Title: Early Miocene leucogranites in Dinggye area, southern Tibet: Formation mechanism and tectonic implications
Abstract: The Ama Drime Massif, Dinggye area, is located in the central Greater Himalaya and consists of granitic gneisses, metapelites, metabasites and massive leucogranites, and has experienced amphibolite- to granulite-facies metamorphism. Whole-rock major- and trace-element, radiogenic isotope (Sr and Nd), and SHRIMP zircon analyses were undertaken to investigate the petrogenic relationship between the leucogranites and the metamorphic rocks, as well as the formation mechanism of the leucogranites. Bulk element and Sr-Nd isotope analyses show that the leucogranites have (1) high SiO2 (72%), Al2O3 (12%), and A/CNK (1.0); (2) high Rb and low Sr, thus high Rb/Sr ratios (1.0); (3) high contents of total REE, and substantial negative Eu anomalies; and (4) high initial Sr (87Sr/86Sr(t)=0.7621~0.8845) and low Nd (eNd(t)=-13.0~-20.2) isotopic compositions. High Rb/Sr ratios and Sr-Nd isotope systematics indicate that the leucogranites were mainly derived from muscovite dehydration melting of metapelite with a substantial contribution from granitic gneiss. SHRIMP zircon U-Pb dating indicates that the leucogranites have preserved a record of two episodes of partial melting at 21.0±0.7Ma and 15.8±0.1Ma, respectively; and the granitic gneisses experienced high-grade metamorphism at 22.2±1.4Ma, similar to the timing of retrograde metamorphism in this area. In conclusion, both granitic and pelitic gneisses have experienced high-grade metamorphism and anatexis. The Miocene anatectic event could be episodic and at least produced leucogranitic melts at 22~21Ma and ~16Ma, respectively.
Publication Year: 2011
Publication Date: 2011-07-01
Language: en
Type: article
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Cited By Count: 21
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