Petrogenesis of the Late-Carboniferous Granites of Dalaimiao, Inner Mongolia and Its Implications for the Tectonic Transformation of Northern Margin of Xing'an-Mongolian Orogenic Belt
Yang Zeli
Wang Shuqing
Hu Xiaojia
Xin Houtian
Li Chengdong
Abstract：The Dalaimiao pluton crops out in the northern of Suzuoqi, near the border areas between China and Mongolia, which is referred as an important component of the Erenhot-East Ujimqin Late Paleozoic arc magmatic belt and its petrogenesis can provide insights into the tectonic evolution of the northern margins of Xingan-Mongolian orogenic belt.Based on field investigation, geochronology and geochemistry, it is found that the pluton lithologically consists of medium-fine grained biotite granites in the center and medium-grained granites on the margin.Zircon U-Pb dating yields a weighted mean age of 301.2±2.1Ma (MSWD=1.2, 2σ) , indicating these granites were generated during a Late Carboniferous magmatic event.All of these granites are highly siliceous, Fe-poor, slightly peraluminous, and show enrichments in Rb, Th, U, Pb and depletions in Ba, Sr, P, Nb and Ta.The medium-fine grained biotite granites are Na-rich, and have high concentrations of heavy rare earth elements (REE) , whereas the medium-grained granites show higher K2O contents, more significant elemental differentiation and negative europium anomalies.Dalaimiao pluton shows depleted isotopic compositions with (87 Sr/86 Sr) i=0.703 6-0.707 5, εNd (t) =0.08-2.77, and positiveεHf (t) values of 4.70-11.50.Integrated geochronology and geochemical data suggest the Dalaimiao pluton is genetically classified as I-type granites, with some geochemical features of A-type granites.The Dalaimiao granites derived from partial melting of juvenile crust which were generated by the underplating of mantle material, and were formed in a tectonic transitional stage from compression uplift to intracontinental extension.Emplacement of Dalaimiao pluton provides more detailed constraints on the specific timing of tectonic variation in the northern margins of Xingan-Mongolian orogenic belt during the Late Carboniferous.
Keywords：granitesLate PaleozoicXing-Meng orogenic beltpetrogenesistransformation of tectonic settinggeochemistry
Publication Date：2019-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：16( 268-283 )