TAILIEUCHUNG - Magma source feature and eruption age of volcanic rocks in the Tram Tau district, Tu Le Basin

This highly enriched magma was postulated to have formed by mixing of a depleted mantle and Mesoproterozoic crustal rocks (for example, granite) following a continental extension event. Mixing between crustal rocks having strontium isotopic ratios of and and a depleted mantle with 87Sr/86Sr ratio of would occur, respectively, at 3÷4% and 2÷5% to generate the observed strontium isotopic ratios in the Tram Tau volcanic rocks. | Vietnam Journal of Earth Sciences 38(3), 242-255 Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Magma source feature and eruption age of volcanic rocks in the Tram Tau district, Tu Le Basin Nguyen Hoang1*, Tran Thi Huong1, Dao Thai Bac2, Nguyen Van Vu2, Nguyen Thi Thu1, Cu Sy Thang1, Pham Thanh Dang1 1 Institute of Geological Sciences, Vietnam Academy of Science and Technology Center of Information and Archives of Geology, General Department of Geology and Minerals of Vietnam 2 Received 19 September 2015. Accepted 13 May 2016 ABSTRACT A set of samples including porphyritic rhyolite, rhyo-trachyte, trachyte and basalt was collected in the Tram Tau district, Tu Le Mesozoic Basin, in NW Viet Nam for analysis for major, trace, elemental and Rb-Sr and Sm-Nd isotopic compositions. The volcanic rocks are alkaline and highly enriched in trace elements including rare earth elements (REEs). However, primitive mantle and chondrite trace element normalized patterns expose strong negative anomalies for Ba, Sr, Eu and Ti, possibly reflecting fractional crystallization of plagioclase (for Sr and Eu), pyroxene, and especially amphibole (for Ba and Ti). The measured 87Sr/86Sr isotopic ratios, varying between and , are plotted against the corresponding 87Rb/86Sr forming an isochron that provides an age of 157± Ma with an initial 87Sr/86Sr ratio of , corresponding to late Jurassic - early Cretaceous (J3-K1) in agreement with previously reported data. The corresponding Nd isotopic compositions expressed as Nd (157Ma) vary from -8,27 to and the Nd model ages are Mesoproterozoic, ranging from 1 to Ga. This highly enriched magma was postulated to have formed by mixing of a depleted mantle and Mesoproterozoic crustal rocks (for example, granite) following a continental extension event. Mixing between crustal rocks having strontium isotopic ratios of and and a depleted

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• Vietnam Journal of Earth Sciences
• Magma source feature
• Eruption age of volcanic rocks
• The Tram Tau district
• Tu Le Basin
• Mesoproterozoic crustal rocks
• The Tram Tau volcanic rocks
• General characteristics of rare earth
• Radioactive elements in Dong Pao deposit
• The natural tap and thermal waters
• Liquid scintillation counter
• Probabilistic seismic hazard assessment for the South Central Vietnam
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• Prediction of maximum earthquake magnitude for northern Vietnam region
• The gev distribution
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• Upper Permian lower Triassic volcanic sequences
• The Hoa Binh area
• northwest Vietnam
• Insignificant cumulative displacement
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• An analysis of forest biomass changes
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