The spinel peridotite xenoliths of Group I in Quaternary basanites from Nushan, Anhui Province, can be classified as two suites: 8 hydrous suite characterized by the ubiquitous oc-currence of (Ti-) pargasite and an an...The spinel peridotite xenoliths of Group I in Quaternary basanites from Nushan, Anhui Province, can be classified as two suites: 8 hydrous suite characterized by the ubiquitous oc-currence of (Ti-) pargasite and an anhydrous suite. The mineral chemistry reveals that the an-hydrous suite and one associated phlogopite-bearing lherzolite are equilibrated under temperatureconditi0ns of 1000 - 1110℃, whereas amphibole-bearing peridotites display distinct disequilibrium features, indicating partial reequilibration from 1050 to 850℃ and locally down to 750℃.This amphibole-bearing peridotites were probably the uppermost part of the high temperatureanhydrous suite which was modally modified by fractionating H2O-rich metasomatic agent during regional upwelling. This relatively recent lithospheric uplift event foll0wed an older upliftevent recognized from pyroxene unmixing of domains in local equilibrium, as well as the dominant deformation texture in the anhydrous suite. The first thermal disturbance can be linkedwith the regional extension and widespread basaltic volcanism in Jiangsu-Anhui provinces sinceEarly Tertiary and the formation of the nearby Subei (North Jiangsu) fault-depression basinduring the Eocene, while the second event in association with the formation of amphibolesprobably indicates the continuation but diminution of upward mantle flux since Neogene in response to the change in tectonic regime for eastern China.展开更多
On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous R...On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous Region, we have found, either on a microscopic or on a macroscopical scale and in different positions of the sections, the most direct and most important mineralogical and micro\|textural evidence for the development of metasomatism in the process of weathering\|pedogenesis of numerous carbonate rocks. This paper also has expounded for the first time and systematically the mechanism of metasomatism involved in the process of weathering\|pedogenesis of carbonate rocks and proposed the sequence of mineral metasomatic evolution in the process of weathering\|pedogenesis of carbonate rocks.展开更多
A group of εNd-La/Nb, Ba/Nb, Nb/Th diagrams are used to study mantleheterogeneity. Island-arc basalts (IAB) are distributed in a triangle of these diagrams.Three end-member components (the MORB-type depleted mantle, ...A group of εNd-La/Nb, Ba/Nb, Nb/Th diagrams are used to study mantleheterogeneity. Island-arc basalts (IAB) are distributed in a triangle of these diagrams.Three end-member components (the MORB-type depleted mantle, the fiuid released fromsubducted oceanic crust and the sediments from the continental crust) of the source ofIAB may be displayed in these diagrams. Two types of IAB are identified. They areof the two-component type (with little continental sediments), such as the basalts fromAleutians and New Britain, and the three-component type, such as those from Sunda,Lesser Antilles and Andes. In addition, the EMII type mantle-derived rocks may alsobe divided into two groups. One is exemplifled by continental flood basalts and someperidotite xenoliths, similar to IAB, with high La/Nb and Ba/Nb and low Nb/Th ratios.The other includes the Samoa-type oceanic island basalts, with low La/Nb and Ba/Nband high Nb/Th ratios. The corresponding two sub-components of EMII are EMIIM,which is related to the metasomatism of lithosphere mantle by fluids released from thesubducted oceanic crust, and EMIISR, related to the intervention of recycling continentalsediments into the convective mantle.展开更多
Phlogopite-amphibole-pyroxenite xenoliths contained in the alkali basic-ultrabasic subvolcanic complex in Langao, Shaanxi Province, are composed of diopside, Ti-rich pargasite, phlogopite apatite, sphene and ilmenite,...Phlogopite-amphibole-pyroxenite xenoliths contained in the alkali basic-ultrabasic subvolcanic complex in Langao, Shaanxi Province, are composed of diopside, Ti-rich pargasite, phlogopite apatite, sphene and ilmenite, which have subsolidus metamorp hism- de formation textures such as triple-points, cataclastic boundaries and kink-bands. Mineral chemical characteristics show that the diopside, Ti-rich pargasite and phlogoPite are derived from the mantle and are the products of mantle metasomatism. Compared with normal mantle-derivedspinel-lherzolites, the xenoliths are enriched in TiO2, Fe2O3, CaO, Na2O and K2O, with apparent depletion in MgO. Chondrite-normalized REE patterns and primordial-mantle normalized trace elements data show that they are enriched in REE (especially LREE) and incompatible trace elements. The petrographic, mineralogical and petrochemical characteristics indicate that the xenoliths are metasomatized mantle xenoliths, which offers the evidence for mantle metasomatism and represents the anomalous mantle beneath the Early Paleozoic rift in northern Daba Mountains. The agents of mantle metasomatism are probably derived from the rising of mantle hot plumes. The processes of metasomatism varied from limited-range fluid metasomatism in deep mantle (＞90 km) to pervasive metasomatism of silicate melt.展开更多
