The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identif...The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identified, details of this tectonic setting and the evolution history during the Late Cretaceous remain unclear. To further constrain these issues, we present zircon LA-ICP-MS U-Pb, Hf isotopic and geochemical data of the Gongbari dacites （of the Sangri Group） which intruded by Paleocene granodiorites from the eastern part of the southern Lhasa Terrane, Tibet. New age data indicate that the dacites were generated at -95.4 Ma, which suggests the Sangri Group volcanism may last to Late Cretaceous. The Gongbari dacites are characterized by high Sr （428-758 ppm） contents, low concentration of heavy rare earth elements and Y （e.g. Yb=0.78-1.14 ppm; Y=8.85-11.4 ppm） with high Sr/Y （41.91-67.59） and La/Yb （22.64-30.64） ratios, similar to those of adakite. The rocks are calc-alkaline, metaluminous, enriched in LILEs, depleted in HFSEs, and have positive tar（t） values （＋7.7 to ＋11.6）. The Gongbari dacites were probably produced by partial melting of young and hot subducted Neo- Tethyan oceanic crust under amphibolite to garnet amphibolite-facies conditions. Though the Gangdese Mountains may have formed before Indo-Asian collision, the southern margin of Lhasa Terrane might not go through obviously crustal thickening during the northward subduction of Neo-Tethyan oceanic lithosphere.展开更多
Listwanite from the Luobusa ophiolite, Tibet, forms a narrow, discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mine...Listwanite from the Luobusa ophiolite, Tibet, forms a narrow, discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. Three alteration zones characterized by distinct mineral components and texture are recognized and, in order of increasing degree of alteration, these are： zonem is rich in serpentine minerals; zonen is rich in talc and carbonates; and zone_Ⅰ is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith, although some oxides show linear correlations with MgO. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zone_Ⅰ and zone_Ⅱ and is up to 0.91 g/t in one sample from zonei. We show that CO_2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains, indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. The compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.展开更多
The Zedong ophiolites in the eastern Yarlung-Zangbo suture zone of Tibet represent a mantle slice of more than 45 km2. This massif consists mainly of mantle peridotites, with lesser gabbros, diabases and volcanic rock...The Zedong ophiolites in the eastern Yarlung-Zangbo suture zone of Tibet represent a mantle slice of more than 45 km2. This massif consists mainly of mantle peridotites, with lesser gabbros, diabases and volcanic rocks. The mantle peridotites are mostly harzburgite, lherzolite; a few dike-like bodies of dunite are also present. Mineral structures show that the peridotites experienced plastic deformation and partial melting. Olivine （Fos9.7-91.2）, orthopyroxene （Enss-92）, clinopyroxene （En4-49Wo47-slFS2-4） and spinel [Mg^#=lOOxMg/（Mg＋Fe）]=49.1-70.7; Cr^#=（100xCr/（Cr＋Al）=18.8-76.5] are the major minerals. The degree of partial melting of mantle peridotites is 10%-40%, indicating that the Zedong mantle peridotites may experience a multi-stage process. The peridotites are characterized by depleted major element compositions and low REE content （0.08-0.62 ppm）. Their ＂spoon-shaped＂ primitivemantle normalized REE patterns with （La/Sm）N being 0.50-6.00 indicate that the Zedong ultramafic rocks belong to depleted residual mantle rocks. The PGE content of Zedong peridotites （18.19-50.74 ppb） is similar with primary mantle with Pd/Ir being 0.54-0.60 and Pt/Pd being 1.09-1.66. The Zedong peridotites have variable, unradiogenic Os isotopic compositions with 187Os/18Os=0.1228 to 0.1282. A corollary to this interpretation is that the convecting upper mantle is heterogeneous in Os isotopes. All data of the Zedong peridotites suggest that they formed originally at a mid-ocean ridge （MOR） and were later modified in supra-subduction zone （SSZ） environment.展开更多
在中枢神经系统中，髓鞘是由少突胶质细胞的突起缠绕神经元轴突所形成的管状节段性结构，其主要成分是70％脂类和30％蛋白质构成的鞘磷脂结构，而有髓神经纤维是大脑白质的重要组成部分。目前，检测髓鞘脂类表达的方法有多种，其中劳克...在中枢神经系统中，髓鞘是由少突胶质细胞的突起缠绕神经元轴突所形成的管状节段性结构，其主要成分是70％脂类和30％蛋白质构成的鞘磷脂结构，而有髓神经纤维是大脑白质的重要组成部分。目前，检测髓鞘脂类表达的方法有多种，其中劳克坚牢蓝（1uxol fast blue，LFB）染色是一种较为常用的髓鞘染色方法.但LFB染色也有不同的复染方法，其染色效果亦有差异。本研究通过对成年鼠和幼鼠2种不同鼠龄阶段的大脑髓鞘LFB染色，比较焦油紫和伊红2种不同复染方法的优缺点，为相关研究提供合适的染色方法。展开更多
The Zedang mafic-ultramafic body crops out in the eastern Yarlung-Zangbo suture zone of Tibet. This massif consists of mantle peridotite, gabbro, diabase and volcanic rocks. The mantle peridotites are mostly harzburgite,
