Journal - Himalayan and Transhimalayan granitic rocks in and adjacent to Nepal and their mineral potential

Himalayan and Transhimalayan granitic rocks in and adjacent to Nepal and their mineral potential

A. H. G. Mitchell

HMG/UNDP Mineral Exploration Project, Lainchaur, Kathmandu, Nepal

Jour. Nep. Geol. Soc., Vol. 1, Number 1, 1981, 41-52


Abstract

Granitic rocks occupying eight distinct tectonic settings can be recognized in the Himalayas and Transhimalayas. In the Lower Himalayas geographical belt a few plutons of two-mica granite intrude the lowest unit of the Nawakot Complex or Midland Group. More extensive are sheet-like bodies of augen gneiss intrusive within a possibly thrust-bounded succession of carbonates and graphitic schists beneath the Main Central Thrust to the north. The most abundant granites in the Lower Himalayas are the two-mica cordierite-bearing granites within klippen; minor tin and tungsten mineralization is associated with these plutons, which are of late Cambrian age. Within the Higher Himalayas above the Main Central Thrust, the `Central Crystallines' or Central Gneisses include pegmatites and pegmatitic granites intrusive into gneisses of probable early Proterozoic age; these have same potential for ruby, sapphire, aquamarine and possibly spodumene. Further north within the Higher Himalayan succession a southern belt of anatectic two-mica granites and leucogranites of mid-Tertiary age is favourable for tin, tungsten and uranium mineralization; a northern belt of granites or gneisses is of uncertain age and origin. North of the Indus Suture in the Transhimalayas extensive batholiths of hornblende granodiorite representing the root zone of a late Mesozoic to early Eocene volcanic arc are associated with porphyry copper deposits. Further north in southern Tibet the tectonic setting for reported granitic bodies of Tertiary age is uncertain; their location suggests that they could be favourable host rocks for tin, uranium and porphyry molybdenum mineralization.

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