东波地幔橄榄岩是雅鲁藏布江缝合带内代表性超镁铁岩体,位于缝合带西段,面积超过400km2。为查明岩体成因,在岩体中实施了一口千米深的科学钻探(DSD-1)。除上部有约23m厚的第四系堆积物外,钻孔均钻进在地幔橄榄岩中,孔深1002.06m,岩心采...东波地幔橄榄岩是雅鲁藏布江缝合带内代表性超镁铁岩体,位于缝合带西段,面积超过400km2。为查明岩体成因,在岩体中实施了一口千米深的科学钻探(DSD-1)。除上部有约23m厚的第四系堆积物外,钻孔均钻进在地幔橄榄岩中,孔深1002.06m,岩心采取率96.62%。岩心编录结合显微镜下鉴定将岩心划分出44个岩性单元层,并进一步归并为上、下两套岩性:上部(23.1~340.17m)为含单辉方辉橄榄岩(斜方辉石含量为15~20%,单斜辉石含量不足5%);下部(340.17~1002.06m)为方辉橄榄岩(斜方辉石含量为10%~15%,几乎不含单斜辉石),其中发育薄层状纯橄岩和辉石岩以及辉绿岩脉。矿物学及全岩地球化学研究揭示:①东波地幔橄榄岩以方辉橄榄岩为主,其次为含单辉方辉橄榄岩,它们均具有亏损的全岩地球化学及矿物成分组成,指示它们为经历过中高程度部分熔融后的地幔残余岩石;经历过富水流体(熔体)交代作用,表现为角闪石呈柱状交代斜方辉石;②纯橄岩和辉石岩以透镜状或薄层状脉体发育于方辉橄榄岩中,具有岩浆成因的矿物组成,见交代矿物角闪石,指示它们可能为交代成因;③辉绿岩脉兼具N-MORB和弧玄武岩的化学属性,以低SiO2、高MgO和高Al2O3含量为特征,具有与Western Lau Basin玄武岩一致的REE配分型式,形成于较为成熟的弧后盆地环境。东波地幔橄榄岩(及其中的纯橄岩、辉石岩和辉绿岩脉)在成因上与俯冲带关系密切,都受到了与俯冲带相关地质作用的影响。展开更多
Objective The Guangshigou uranium deposit is located in the eastern part of the Shangdan triangular domain, which is currently the most productive pegmatite-hosted uranium deposit in China. Previous studies have focus...Objective The Guangshigou uranium deposit is located in the eastern part of the Shangdan triangular domain, which is currently the most productive pegmatite-hosted uranium deposit in China. Previous studies have focused on the migration and precipitation of uraninite and biotite clusters in the uraniferous pegmatites(Li Yanhe et al., 2016; Yuan et al., 2018). However, the accurate uranium mineralization age still remains poorly constrained, thus展开更多
Voluminous platinum-group mineral （PGM） inclusions including erlichmanite （Os,Ru）S2, laurite （Ru,Os）S2, and irarsite （Ir, Os,Ru,Rh）AsS, as well as native osmium Os（Ir） and inclusions of base metal sulphides ...Voluminous platinum-group mineral （PGM） inclusions including erlichmanite （Os,Ru）S2, laurite （Ru,Os）S2, and irarsite （Ir, Os,Ru,Rh）AsS, as well as native osmium Os（Ir） and inclusions of base metal sulphides （BMS）, including millerite （NiS）, heazlewoodite （NiaS2）, covellite （CuS） and digenite （Cu3S2）, accompanied by native iron, have been identified in chromitites of the Zedang ophiolite, Tibet. The PGMs occur as both inclusions in magnesiochromite grains and as small interstitial granules between them; most are less than 10 ~m in size and vary in shape from euhedral to anhedral. They occur either as single or composite （biphase or polyphase） grains composed solely of PGM, or PGM associated with silicate grains. Os-, Ir-, and Ru-rich PGMs are the common species and Pt-, Pd-, and Rh-rich varieties have not been identified. Sulfur fugacity and temperature appear to be the main factors that controlled the PGE mineralogy during crystallization of the host chromitite in the upper mantle. If the activity of chalcogenides （such as S, and As） is low, PGE clusters will remain suspended in the silicate melt until they can coalesce to form alloys. Under appropriate conditions of fS2 and fO2, PGE alloys might react with the melt to form sulfides-sulfarsenides. Thus, we suggest that the Os, Ir and Ru metallic clusters and alloys in the Zedang chromitites crystallized first under high temperature and low fS2, followed by crystallization of sulphides of the laurite-erlichmanite, solid-solution series as the magma cooled and fS2 increased. The abundance of primary BMS in the chromitites suggests that fS2 reached relatively high values during the final stages of magnesiochromite crystallization. The diversity of the PGE minerals, in combination with differences in the petrological characteristics of the magnesiochromites, suggest different degrees of partial melting, perhaps at different depths in the mantle. The estimated parental magma composition suggests formation in a suprasubduction zone environment, perhaps in a forearc.展开更多
