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Petrogenesis of Himalayan Leucogranites: Perspective From a Combined Elemental and Fe‐Sr‐Nd Isotope Study
Author(s) -
Shi Qingshang,
He Yongsheng,
Zhao Zhidan,
Liu Dong,
Harris Nigel,
Zhu DiCheng
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2021jb021839
Subject(s) - petrogenesis , anatexis , geology , geochemistry , tourmaline , leucogranite , tectonics , rare earth element , petrology , mineralogy , rare earth , partial melting , mantle (geology) , paleontology , metamorphic rock , gneiss
The petrogenesis of Himalayan leucogranites remains crucial for understanding the thermal and tectonic evolution of the Himalayan orogen. To understand whether they are largely pristine melts of crustal anatexis or have experienced a high degree of fractional crystallization (FC), we present Fe isotopic data of 30 representative Himalayan leucogranites and 9 local metasedimentary rocks. Excepting three garnet leucogranites with low δ 56 Fe (−0.04‰–0.06‰) that are likely affected by garnet accumulation, tourmaline, and two‐mica leucogranites have largely homogeneous δ 56 Fe from 0.13‰ to 0.24‰ irrespective of their highly variable SiO 2 , MgO, and FeOt contents. Combined with observed mineral assemblages and available fractionation factors, this does not support a high degree of FC (with or without assimilation) in their petrogenesis. The elevated δ 56 Fe relative to the supposed source rocks, represented by metasedimentary rocks and/or metabasite with a δ 56 Fe value of 0.10‰, by ∼0.07‰, may reflect Fe isotope fractionation during crustal anatexis. This study indicates most leucogranites can provide robust constraints on the conditions of crustal anatexis and thus the thermal and tectonic evolution of the Himalayan orogen.