Plutonic rocks of the 1985 Tibet Geotraverse, Lhasa to Golmud
Plutonic rocks of the 1985 Tibet Geotraverse, Lhasa to Golmud
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DOI：
10.1098/rsta.1988.0124
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发表时间：
1988-12
期刊：
影响因子：
--
通讯作者：
N. Harris;Xu Ronghua;C. Lewis;Jin Chengwei
中科院分区：
文献类型：
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作者：
N. Harris;Xu Ronghua;C. Lewis;Jin Chengwei
西藏中部高原上露出两块向东的大型花岗岩浴岩。在拉萨地体南部，藏布缝合带以北，冈底斯带为钙碱性复式岩基，以二长闪长岩、英云闪长岩、花岗闪长岩和二长花岗岩为主。微量元素表明，强烈分馏熔体侵位于活动大陆边缘；地壳更深层次的岩基暴露在地壳起源的念青唐格拉正麻岩中。在高原北缘，一套由英云闪长岩、花岗闪长岩和二长花岗岩组成的同构造钙碱性岩套形成了昆仑岩基，南侧为构造后花岗岩。昆仑侵入体来自活动大陆边缘或最近活动大陆边缘上方地壳中深熔的含石榴石源区。在这两块熔岩之间，拉萨地体北部出露了一套变铝质英云闪长岩-花岗闪长岩和过铝质二云母花岗岩的双峰式岩石，指示了上地壳熔融和地壳或上地幔更深层次的熔融。这种关联暗示了碰撞后的设置。
Two large east-trending granitic batholiths are exposed on the plateau of Central Tibet. In the southern Lhasa Terrane , north of the Zangbo Suture, the Gangdise Belt is a calc-alkaline composite batholith dominated by monzodiorites, tonalites, granodiorites and monzo granites. Trace elements indicate that strongly fractionated melts were emplaced at an active continental margin; deeper crustal levels of the batholith are exposed in the crustally -derived Nyainqentanglha orthogneiss. A long the northern edge o f the plateau , a syn-tectonic calcic to calc-alkaline suite of tonalites, granodiorites and monzo granites forms the Kunlun batholith with post-tectonic granites emplaced to the south. The Kunlun intrusions are derived from anatexis of a garnet-bearing source at in termediate crustal depths above an active or recently active continental margin . Between these two batholiths, a bimodal suite of metaluminous tonalite -grano-diorite and peraluminous two-mica granite is exposed in the northern Lhasa Terrane, indicative of melting both in the upper crust and at deeper levels in the crust or upper mantle. This association suggests a post-collision setting.