Formation Age and Geochemical Characteristics of Supahe Granite Pluton in Longling Area, Yunnan Province: Magmatic Response to Pan-African Movement

Acid magmatic events are the important basis used by geologists to delineate the area of Gondwanal and also an important manifestation of Pan-African movement in qinghai-tibet plateau. The Supahe Granite,southeast side of Longling-Ruili fault (referred to as Longrui fault), developed in Longling Area, Yunnan Province, is one of the acid plutons,mainly composed of granodiorite and monzogranite.The main pluton is of massive structure and weak gneissic structure with a series of NE trending narrow ductile deformation zones.LA-ICP-MS zircon U-Pb dating of 6 undeformed granite samples shows that the emplacement age of Supahe Granite is 527-519 Ma, being an acidic intrusion of the 2^nd stage of Cambrian Newfoundland.The major and rare elements from 23 fresh undeformed samples show that Supahe granite is characterized by high silicon, alkali and aluminum.It belongs to S-type peraluminous granite with high-K, calc alkaline series.The total REE content is relatively high, with ΣREE=34.69×10^-6~348.20×10^-6, and the difference of light and weight rare earth elements is obvious, L/H=2.04~33.31, (La/Yb)_N=1.31~67.65. It has the strong negative Eu anomaly with δEu=0.1~0.9. The trace elements are enriched in ion lithophile elements such as Rb, Ba, K and other LILE elements of Th, Ta, Ce, Hf, etc. It is obviously depleted in Sr, Eu, Ti, etc.The composition of major and rare elements shows that the magma has undergone fractional crystallization and differentiation of plagioclase.The isotopic characteristics of ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd indicated that the Supahe granite was originated in the partial melting of the late-Proterozoic crust, with some mantle material mixed in it. The discriminant diagram of tectonic environment showed that the Supahe granite formed in the collision tectonic environment, being the result of the closure and collision of Pan-African ocean in the Pan-African movement.