The Dangqiong ophiolite, the largest in the western segment of the Yarlung-Zangbo Suture Zone(YZSZ)ophiolite belt in southern Tibet, consists of discontinuous mantle peridotite and intrusive mafic rocks. The former is...The Dangqiong ophiolite, the largest in the western segment of the Yarlung-Zangbo Suture Zone(YZSZ)ophiolite belt in southern Tibet, consists of discontinuous mantle peridotite and intrusive mafic rocks. The former is composed dominantly of harzburgite, with minor dunite, locally lherzolite and some dunite containing lenses and veins of chromitite. The latter, mafic dykes(gabbro and diabase dykes), occur mainly in the southern part. This study carried out geochemical analysis on both rocks. The results show that the mantle peridotite has Fo values in olivine from 89.92 to 91.63 and is characterized by low aluminum contents(1.5–4.66 wt%) and high Mg# values(91.06–94.53) of clinopyroxene. Most spinels in the Dangqiong peridotites have typical Mg# values ranging from 61.07 to 72.52, with corresponding Cr# values ranging from 17.67 to 31.66, and have TiO2 contents from 0 to 0.09%, indicating only a low degree of partial melting(10–15%). The olivine-spinel equilibrium and spinel chemistry of the Dangqiong peridotites suggest that they originated deeper mantle(>20 kbar). The gabbro dykes show N-MORB-type patterns of REE and trace elements. The presence of amphibole in the Dangqiong gabbro suggests the late-stage alteration of subduction-derived fluids. All the lherzolites and harzburgites in Dangqiong have similar distribution patterns of REE and trace elements, the mineral chemistry in the harzburgites and lherzolites indicates compositions similar to those of abyssal and forearc peridotites, suggesting that the ophiolite in Dangqiong formed in a MOR environment and then was modified by late-stage melts and fluids in a suprasubduction zone(SSZ) setting. This formation process is consistent with that of the Luobusa ophiolite in the eastern Yarlung-Zangbo Suture Zone and Purang ophiolite in the western Yarlung-Zangbo Suture Zone.展开更多
The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series...The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.展开更多
Resent studies show that a large number of unusual minerals are hosted mainly by chromites in the mantle sections of ophiolites （Bai et al., 2000;Yang et al., 2007; Yang et al., 2015）. These minerals include native ...Resent studies show that a large number of unusual minerals are hosted mainly by chromites in the mantle sections of ophiolites （Bai et al., 2000;Yang et al., 2007; Yang et al., 2015）. These minerals include native elements, oxides, carbides, PGE and base metal alloys, sulphides, silicates and have significant potential petrogenic and geodynamic significance.展开更多
The northeastern Jiangxi Province ophiolite is located in the SE margin of the Yangtze Block, along the Zhangshudun （Yiyang） Xingangshan （Dexing）, ophiolite belt extending northeast for about 100kin （Zhou, 1989; ...The northeastern Jiangxi Province ophiolite is located in the SE margin of the Yangtze Block, along the Zhangshudun （Yiyang） Xingangshan （Dexing）, ophiolite belt extending northeast for about 100kin （Zhou, 1989; Li et al., 1997）. The original sequence of the NE Jiangxi ophiolite suite has been structurally disrupted and enclosed by a strongly foliated flysch sequence. Most of the dismembered peridotites of NEJXO are highly serpentinized, requiring care in applying petrochemistry and geochemistry to distinguish their tectonic setting,展开更多
Platinum-group elements （PGE） are mainly concentrated in some specific minerals known as PGMs, which commonly occur in podifbrm chromites of ophiolites. In-situ PGM assemblages in chromites can provide valuable info...Platinum-group elements （PGE） are mainly concentrated in some specific minerals known as PGMs, which commonly occur in podifbrm chromites of ophiolites. In-situ PGM assemblages in chromites can provide valuable information on the physico-chemical nature of the parental melt（s） from which chromitite crystallized （Melcher et al., 1997）, and used as a significant petrogenetic indicator.展开更多
