aral I. OkayAbstract:Blueschist-facies rocks with Jadeite--K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The Jadeite-K-feldspar rocks have a very fme grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, from their characteristic shapes, are pseudomorphed by Jadeite and K-feldspar, while the relict magrnatic aegirine has rims of Jadeite. The matrix of the rock consists of very fine-grained aggregates of Jadeite, K-feldspar and lawsonite. In some blocks, Jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8 _+ 2 kbar and 300 __+ 50~ The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that Jadeite-K-feldspar is a stable mineral pair in blueschist-facies conditions.
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Jadeite–K-feldspar rocks and jadeitites from northwest Turkey
Mineralogical Magazine, 1997Co-Authors: Aral I. OkayAbstract:AbstractBlueschist-facies rocks with Jadeite-K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The Jadeite-K-feldspar rocks have a very fine grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, recognized from their characteristic shapes, are pseudomorphed by Jadeite and K-feldspar, while the relict magmatic aegirine has rims of Jadeite. The matrix of the rock consists of very fine-grained aggregates of Jadeite, K-feldspar and lawsonite. In some blocks, Jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8 ± 2 kbar and 300 ± 50°C. The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that Jadeite-K-feldspar is a stable mineral pair in blueschist-facies P-T conditions.
Mayuko Fukuyama - One of the best experts on this subject based on the ideXlab platform.
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genesis of Jadeite quartz rocks in the yorii area of the kanto mountains japan
Journal of Asian Earth Sciences, 2013Co-Authors: Mayuko Fukuyama, Masatsugu Ogasawara, Kenji Horie, Der-chuen LeeAbstract:Abstract This paper reports the results of U–Pb dating and REE (rare earth element) analysis of zircons separated from Jadeite–quartz rocks within serpentinite melanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain Jadeite, albite, and quartz, with minor aegirine–augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a Jadeite + quartz = albite reaction during formation of these Jadeite–quartz rocks. Zircon crystals separated from the Jadeite–quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, Jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the Jadeite–quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U–Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino–Tanba–Chichibu accretionary complex in Japan. The age data indicate that the Jadeite–quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The Jadeite–quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be concentrated into Jadeite–quartz rocks prior to a fluid moving up into the mantle wedge. Typical arc volcanic rocks are depleted in the HFSE, suggesting that the high HFSE concentrations within Jadeite–quartz rocks are consistent with fluids being stripped of their HFSE prior to interaction with mantle material during the formation of arc magmas. Although these Jadeite-bearing rocks are rare occurrences on the surface exposure, they could be abundant in or above subducted slabs.
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Genesis of Jadeite–quartz rocks in the Yorii area of the Kanto Mountains, Japan
Journal of Asian Earth Sciences, 2013Co-Authors: Mayuko Fukuyama, Masatsugu Ogasawara, Kenji Horie, Der-chuen LeeAbstract:Abstract This paper reports the results of U–Pb dating and REE (rare earth element) analysis of zircons separated from Jadeite–quartz rocks within serpentinite melanges in the Yorii area of the Kanto Mountains, Japan. These rocks contain Jadeite, albite, and quartz, with minor aegirine–augite, zircon, monazite, thorite, allanite, and titanite. Mineral textures provide evidence of a Jadeite + quartz = albite reaction during formation of these Jadeite–quartz rocks. Zircon crystals separated from the Jadeite–quartz rocks can be split into two distinct types, here named Types I and II, based on their morphology and REE concentrations. Type I zircons are prismatic and have fluid, Jadeite, quartz, and albite inclusions. Those show positive Ce and negative Eu anomalies and HREE (heavy rare earth element) enriched chondrite normalized REE patterns and have higher REE concentrations than those generally found in magmatic zircons. Type I zircons would have precipitated from a fluid. Mineralogical observation provides that Type I zircon crystallized at the same timing of the formation of the Jadeite–quartz rocks. Type II zircons are porous and have REE patterns indicative of a hydrothermal zircon. Both types of zircons are fluid-related. Type I zircons yield U–Pb ages of 162.2 ± 0.6 Ma, with an MSWD (mean square weighted deviation) of 1.4. At this time, Japan was still a part of the eastern margin of the Asian continent, with the subduction of the oceanic paleo-Pacific Plate leading to the formation of the Jurassic Mino–Tanba–Chichibu accretionary complex in Japan. The age data indicate that the Jadeite–quartz rocks formed in a deep subduction zone environment at the same time as the formation of the Jurassic accretionary complex in a shallower near-trench subduction zone environment. The Jadeite–quartz rocks contain high concentrations of Zr and Nb, with low LILE (large ion lithophile elements) concentrations, suggesting that the HFSE (high field strength elements) can be concentrated into Jadeite–quartz rocks prior to a fluid moving up into the mantle wedge. Typical arc volcanic rocks are depleted in the HFSE, suggesting that the high HFSE concentrations within Jadeite–quartz rocks are consistent with fluids being stripped of their HFSE prior to interaction with mantle material during the formation of arc magmas. Although these Jadeite-bearing rocks are rare occurrences on the surface exposure, they could be abundant in or above subducted slabs.
