DENG Yi-xiao¹, WANG Zheng-qi^1*, LI Li-rong¹, CAO Da-wang², XIAO Jin-gen², YANG Biao²

(1. Fundamental Science on Radioactive Geology and Exploration Technology Laboratory, East China University of Technology, Nanchang 330013, China;
2. Anhui Nuclear Exploration Technology Centre Institute, Wuhu 241000, China)

Abstract: The K-Ar dating and detailed study on petrogeochemical characteristics of diabase-porphyrite in the Huangmeijian pluton in the Luzong basin were carried out in this paper. The results indicate that the diabase-porphyrite was formed in Late-Cretaceous with an age of 107 Ma. It is characterized with containing two kind of pyroxenes (clinopyroxene and orthopyroxene), SiO2 contents of 51.93%-58.87%, alkaline rich, high K content, poor in Ti, enriched in LREE, LILE, and incompatible elements, no Eu depletion, and has similar REE and trace element distribution patterns to those of the oceanic basalt (OIB). It has (87Sr/86Sr)i values of 0.70575-0.70588, DSr values of 57.46-58.80, (143Nd/144Nd)i values of 0.512124-0.512188, and εNd(t) values varying from -6.1 to -7.3. It is concluded that the diabase-porphyrite in the Huangmeijian area belongs to shoshonite which was originated from enriched mantle (EMI); The formation and evolution of magmatism in the Luzong basin were related to the extensional environment after the continental collision between the Yangzi and North China blocks and the partial melting of the enriched mantle which was caused by the upwelling of asthenospheric materials. As the age of Huangmeijian shoshonite has fundamentally constrained a time limit for the lithospheric thinning in the Luzong area, it is speculated that the dynamic evolution process of the lithospheric thinning could be played an important constraint on the hydrothermal uranium mineralization.

Keywords: Shoshonite; K-Ar dating; petrogeochemistry; the Huangmeijian pluton ; the Luzong basin

ACTA MINERALOGICA SINICA Vol. 39, No.6, 2019, page 617-626