文摘东波地幔橄榄岩是雅鲁藏布江缝合带内代表性超镁铁岩体,位于缝合带西段,面积超过400km2。为查明岩体成因,在岩体中实施了一口千米深的科学钻探(DSD-1)。除上部有约23m厚的第四系堆积物外,钻孔均钻进在地幔橄榄岩中,孔深1002.06m,岩心采取率96.62%。岩心编录结合显微镜下鉴定将岩心划分出44个岩性单元层,并进一步归并为上、下两套岩性:上部(23.1~340.17m)为含单辉方辉橄榄岩(斜方辉石含量为15~20%,单斜辉石含量不足5%);下部(340.17~1002.06m)为方辉橄榄岩(斜方辉石含量为10%~15%,几乎不含单斜辉石),其中发育薄层状纯橄岩和辉石岩以及辉绿岩脉。矿物学及全岩地球化学研究揭示:①东波地幔橄榄岩以方辉橄榄岩为主,其次为含单辉方辉橄榄岩,它们均具有亏损的全岩地球化学及矿物成分组成,指示它们为经历过中高程度部分熔融后的地幔残余岩石;经历过富水流体(熔体)交代作用,表现为角闪石呈柱状交代斜方辉石;②纯橄岩和辉石岩以透镜状或薄层状脉体发育于方辉橄榄岩中,具有岩浆成因的矿物组成,见交代矿物角闪石,指示它们可能为交代成因;③辉绿岩脉兼具N-MORB和弧玄武岩的化学属性,以低SiO2、高MgO和高Al2O3含量为特征,具有与Western Lau Basin玄武岩一致的REE配分型式,形成于较为成熟的弧后盆地环境。东波地幔橄榄岩(及其中的纯橄岩、辉石岩和辉绿岩脉)在成因上与俯冲带关系密切,都受到了与俯冲带相关地质作用的影响。
基金provided by the Bureau of Geology of the Chinese National Nuclear Corporation (grants No. 2016YFE0206300, (2018)294, 3210402 and LTC1605-1)
文摘Objective The Guangshigou uranium deposit is located in the eastern part of the Shangdan triangular domain, which is currently the most productive pegmatite-hosted uranium deposit in China. Previous studies have focused on the migration and precipitation of uraninite and biotite clusters in the uraniferous pegmatites(Li Yanhe et al., 2016; Yuan et al., 2018). However, the accurate uranium mineralization age still remains poorly constrained, thus
基金financially supported by the National Natural Science Foundation of China (Grant No.41262002,40930313,41302052,41502062)National Industry Special Projects (Sino Probe-05-02)+2 种基金China Bureau of Geological Survey Projects (DD20160023-01)IGCP-649Institute of Geology, Chinese Academy of Geological Science (J1526)
文摘Voluminous platinum-group mineral （PGM） inclusions including erlichmanite （Os,Ru）S2, laurite （Ru,Os）S2, and irarsite （Ir, Os,Ru,Rh）AsS, as well as native osmium Os（Ir） and inclusions of base metal sulphides （BMS）, including millerite （NiS）, heazlewoodite （NiaS2）, covellite （CuS） and digenite （Cu3S2）, accompanied by native iron, have been identified in chromitites of the Zedang ophiolite, Tibet. The PGMs occur as both inclusions in magnesiochromite grains and as small interstitial granules between them; most are less than 10 ~m in size and vary in shape from euhedral to anhedral. They occur either as single or composite （biphase or polyphase） grains composed solely of PGM, or PGM associated with silicate grains. Os-, Ir-, and Ru-rich PGMs are the common species and Pt-, Pd-, and Rh-rich varieties have not been identified. Sulfur fugacity and temperature appear to be the main factors that controlled the PGE mineralogy during crystallization of the host chromitite in the upper mantle. If the activity of chalcogenides （such as S, and As） is low, PGE clusters will remain suspended in the silicate melt until they can coalesce to form alloys. Under appropriate conditions of fS2 and fO2, PGE alloys might react with the melt to form sulfides-sulfarsenides. Thus, we suggest that the Os, Ir and Ru metallic clusters and alloys in the Zedang chromitites crystallized first under high temperature and low fS2, followed by crystallization of sulphides of the laurite-erlichmanite, solid-solution series as the magma cooled and fS2 increased. The abundance of primary BMS in the chromitites suggests that fS2 reached relatively high values during the final stages of magnesiochromite crystallization. The diversity of the PGE minerals, in combination with differences in the petrological characteristics of the magnesiochromites, suggest different degrees of partial melting, perhaps at different depths in the mantle. The estimated parental magma composition suggests formation in a suprasubduction zone environment, perhaps in a forearc.
