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J G Liou - One of the best experts on this subject based on the ideXlab platform.
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petrological and geochronological constraints on the origin of hp and uhp kyanite Quartzites from the sulu orogen eastern china
Journal of Asian Earth Sciences, 2011Co-Authors: Wei Wang, Zeming Zhang, Feng Liu, Xin Dong, J G LiouAbstract:Abstract Kyanite (Ky)-Quartzites occur in both the high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic belts in the southern Sulu orogen. The HP Ky-Quartzites consist of quartz, kyanite and minor rutile with or without topaz and phengite, whereas those from the UHP unit consist of quartz, kyanite, phengite and rutile. The HP Ky-Quartzites are characterized by high Al2O3 (up to 32.9 wt.%) and low SiO2 (down to 60.4 wt.%) with very low other oxides contents (
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p t estimates for phengite kyanite uhp eclogites from a highway roadcut near the qinglong mountains eastern china
AGUFM, 2001Co-Authors: C G Mattinson, J G Liou, A Bian, R Y Zhang, R E Jones, C Liu, J Yang, Z QinAbstract:Recent highway construction across the Qinglong Mountains in Donghai, eastern China (Figure 1) has exposed a 660 m section of gneiss, eclogite, and minor Quartzite. The outcrop consists of steeply SE-dipping layers cut by several high-angle (normal?) faults (Figure 2). Eclogite layers are concordant with gneissic rocks and minor Quartzites; a few discordant eclogite contacts (e.g., QL16) appear to be intrusive. Most eclogites are characterized by abundant hydrous phases including talc, phengite, and epidote; many also contain kyanite. The Qinglong Mountains contain a variety of UHP eclogites, and are the classic locality for negative δ18O values (-14 to -16‰) for UHP minerals in eclogites, Quartzites and surrounding gneisses (Yui et al. 1994; Rumble and Yui 1998) indicating that fluid may have been absent during metamorphism. Inclusions of coesite and coesite pseudomorphs in UHP phases, including epidote and kyanite from both eclogite and Quartzite, of this region were reported by Zhang et al. (1995; in review). This region lies about 22 km NE from the Chinese Continental Scientific Drilling site in Donghai. Therefore, petrotectonic information derived from this continuous exposure of eclogitic and gneissic rocks is applicable to the CCSD site.
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petrology geochemistry and isotope data on a ultrahigh pressure jadeite Quartzite from shuanghe dabie mountains east central china
Lithos, 1997Co-Authors: J G Liou, Ru Y Zhang, Borming JahnAbstract:Abstract In the Dabie ultrahigh-pressure terrane of east-central China, coesite-bearing jadeite Quartzites occur locally as intercalated layers with marble and mafic eclogite. This rock assemblage is, in turn, enclosed within quartzofeldspathic gneisses. Metamorphic parageneses and kelyphitic textures reveal a multistage metamorphic evolution and complex exhumation history. The primary peak metamorphic assemblage consists of jadeite + garnet + coesite + rutile ± apatite. Minor coesite and coesite pseudomorphs occur as inclusions in jadeite and garnet. Three stages of retrograde assemblages are observed in the jadeite Quartzites. Stage A is represented by the polymorphic transformation of coesite to quartz aggregates. Stage B is characterized by formation of coronas around jadeite porphyroblasts consisting of an inner layer of oligoclase + amphibole and an outer layer of albite ± aegirine—augite. The last stage (stage C) involved total replacement of jadeite and most garnets by taramitic amphibole + albite + aegirine-augite. Peak metamorphic P-T conditions were > 26 kbar at 660°C and are consistent with the estimates from the adjacent coesite-bearing eclogites. The jadeite Quartzites display clockwise P-T path that matches those of the adjacent eclogites. Major and trace element data suggest that the protolith of the jadeite Quartzite could have been an albitized siltstone enriched in Na and depleted in K and Ca. The highly negative present-day eNd value (−24.7) indicates a very old age for the protolith. Its late Archean model age (TDM) of 2.58 Ga is among the oldest so far identified for rocks from the Dabie UHPM terrane. Concordant field relations and petrogenetic considerations suggest that all mafic, politic, carbonate and gneissic rocks have experienced in-situ UHP metamorphism during Triassic continental collision between the Sino-Korean and Yangtze cratons.
Borming Jahn - One of the best experts on this subject based on the ideXlab platform.
