The Four Plutonic Belts of the Transhimalaya-Himalaya: a Chemical, Mineralogical, Isotopic, and Chronological Synthesis along a Tibet-Nepal Section   总被引：31，自引：0，他引：31  

DEBON  FRANCOIS; FORT  PATRICK LE; SHEPPARD  SIMON M. F.; SONET  JACQUES 《Journal of Petrology》1986,27(1):219-250

The geochemistry (major, trace element, O- and Sr-isotope ratios)and petrology of the Transhimalaya, North Himalaya, High Himalayaand ‘Lesser Himalaya’ plutonic belts are comparedbased on the analyses of up to 492 samples. The composite Transhimalaya batholith is subalkaline or monzoniticin character rather than calc-alkaline. Its genesis was probablyclosely related to subduction processes associated with strike-slipmovement. It was emplaced on both sides of the boundary betweenan earlier metavolcanic arc and a continental margin. Two principalperiods of magmatic activity occurred: Upper Cretaceous and,particularly in this region, Eocene at the time of the India-Eurasiacollision when sediments may have become involved in the subductionprocess. Magmatic differentiation, characterized by two superimposedstages of evolution, and hybridization processes, involvingboth basic and acidic magmas, can account for the genesis ofthe different plutonic units. Although a continental contributionis implied, the isotopic data (6.8 < ¹⁸O < 9?2; 0?704< ⁸⁷Sr/⁸⁶Sr, < 0?707) preclude a significant contributionfrom either old crust or surface derived sediments. The North, High and ‘Lesser’ Himalaya plutonic beltsare fundamentally different and correspond to aluminous associationsof two groups of ages (Lower Palaeozoic for the ‘LesserHimalaya’ and part of the North Himalaya; Upper Cenozoicfor the High Himalaya and part of the North Himalaya). Theyare all high-¹⁸O (9 < ¹⁸O < 14) granites and adamelliteswith high initial ⁸⁷Sr/⁸⁶Sr, ratios (0?709 to < 0?740). TheLower Palaeozoic group was generated within the Gondwana continentalcrust, independent of any true orogenesis, with a probable butlimited contribution from the mantle. High Himalaya and NorthHimalaya Cenozoic plutons are directly linked to the activityof the Main Central Thrust. They were derived by similar anatecticprocesses of the same continental source rocks. The small butdistinct chemical and mineralogical differences among the plutonsare related to the increase in the intensity of anatexis ongoing towards the north and the east.  相似文献