The Eastern Himalayan syntaxis
There are three main geologic units in the EHS. The Himalayan terrane is composed of the Tethys-Himalayan sequence and the High Himalayan crystalline sequence, and is part of the Indian Plate. The Tethys-Himalayan sequence is mainly composed of low-grade metasedimentary rocks as well as Paleozoic and Mesozoic sediments, while the High Himalayan crystalline sequence is composed of high-grade metamorphic rocks. The Indus-Tsangpo Suture zone is the suture zone created by the convergence of the Indian and Eurasian plates; it is folded around the EHS, and separates the Himalayan terrane from the south Lhasa terrane. The Lhasa terrane is formed of two geologic units: the granulite facies metamorphic unit, which has granulitic lenses or blocks within the amphibolite facies country rock, and the amphibolite facies metamorphic unit, which consists of amphibolite, gneiss, schist, and some marble and quartzite. It also contains a Gangdese batholith chain. The map below (Figure 1) depicts the rock types present in the EHS.
These two terranes came together at the convergence of the Indian and Eurasian plates, which first began to converge approximately 50 million years ago.
The final structure shown on the geologic maps (best shown in Figure 3) is the dextral faulting around the rock of the Himalayan terrane.
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