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青藏高原地壳上地幔形成与演化的地球物理研究 总被引:6,自引:0,他引:6
近年来,我国在青藏高原取得了大量地球物理资料,1980-1982年中法合作又在西藏得到丰富的深部地球物理资料.青藏高原是一个整体.它的构造活动可以分为南、北、中三个带.中部是整体隆升,且已达到均衡.南北两缘受到强烈挤压、叠覆,是差异隆升,但未达到均衡.它的构造作用形式,可以分为上、中、下三层.上层(上地壳)以叠覆为主,中层(下地壳)以挤压为主,下层(异常地幔)以隆升为主.在上下地壳之间有一壳内低速低阻层,是一个主要的滑曳面.它的地质历史发展可以分为两个阶段.印度板块与西藏板块未碰撞前,异常地幔使高原缓慢隆升.在碰撞后,地壳加厚,重力均衡使高原快速隆升. 相似文献
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Mesozoic high-K granitic rocks from the eastern Dabie Mountains, Central China and their geological implications 总被引:9,自引:0,他引:9
The Mesozoic high-K granitic intrusions from the eastern Dabie Mountains, Central China, can be divided into three superunits
namely the Yaohe, Penghe and Huangbai superunits. The Yaohe superunit is compositionally dominated by quartz monzonite extending
as a band in NW direction which is differently foliated, contains numerous dioritic enclaves and has been dated as 174 Ma.
The Penghe superunit, widely distributed in the field, varies in composition but is dominated by quartz monzonitic and granitic
rocks, which is massive in structure, has well developed with dioritic enclaves and is aged in 125-127 Ma. The Huangbai superunit
is mainly composed of granitic composition which is massive in structure, rarely contains dioritic enclaves and is aged in
120-111 Ma. These three superunits of granitic intrusions can also be clearly distinguished in geochemistry. They have recorded
an orogenic process of the Dabie Mountains from the end of regional metamorphism to the overprinting of the circum-Pacific
tectonic regime. 相似文献
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后碰撞幔源岩浆活动、底垫作用及准噶尔盆地基底的性质 总被引:83,自引:2,他引:81
准噶尔盆地周边地区广泛发育晚古生代后碰撞花岗岩类、基性_超基性杂岩和火山岩 .它们普遍具有正的εNd(t)值 ,表明岩浆起源于亏损地幔 ,并不同程度地受到地壳物质的混染 .幔源岩浆及其分异产物在上地壳侵位只是深部地质过程的浅部反映 ,大量的幔源岩浆很可能在壳幔界面附近和下地壳中发生底垫作用 ,成为准噶尔盆地基底的组成部分 .如果准噶尔盆地的基底是残留洋壳 ,除非发生高度部分熔融 ,否则不可能产生基性_超基性杂岩 .即使准噶尔盆地具有老陆壳基底 ,也会因为幔源岩浆底垫作用而受到强烈改造 .这种解释可以与地球物理资料相容 . 相似文献
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