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petrology geochemistry and isotope data on a ultrahigh pressure jadeite Quartzite from shuanghe dabie mountains east central china
Lithos, 1997Co-Authors: J G Liou, Ru Y Zhang, Borming JahnAbstract:Abstract In the Dabie ultrahigh-pressure terrane of east-central China, coesite-bearing jadeite Quartzites occur locally as intercalated layers with marble and mafic eclogite. This rock assemblage is, in turn, enclosed within quartzofeldspathic gneisses. Metamorphic parageneses and kelyphitic textures reveal a multistage metamorphic evolution and complex exhumation history. The primary peak metamorphic assemblage consists of jadeite + garnet + coesite + rutile ± apatite. Minor coesite and coesite pseudomorphs occur as inclusions in jadeite and garnet. Three stages of retrograde assemblages are observed in the jadeite Quartzites. Stage A is represented by the polymorphic transformation of coesite to quartz aggregates. Stage B is characterized by formation of coronas around jadeite porphyroblasts consisting of an inner layer of oligoclase + amphibole and an outer layer of albite ± aegirine—augite. The last stage (stage C) involved total replacement of jadeite and most garnets by taramitic amphibole + albite + aegirine-augite. Peak metamorphic P-T conditions were > 26 kbar at 660°C and are consistent with the estimates from the adjacent coesite-bearing eclogites. The jadeite Quartzites display clockwise P-T path that matches those of the adjacent eclogites. Major and trace element data suggest that the protolith of the jadeite Quartzite could have been an albitized siltstone enriched in Na and depleted in K and Ca. The highly negative present-day eNd value (−24.7) indicates a very old age for the protolith. Its late Archean model age (TDM) of 2.58 Ga is among the oldest so far identified for rocks from the Dabie UHPM terrane. Concordant field relations and petrogenetic considerations suggest that all mafic, politic, carbonate and gneissic rocks have experienced in-situ UHP metamorphism during Triassic continental collision between the Sino-Korean and Yangtze cratons.
Fang Huang - One of the best experts on this subject based on the ideXlab platform.
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fe and o isotopes in coesite bearing jadeite Quartzite from the western alps record multistage fluid rock interactions in a continental subduction zone
Geochimica et Cosmochimica Acta, 2021Co-Authors: Jiawei Xiong, Hans-peter Schertl, Yong-fei Zheng, Yi-xiang Chen, Kun Zhou, Fang HuangAbstract:Abstract Fluid is a key agent for the mass transfer between the subducting slab and the mantle wedge, which greatly affects the evolution of the crust-mantle system at convergent plate boundaries. A geochemical study was carried out for coesite-bearing jadeite Quartzite and its country rock granitic gneiss from the Dora Maira Massif in the Western Alps. The results provide new insights into the composition of metamorphic fluids and fluid-rock interaction processes in the continental subduction zone. Coesite inclusions are found for the first time in metamorphic zircons of the granitic gneiss. The ultrahigh-pressure (UHP) metamorphism was dated to occur at 34.7 ± 0.3 Ma, confirming that the country rock experienced the UHP metamorphism synchronously with the whiteschist and jadeite Quartzite. The jadeite Quartzite occurs as layers and boudins within the coesite-bearing whiteschist, and shows similar whole-rock REE distribution patterns to both granitic gneiss and whiteschist. In addition, relict domains of magmatic zircon in the three types of UHP metamorphic rocks exhibit similar U-Pb ages and δ18O values, indicating that they have the same protolith of granites. However, metamorphic zircons in the jadeite Quartzite show significantly lower δ18O values of 6.1–7.3‰ than the relict magmatic domains of 9.4–10.6‰. Furthermore, the jadeite Quartzite has whole-rock δ18O values of 7.9–8.7‰, significantly lower than those of 9.5–10.9‰ for the granitic gneiss but higher than 6.5–7.9‰ for the whiteschist. These differences suggest that the jadeite Quartzite was probably formed through metasomatism of metagranite by external fluids with relatively low δ18O values. The jadeite Quartzite shows high δ56Fe values of 0.69–0.87‰, considerably higher than those of 0.18–0.38‰ for the granitic gneiss, but falling within the range of 0.32–1.03‰ for the whiteschist from the same outcrop. The Fe isotope modeling results suggest that the metasomatic fluids responsible for the formation of jadeite Quartzite were possibly derived from the host whiteschist under UHP metamorphic conditions. Such fluids are enriched in Si, Al and Mg, and have high δ56Fe but low δ18O values. Therefore, the jadeite Quartzite records the action of metamorphic supercritical fluids at the subarc depth. If the metasomatized rocks in the continental subduction zone would dehydrate to generate fluids with variable geochemical compositions due to multistage fluid-rock interactions, the fluids could further infiltrate the surrounding rock and possibly the mantle wedge to result in further geochemical transfer from the subducting slab to the mantle wedge.
Yong-fei Zheng - One of the best experts on this subject based on the ideXlab platform.