基金funded by grants from the National Natural Science Foundation of China (No.40930313)the China Geological Survey (No.12120114057701,No.12120114061801 and No.12120114061501)
文摘The southern Lhasa Terrane is famous for its huge magmatic belt which records the magmatism during Mesozoic and Cenozoic. Although the Mesozoic continental-margin setting in the southern Lhasa Terrane has been identified, details of this tectonic setting and the evolution history during the Late Cretaceous remain unclear. To further constrain these issues, we present zircon LA-ICP-MS U-Pb, Hf isotopic and geochemical data of the Gongbari dacites （of the Sangri Group） which intruded by Paleocene granodiorites from the eastern part of the southern Lhasa Terrane, Tibet. New age data indicate that the dacites were generated at -95.4 Ma, which suggests the Sangri Group volcanism may last to Late Cretaceous. The Gongbari dacites are characterized by high Sr （428-758 ppm） contents, low concentration of heavy rare earth elements and Y （e.g. Yb=0.78-1.14 ppm; Y=8.85-11.4 ppm） with high Sr/Y （41.91-67.59） and La/Yb （22.64-30.64） ratios, similar to those of adakite. The rocks are calc-alkaline, metaluminous, enriched in LILEs, depleted in HFSEs, and have positive tar（t） values （＋7.7 to ＋11.6）. The Gongbari dacites were probably produced by partial melting of young and hot subducted Neo- Tethyan oceanic crust under amphibolite to garnet amphibolite-facies conditions. Though the Gangdese Mountains may have formed before Indo-Asian collision, the southern margin of Lhasa Terrane might not go through obviously crustal thickening during the northward subduction of Neo-Tethyan oceanic lithosphere.
基金funded by National Natural Science Foundation of China (Grant No.40930313)the China Geological Survey (Grants No.12120114061801+1 种基金 No.12120114057701 and No.12120114061501)
文摘Listwanite from the Luobusa ophiolite, Tibet, forms a narrow, discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. Three alteration zones characterized by distinct mineral components and texture are recognized and, in order of increasing degree of alteration, these are： zonem is rich in serpentine minerals; zonen is rich in talc and carbonates; and zone_Ⅰ is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith, although some oxides show linear correlations with MgO. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zone_Ⅰ and zone_Ⅱ and is up to 0.91 g/t in one sample from zonei. We show that CO_2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains, indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. The compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.
基金supported by the Project IGCP–649the China Geological Survey(No.DD20160023–01)
文摘The Zedong ophiolites in the eastern Yarlung-Zangbo suture zone of Tibet represent a mantle slice of more than 45 km2. This massif consists mainly of mantle peridotites, with lesser gabbros, diabases and volcanic rocks. The mantle peridotites are mostly harzburgite, lherzolite; a few dike-like bodies of dunite are also present. Mineral structures show that the peridotites experienced plastic deformation and partial melting. Olivine （Fos9.7-91.2）, orthopyroxene （Enss-92）, clinopyroxene （En4-49Wo47-slFS2-4） and spinel [Mg^#=lOOxMg/（Mg＋Fe）]=49.1-70.7; Cr^#=（100xCr/（Cr＋Al）=18.8-76.5] are the major minerals. The degree of partial melting of mantle peridotites is 10%-40%, indicating that the Zedong mantle peridotites may experience a multi-stage process. The peridotites are characterized by depleted major element compositions and low REE content （0.08-0.62 ppm）. Their ＂spoon-shaped＂ primitivemantle normalized REE patterns with （La/Sm）N being 0.50-6.00 indicate that the Zedong ultramafic rocks belong to depleted residual mantle rocks. The PGE content of Zedong peridotites （18.19-50.74 ppb） is similar with primary mantle with Pd/Ir being 0.54-0.60 and Pt/Pd being 1.09-1.66. The Zedong peridotites have variable, unradiogenic Os isotopic compositions with 187Os/18Os=0.1228 to 0.1282. A corollary to this interpretation is that the convecting upper mantle is heterogeneous in Os isotopes. All data of the Zedong peridotites suggest that they formed originally at a mid-ocean ridge （MOR） and were later modified in supra-subduction zone （SSZ） environment.
文摘在中枢神经系统中，髓鞘是由少突胶质细胞的突起缠绕神经元轴突所形成的管状节段性结构，其主要成分是70％脂类和30％蛋白质构成的鞘磷脂结构，而有髓神经纤维是大脑白质的重要组成部分。目前，检测髓鞘脂类表达的方法有多种，其中劳克坚牢蓝（1uxol fast blue，LFB）染色是一种较为常用的髓鞘染色方法.但LFB染色也有不同的复染方法，其染色效果亦有差异。本研究通过对成年鼠和幼鼠2种不同鼠龄阶段的大脑髓鞘LFB染色，比较焦油紫和伊红2种不同复染方法的优缺点，为相关研究提供合适的染色方法。
文摘The Zedang mafic-ultramafic body crops out in the eastern Yarlung-Zangbo suture zone of Tibet. This massif consists of mantle peridotite, gabbro, diabase and volcanic rocks. The mantle peridotites are mostly harzburgite,
