共查询到18条相似文献，搜索用时 93 毫秒
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通过对采自河北汉诺坝玄武岩中的下地壳和上地幔包体的详细研究 ,建立了本区下地壳—上地幔地温线。该地温线高于大洋地温线和古老地盾地温线 ,接近克拉通边缘的地温线 ,符合该区的大地构造环境。由该地温线建立的下地壳—上地幔地质结构剖面表明 ,该区下地壳主要由不同类型的麻粒岩相岩石组成 ,其化学成分以镁铁质为主 ,深度范围为 2 5～ 4 2km。上地幔由超镁铁质的二辉橄榄岩组成 ,在尖晶石二辉橄榄岩和石榴石二辉橄榄岩之间有一过渡层。由地温线确定的壳幔边界位于 4 2km附近 ,与地震资料确定的莫霍面一致 ,但在壳幔边界之上的下地壳底部有下地壳麻粒岩和超镁铁质岩的互层。这一现象可以解释在下地壳底部常见的层状反射层。该区岩石圈底界大约在 95km ,其下的软流层仍由石榴石二辉橄榄岩组成 相似文献
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岩浆底侵作用与汉诺坝现今壳-幔边界组成 总被引：10，自引：0，他引：10
从汉诺坝新生代玄武岩中岩浆底侵成因的麻粒岩相和榴辉岩相堆晶岩、橄榄岩和辉石岩捕虏体的岩石矿物组合、岩石结构、矿物学、主微量元素和同位素地球化学特征, 讨论和限定了壳-幔边界岩石组成, 并得到岩石高温高压波速实验和深部地球物理探测结果的支持. 现今下部下地壳主要由麻粒岩相镁铁质堆晶岩(以斜长二辉岩为主)组成; 壳-幔过渡带主要由榴辉岩相石榴辉石岩、辉石岩和尖晶石二辉橄榄岩等组成; 太古代地体麻粒岩只是名义上的早期下地壳. 发生在壳-幔边界的岩浆底侵作用导致地壳的垂向增生和壳-幔过渡带的形成, 是显生宙以来壳-幔边界组成和化学调整的重要机制. 相似文献
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岩浆底侵作用与汉诺坝现今壳-幔边界组成--捕虏体岩石学与地球化学证据 总被引：2，自引：0，他引：2
从汉诺坝新生代玄武岩中岩浆底侵成因的麻粒岩相和榴辉岩相堆晶岩、橄榄岩和辉石岩捕虏体的岩石矿物组合、岩石结构、矿物学、主微量元素和同位素地球化学特征, 讨论和限定了壳-幔边界岩石组成, 并得到岩石高温高压波速实验和深部地球物理探测结果的支持. 现今下部下地壳主要由麻粒岩相镁铁质堆晶岩(以斜长二辉岩为主)组成; 壳-幔过渡带主要由榴辉岩相石榴辉石岩、辉石岩和尖晶石二辉橄榄岩等组成; 太古代地体麻粒岩只是名义上的早期下地壳. 发生在壳-幔边界的岩浆底侵作用导致地壳的垂向增生和壳-幔过渡带的形成, 是显生宙以来壳-幔边界组成和化学调整的重要机制. 相似文献
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上地幔尖晶石-石榴石相转变实验研究及其意义 总被引：3，自引：0，他引：3
采用新生代玄武岩中地幔岩捕掳体的矿物、岩石天然样品进行尖晶石与石榴石的相转变实验研究,结果发现尖晶石二辉橄榄岩与石榴石二辉橄榄岩相转变条件(T=1100℃和P=1.8～2.0GPa)与中国东部五相共存的尖晶石/石榴石二辉橄榄岩P-T平衡条件一致.提出中国东部大陆上地幔55～70km深处存在几公里至十几公里厚的尖晶石二辉橄榄岩与石榴石二辉橄榄岩相转变带.尖晶石辉石岩向石榴石辉石岩相转变深度小于55km.实验结果还揭示水促使地幔交代作用,但又抑制了相转变.同时讨论了矿物成分分带现象. 相似文献
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莫霍面是地壳和上地幔的边界,但莫霍面并不是一个简单的"面",而是一个反映地壳和地幔物质交换、相互作用等动力学意义的"过渡带".本文综合深地震反射、宽角地震折射和高温高压岩石物理实验结果,确定壳-幔过渡带的地震P波速度变化范围为6.8~7.5 km·s-1.在克拉通等构造活动稳定地区壳-幔过渡带内的速度梯度强且壳-幔过渡带厚度薄,而在造山带等构造活动区域壳-幔过渡带内的速度梯度弱且壳-幔过渡带厚.中国东部地区的壳-幔过渡带的平均厚度约为5~10 km,在四川盆地下方最薄（<5 km）,而在华北克拉通中部造山带下方的壳-幔过渡带最厚（~30 km）.综合地球化学结果,华北中部巨厚壳-幔过渡带主要是幔源岩浆的底侵作用和堆晶作用而形成. 相似文献
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Using secondary spinel standard method, we have measured precisely the compositions of spinels of amphibole-bearing mantle peridotite xenoliths from Nüshan in eastern China, and calculated the mantle oxygen fugacities recorded by the xenoliths. Results indicate that the mantle metasomatism for forming amphiboles in Nüshan region of Anhui has resulted in the decrease of mantle redox, which is in contrast with theoretical estimation and previous research results from other areas around the world. Combining with related studies on the mantle of eastern China, we give a reasonable explanation to the 'new finding' and further elucidate the compositions and nature of mantle fluids in eastern China. 相似文献
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Jin-Hai Yu Suzanne Y. O&#x;Reilly W. L. Griffin Xisheng Xu Ming Zhang Xinmin Zhou 《Journal of Volcanology and Geothermal Research》2003,122(3-4):165-189
Two localities on the Leizhou Peninsula, southern China (Yingfengling and Tianyang basaltic volcanoes) yield a wide variety of mantle-derived xenoliths including Cr-diopside series mantle wall rocks and two distinct types of Al-augite series pyroxenites. Metapyroxenites have re-equilibrated granoblastic microstructures whereas pyroxenites with igneous microstructures have not thermally equilibrated to the mantle conditions. An abundant suite of megacrysts and megacrystic aggregates (including garnet, plagioclase, clinopyroxene, ilmenite and apatite) is interpreted as the pegmatitic equivalents of the igneous pyroxenite suite. Layered spinel lherzolite/spinel websterite xenoliths were formed by metamorphic differentiation caused by mantle deformation, inferred to be related to lithospheric thinning. Some metapyroxenites have garnet websterite assemblages that allow calculation of their mantle equilibration temperatures and pressures and the construction of