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Zircon U-Pb ages and Hf isotopic composition of the Pu Sam Cap high-potassic alkaline rocks in northwestern Vietnam and regional tectonic implication

Tran M.D. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China|
Tang Y. | Ji M. | Chen Y. | Nguyen Q.L. | Liu J.L. Hanoi University of Mining and Geology, Hanoi, Viet Nam|

Acta Petrologica Sinica Số 6, năm 2010 (Tập 26, trang 1902-1914)

ISSN: 10000569

ISSN: 10000569

DOI:

Tài liệu thuộc danh mục: Scopus

Article

English

Từ khóa: Geochronology; Granite; Hafnium; Igneous rocks; Isotopes; Lead; Rocks; Sedimentology; Silicate minerals; Tectonics; Titanium; Trace elements; Zircon; Alkaline rocks; Hf isotope; Mantle source; Red River Shear Zone; Viet Nam; Zircon U-Pb age; Sedimentary rocks; alkaline rock; emplacement; granite; hafnium; isotopic composition; lamprophyre; magmatism; mantle source; potassic rock; shear zone; shoshonite; subduction; syenite; tectonic setting; trace element; trachyte; uranium-lead dating; zircon; Ailao Mountains; China; Indochina; Red River [Asia]; Viet Nam; Yunnan
Tóm tắt tiếng anh
The Pu Sam Cap high-potassic alkaline rocks are located in western part of the southern segment of Ailao Shan-Red River shear zone, including high-potassic alkaline trachyte, lamprophyre, syenite and alkaline granite. There into, the trachyte lays unconformably upon the Upper Cretaceous sedimentary rocks. The syenite and alkaline granite intruded the Triassic terrigenous sedimentary rocks, Jurassic rhyolite and amphibole-bearing granitic intrusion of 40 ∼ 35Ma. The Pu Sam Cap potassic alkaline rocks are geochemically characterized by rdatively low Ti02 (<0. 8%), P205(<0.64%) and FeO* (<7.74%) and high Na2O (1.41% ∼ 4. 5%) and K2O (5. 22%-9. 4%), coupled with high contents of incompatible trace elements. They are ultrapotassic or shoshonitic enriched in LILE, LREE and compatible elements, and have marked Nb, Ta and Ti depletion, which is similar to a subduction related component and has the characteristics of post-collisional arc type potassic igneous rocks. Zircon LA-ICPMS U-Pb dating gives the emplacement age of 32. 70 ±0. 24Ma for high-potassic syenite and 35. 1 ±0. 06Ma for alkaline granite. Their εHf (t) values are-2. 8 ∼2. 5 and-4. 9 ∼ 0. 1 with two-stage Hf model ages of 950 ∼ 1286Ma and 1107 ∼ 1421 Ma, εNd(t) values of-5. 63 ∼-3. 26, high 87Sr/86Sr(0.706254-0.707273) and low 143Nd/144Nd (0.512336-0.512447). It is suggested that the Pu Sam Cap high-potassic alkaline rocks were resulted from mixing between mantle and crust-derived magmas and may be derived from an EM2 mantle. The remnant of the subduction of Yangtze plate beneath the Indochina plate during the closure of the Mojiang Paleotethyan oceanic basin, and the Cenozoic continental collision between Indian and Eurasian plates provide a broad tectonic background for the Pu Sam Cap potassic alkaline magmatism.

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