学术
摘 要:
喜马拉雅超高压变质带主要由表壳岩石组成，其中的长英质变质岩已经全部退变质，只在基性的榴辉岩中保留有某些超高压变质矿物。这些超高压变质矿物在锆石、石榴石及其他一些化学和机械性质稳定的矿物中以微米级的包裹体形式产出。到目前为止，已经在TsoMorari结晶穹隆和上Kaghan谷高喜马拉雅结晶岩中发现了超高压指示矿物柯石英和多晶石英假像。这2个地区同属一个超高压变质带，具有相似的构造背景、岩石组成及变质年龄。Kaghan谷超高压变质岩形成条件为700770℃和2．7—3．2GPa，相当干90-110km的上地幔深度，形成年龄为（46．2±0．7）Ma.TsoMorari结晶穹隆中超高压变质岩的形成条件约为750℃和3．9GPa，形成年龄为（48±1）Ma。上述超高压变质带在其折返过程中普遍经历了强烈的水化和角闪岩相退变质作用。研究表明，印度大陆地壳俯冲的垂向速率为1．1～1．4cm／a，水平速率为4．5cm／a，俯冲到约100km深度时的平均俯冲角度为14～19°。[著者文摘]
文章出处:
《地质科技情报》-2006年25卷4期 -69-73页
栏目信息:
分 类 号:
文献标识码:
A
文章编号:
1000-7849（2006）04-0069-05
Ultra-high Pressure Metamorphism of Himalaya
ZHANG Jin-feng,ZHANG Ze-ming （Institute of Geology, CAGS,Beijing 100037,China）
Abstract:
The Himalayan orogen is an ultra-high pressure （UHP） metamorphic belt is mainly composed of supracrustal rocks. The quartzofeldspathic units are thoroughly back reacted, and only mafic eclogite lenses and boudins retain scattered in UHP phases. These UHP minerals are restricted to micro-scale inclusions in chemically and mechanically resistant zircon, garnet, and a few other strong container minerals. So far, UHP crystallize index minerals such as coesite and coesite pseudomorphs have been discovered in Tso-Morari crystalline dome and Kaghan Valley. They belong to a single UHP belt with similar tectonic setting, lithologies, and UHP metamorphic ages. The Kaghan Valley is estimated to have formed at about 700- 770℃ and 2.7-3.2 GPa,equivalent to 90-110 km in mantle depth, and （46.2±0.7） Ma. The Tso-Morari crystalline dome was subjected to UHP metamorphism about at 750 ℃, 3.9 GPa, and （48-1-1） Ma. These units mentioned above were subsequently exhumed to crustal depths and subjected to intense hydration and amphibolite-facies overprint. It is found that the average vertical sinking rate and horizontal velocity are respectively 1.1-1.4 cm/a and 4.5 cm/a,and the average subduction angle is 14-19° at 100 km depth.[著者文摘]
Key words:
Himalaya ; ultra-high pressure metamorphism;continental collision
基金资助:
国家重点基础研究发展规划（973）项目（2003CB7166501）;国家自然科学基金重大项目（40399142;40472036）
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