关键词: 扬子陆核, 古元古代, 圈椅埫花岗岩, A型花岗岩, 构造意义

Abstract:

This study carries out systematical geochemical and geochronological investigations on the Quanyi-shang granitic pluton intruding into the Kongling Complex, and discusses the petrogenesis and Paleoproterozoic evolution of the nucleus of the Yangtze craton. The zircon LA-ICP-MS U-Pb dating shows that crystallization age of the granite is (1 822±44) Ma, hence a typical product of Paleoproterozoic magmatism of the Yangtze continental interior. The geochemical research illustrates a depletion of Al, Mg and enrichment of Rb, Th, as well as negative anomalies of high field strength elements (HFSE) and Eu, Ba and Sr. High Ga/Al ratio and Zr+Nb+Ce+Y content and relatively high calculated zircon saturation temperature (＞862 ℃), combined with other geochemical features, indicate that the Quanyishang granitic pluton is aluminous A-type granite. The εNd(t) value varies between -12.4 to -10.3 and the correspondent two-stage Nd isotopic modal ages range from 3.3 to 3.2 Ga. These characteristics imply that the granite may have formed by partial melting of ancient felsic crustal material in the nucleus of the Yangtze craton under a low-pressure, high-temperature condition at a post-collisional extensional tectonic setting. Combined with the documented work, it may have relationship with the regional tectonic transition from collisional extrusion to extention in a post-collisional setting during the period from 2.0 to 1.9 Ga. The Paleoproterozoic tectonic magmatic events of the Yangtze craton is consistent with the global 2.1-1.8 Ga collisional orogeny to breakup events related to the evolution of Columbia supercontinent, indicating that the nucleus of the Yangtze craton may have been an important part of Columbia supercontinent.

Key words: nucleus of the Yangtze craton, Paleoproterozoic, Quanyishang granite, A-type granite, tectonic implication