文摘The spinel peridotite xenoliths of Group I in Quaternary basanites from Nushan, Anhui Province, can be classified as two suites: 8 hydrous suite characterized by the ubiquitous oc-currence of (Ti-) pargasite and an anhydrous suite. The mineral chemistry reveals that the an-hydrous suite and one associated phlogopite-bearing lherzolite are equilibrated under temperatureconditi0ns of 1000 - 1110℃, whereas amphibole-bearing peridotites display distinct disequilibrium features, indicating partial reequilibration from 1050 to 850℃ and locally down to 750℃.This amphibole-bearing peridotites were probably the uppermost part of the high temperatureanhydrous suite which was modally modified by fractionating H2O-rich metasomatic agent during regional upwelling. This relatively recent lithospheric uplift event foll0wed an older upliftevent recognized from pyroxene unmixing of domains in local equilibrium, as well as the dominant deformation texture in the anhydrous suite. The first thermal disturbance can be linkedwith the regional extension and widespread basaltic volcanism in Jiangsu-Anhui provinces sinceEarly Tertiary and the formation of the nearby Subei (North Jiangsu) fault-depression basinduring the Eocene, while the second event in association with the formation of amphibolesprobably indicates the continuation but diminution of upward mantle flux since Neogene in response to the change in tectonic regime for eastern China.
基金This research project was financially supported by both National Natural Science Foundation of China (GrantNo .4 980 0 0 3)andCross Century Qualified Personnel Program of Guizhou Province
文摘On the basis of mineralogical, geochemical and micro\|textural studies of the typical sections of the red weathering crust of carbonate rocks in the subtropical karst areas of Guizhou Province and Guangxi Autonomous Region, we have found, either on a microscopic or on a macroscopical scale and in different positions of the sections, the most direct and most important mineralogical and micro\|textural evidence for the development of metasomatism in the process of weathering\|pedogenesis of numerous carbonate rocks. This paper also has expounded for the first time and systematically the mechanism of metasomatism involved in the process of weathering\|pedogenesis of carbonate rocks and proposed the sequence of mineral metasomatic evolution in the process of weathering\|pedogenesis of carbonate rocks.
文摘A group of εNd-La/Nb, Ba/Nb, Nb/Th diagrams are used to study mantleheterogeneity. Island-arc basalts (IAB) are distributed in a triangle of these diagrams.Three end-member components (the MORB-type depleted mantle, the fiuid released fromsubducted oceanic crust and the sediments from the continental crust) of the source ofIAB may be displayed in these diagrams. Two types of IAB are identified. They areof the two-component type (with little continental sediments), such as the basalts fromAleutians and New Britain, and the three-component type, such as those from Sunda,Lesser Antilles and Andes. In addition, the EMII type mantle-derived rocks may alsobe divided into two groups. One is exemplifled by continental flood basalts and someperidotite xenoliths, similar to IAB, with high La/Nb and Ba/Nb and low Nb/Th ratios.The other includes the Samoa-type oceanic island basalts, with low La/Nb and Ba/Nband high Nb/Th ratios. The corresponding two sub-components of EMII are EMIIM,which is related to the metasomatism of lithosphere mantle by fluids released from thesubducted oceanic crust, and EMIISR, related to the intervention of recycling continentalsediments into the convective mantle.
文摘Phlogopite-amphibole-pyroxenite xenoliths contained in the alkali basic-ultrabasic subvolcanic complex in Langao, Shaanxi Province, are composed of diopside, Ti-rich pargasite, phlogopite apatite, sphene and ilmenite, which have subsolidus metamorp hism- de formation textures such as triple-points, cataclastic boundaries and kink-bands. Mineral chemical characteristics show that the diopside, Ti-rich pargasite and phlogoPite are derived from the mantle and are the products of mantle metasomatism. Compared with normal mantle-derivedspinel-lherzolites, the xenoliths are enriched in TiO2, Fe2O3, CaO, Na2O and K2O, with apparent depletion in MgO. Chondrite-normalized REE patterns and primordial-mantle normalized trace elements data show that they are enriched in REE (especially LREE) and incompatible trace elements. The petrographic, mineralogical and petrochemical characteristics indicate that the xenoliths are metasomatized mantle xenoliths, which offers the evidence for mantle metasomatism and represents the anomalous mantle beneath the Early Paleozoic rift in northern Daba Mountains. The agents of mantle metasomatism are probably derived from the rising of mantle hot plumes. The processes of metasomatism varied from limited-range fluid metasomatism in deep mantle (＞90 km) to pervasive metasomatism of silicate melt.