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fe and o isotopes in coesite bearing jadeite Quartzite from the western alps record multistage fluid rock interactions in a continental subduction zone
Geochimica et Cosmochimica Acta, 2021Co-Authors: Jiawei Xiong, Hans-peter Schertl, Yong-fei Zheng, Yi-xiang Chen, Kun Zhou, Fang HuangAbstract:Abstract Fluid is a key agent for the mass transfer between the subducting slab and the mantle wedge, which greatly affects the evolution of the crust-mantle system at convergent plate boundaries. A geochemical study was carried out for coesite-bearing jadeite Quartzite and its country rock granitic gneiss from the Dora Maira Massif in the Western Alps. The results provide new insights into the composition of metamorphic fluids and fluid-rock interaction processes in the continental subduction zone. Coesite inclusions are found for the first time in metamorphic zircons of the granitic gneiss. The ultrahigh-pressure (UHP) metamorphism was dated to occur at 34.7 ± 0.3 Ma, confirming that the country rock experienced the UHP metamorphism synchronously with the whiteschist and jadeite Quartzite. The jadeite Quartzite occurs as layers and boudins within the coesite-bearing whiteschist, and shows similar whole-rock REE distribution patterns to both granitic gneiss and whiteschist. In addition, relict domains of magmatic zircon in the three types of UHP metamorphic rocks exhibit similar U-Pb ages and δ18O values, indicating that they have the same protolith of granites. However, metamorphic zircons in the jadeite Quartzite show significantly lower δ18O values of 6.1–7.3‰ than the relict magmatic domains of 9.4–10.6‰. Furthermore, the jadeite Quartzite has whole-rock δ18O values of 7.9–8.7‰, significantly lower than those of 9.5–10.9‰ for the granitic gneiss but higher than 6.5–7.9‰ for the whiteschist. These differences suggest that the jadeite Quartzite was probably formed through metasomatism of metagranite by external fluids with relatively low δ18O values. The jadeite Quartzite shows high δ56Fe values of 0.69–0.87‰, considerably higher than those of 0.18–0.38‰ for the granitic gneiss, but falling within the range of 0.32–1.03‰ for the whiteschist from the same outcrop. The Fe isotope modeling results suggest that the metasomatic fluids responsible for the formation of jadeite Quartzite were possibly derived from the host whiteschist under UHP metamorphic conditions. Such fluids are enriched in Si, Al and Mg, and have high δ56Fe but low δ18O values. Therefore, the jadeite Quartzite records the action of metamorphic supercritical fluids at the subarc depth. If the metasomatized rocks in the continental subduction zone would dehydrate to generate fluids with variable geochemical compositions due to multistage fluid-rock interactions, the fluids could further infiltrate the surrounding rock and possibly the mantle wedge to result in further geochemical transfer from the subducting slab to the mantle wedge.
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Petrological and zircon evidence for anatexis of UHP Quartzite during continental collision in the Sulu orogen
Journal of Metamorphic Geology, 2013Co-Authors: Yi-xiang Chen, Yong-fei ZhengAbstract:Petrological evidence is provided for anatexis of ultrahigh-pressure (UHP) metamorphic Quartzite in the Sulu orogen. Some feldspar grains exhibit elongated, highly cuspate shapes or occur as interstitial, cuspate phases constituting interconnected networks along grain boundaries. Elongated veinlets composed of plagioclase + quartz ± K-feldspar also occur in grain boundaries. These features provide compelling evidence for anatexis of the UHP Quartzite. Zircon grains from impure Quartzite are all metamorphic growth with highly irregular shape. They contain inclusions of coesite, jadeite, rutile and lower pressure minerals, including multiphase solid inclusions that are composed of two or more phases of muscovite, quartz, K-feldspar and plagioclase. All zircon grains exhibit steep REE patterns, similar U–Pb ages and Hf isotope compositions with a weighted mean of 218 ± 2 Ma. Most grains have similar δ18O values of −0.6 to 0.1‰, but a few fall in the range −5.2 to −4.3‰. Thus, these grains would have grown from anatectic melts at various pressures. Zircon O isotope differences indicate that anatectic melts were derived from different sources with contrasting O isotopes, but similar Hf isotopes, that is, one from the Quartzite itself and the other probably from the country-rock granitic gneiss. Zircon grains from pure Quartzite contain relict magmatic cores and significant metamorphic overgrowths. Domains that contain eclogite facies minerals exhibit flat HREE patterns, no Eu anomalies and concordant U–Pb ages of c. 220 Ma. Similar U–Pb ages are also obtained for domains that contain lower pressure minerals and exhibit steep REE patterns and marked negative Eu anomalies. These observations indicate that zircon records subsolidus overgrowth at eclogite facies conditions but suprasolidus growth at lower pressures. Zircon enclosed by garnet gave consistent U–Pb ages of c. 214 Ma. Such garnet is interpreted as a peritectic product of the anatectic reaction that involves felsic minerals and possibly amphibole and titanite. The REE patterns of epidote and titanite also record multistage growth and metasomatism by anatectic melts. Therefore, the anatexis of UHP metamorphic rocks is evident during continental collision in the Triassic.
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.