基金funded by grants from the NSF China (No. 41672046, 41720104009)the China Geological Survey (DD20160023-01)+1 种基金the Ministry of Science and Technology (201511022)IGCP (International Geoscience Programme) Project 649
文摘The Dangqiong ophiolite, the largest in the western segment of the Yarlung-Zangbo Suture Zone(YZSZ)ophiolite belt in southern Tibet, consists of discontinuous mantle peridotite and intrusive mafic rocks. The former is composed dominantly of harzburgite, with minor dunite, locally lherzolite and some dunite containing lenses and veins of chromitite. The latter, mafic dykes(gabbro and diabase dykes), occur mainly in the southern part. This study carried out geochemical analysis on both rocks. The results show that the mantle peridotite has Fo values in olivine from 89.92 to 91.63 and is characterized by low aluminum contents(1.5–4.66 wt%) and high Mg# values(91.06–94.53) of clinopyroxene. Most spinels in the Dangqiong peridotites have typical Mg# values ranging from 61.07 to 72.52, with corresponding Cr# values ranging from 17.67 to 31.66, and have TiO2 contents from 0 to 0.09%, indicating only a low degree of partial melting(10–15%). The olivine-spinel equilibrium and spinel chemistry of the Dangqiong peridotites suggest that they originated deeper mantle(>20 kbar). The gabbro dykes show N-MORB-type patterns of REE and trace elements. The presence of amphibole in the Dangqiong gabbro suggests the late-stage alteration of subduction-derived fluids. All the lherzolites and harzburgites in Dangqiong have similar distribution patterns of REE and trace elements, the mineral chemistry in the harzburgites and lherzolites indicates compositions similar to those of abyssal and forearc peridotites, suggesting that the ophiolite in Dangqiong formed in a MOR environment and then was modified by late-stage melts and fluids in a suprasubduction zone(SSZ) setting. This formation process is consistent with that of the Luobusa ophiolite in the eastern Yarlung-Zangbo Suture Zone and Purang ophiolite in the western Yarlung-Zangbo Suture Zone.
基金supported by the State Key Laboratory Foundation Project(No.GPMR0508) from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences
文摘The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.
基金financially supported by the National Natural Science Foundation of China (40930313, 41262002)the Ministry of Science and Technology of China (2014DFR21270)+1 种基金China Geological Survey (12120115026801, 12120115027201, 201511022)the Fund from the State Key Laboratory of Continental Tectonics and Dynamics (Z1301-a20)
文摘Resent studies show that a large number of unusual minerals are hosted mainly by chromites in the mantle sections of ophiolites （Bai et al., 2000;Yang et al., 2007; Yang et al., 2015）. These minerals include native elements, oxides, carbides, PGE and base metal alloys, sulphides, silicates and have significant potential petrogenic and geodynamic significance.
基金financially supported by the National Natural Science Foundation of China(No.41262002)the Key Laboratory of Radioactive Geology and Exploration Technology Fundamental Science for National Defense (No. 2012RGET06)
文摘The northeastern Jiangxi Province ophiolite is located in the SE margin of the Yangtze Block, along the Zhangshudun （Yiyang） Xingangshan （Dexing）, ophiolite belt extending northeast for about 100kin （Zhou, 1989; Li et al., 1997）. The original sequence of the NE Jiangxi ophiolite suite has been structurally disrupted and enclosed by a strongly foliated flysch sequence. Most of the dismembered peridotites of NEJXO are highly serpentinized, requiring care in applying petrochemistry and geochemistry to distinguish their tectonic setting,
基金financially supported by the National Natural Science Foundation of China (40930313, 41262002)National Industry Special Projects (Sino Probe-05-02)China Bureau of Geological Survey Projects (12120115027201, 1212011121263)
文摘Platinum-group elements （PGE） are mainly concentrated in some specific minerals known as PGMs, which commonly occur in podifbrm chromites of ophiolites. In-situ PGM assemblages in chromites can provide valuable information on the physico-chemical nature of the parental melt（s） from which chromitite crystallized （Melcher et al., 1997）, and used as a significant petrogenetic indicator.