the first xenolith geotherm for the southernmost China lithosphere. Heat flow data measured at the surface in this region yield model conductive geotherms (using average crustal conductivity values) that are consistent with the xenolith geotherm for the mantle. The calculated mean surface heat flux is 110 mW/m2. This high heat flux and the high geotherm are consistent with young lithospheric thinning in southern China, and with recent tomography results showing shallow low-velocity zones in this region. The xenolith geotherm allows the construction of a lithospheric rock type section for the Leizhou region; it shows that the crust–mantle boundary lies at about 30 km, consistent with seismic data, and that the lithosphere–asthenosphere boundary lies at about 100 km. 相似文献
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Using secondary spinel standard method, we have measured precisely the compositions of spinels of amphibole-bearing mantle
peridotite xenoliths from Nüshan in eastern China, and calculated the mantle oxygen fugacities recorded by the xenoliths.
Results indicate that the mantle metasomatism for forming amphiboles in Nüshan region of Anhui has resulted in the decrease
of mantle redox, which is in contrast with theoretical estimation and previous research results from other areas around the
world. Combining with related studies on the mantle of eastern China, we give a reasonable explanation to the ‘new finding’
and further elucidate the compositions and nature of mantle fluids in eastern China. 相似文献
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The paleogeotherm derived from spinel and garnet lherzolites xenoliths for the upper mantle beneath Zhejiang Province, China
is higher than the oceanic geotherm but is similar to the geotherm for the upper mantle beneath eastern China constructed
by Xu et al. and the upper mantle geotherm of southeastern Australia. The crust-mantle boundary defined by this geotherm is
about 34 km, while the lithosphere-asthenosphere boundary is about 75 km. This result coincides well with geophysical data.
The study of rheological features of the xenoliths has revealed that at least two periods of deformation events occurred in
the upper mantle beneath this region. The first event might be related to upper mantle diapir occurring in this region before
or during late Tertiary, and the second might be related to the occurrence of small-scale shear zones in the upper mantle.
Project supported by the National Natural Science Foundation of China (Grant No. 49472105). 相似文献
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Abstract The mantle-derived xenoliths entrained in the Pliocene basanite from Baengnyeong Island, South Korea, are spinel lherzolites and spinel harzburgites. The overall compositional range of the Baengnyeong xenoliths matches that of the post-Archean xenoliths of lithospheric mantle origin from eastern China, but without any compositional evidence for a refractory Archean mantle root. Mineral compositions of the xenoliths have been used to estimate the equilibrium temperatures and pressures, and to construct a paleogeothermal gradient of the source region. The xenolith-derived paleogeotherm is constrained from about 820°C at 7.3 kbar to 1000°C at 20.6 kbar. Like those from the post-Archean Chinese xenoliths of lithospheric mantle origin, the Baengnyeong geotherm is considerably elevated relative to the conductive models at the depth of the crust–mantle boundary, reflecting a thermal perturbation probably related to lithospheric thinning. There is no significant P / T difference between harzburgite and lherzolite, which suggests that the harzburgites are interlayered with lherzolites within the depth interval beneath Baengnyeong Island. 相似文献
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