A discussion on the genetic model of the copper deposit in Lala copper orefied, Sichuan Province

The tectonic environment of the Lala copper orefield is located in the Sichuan-Yunnan passive continental margin rift system of Huili County, Sichuan Province, and its mineralization is controlled by the tectonic-magmatic evolution of the Huili-Dongchuan rift trough.The orebody is located in the Na-rich spilite-keratophyre series of the Paleoproterozoic Hekou Group.The values of the δ³⁴S of metal sulfide in the ore are distributed in the range of -1‰~4‰, and are close to zero, which have characteristics of tower distribution, indicating that sulfur mainly came from volcanic eruption.The fluid type of the deposit is similar to that of the volcanic effusive sedimentary deposit, the inclusions are basically Ⅰ-type inclusions in early quartz sulfide and Ⅱ-type and Ⅲ-type inclusions in late calcite quartz sulfide; I-type inclusions reflect the main metallogenic stage of volcanic eruptive-sedimentary period, while Ⅱ-type and Partial Ⅲ-type inclusions reflect terminal fluid miscibility, which indicates that the deposit has undergone late reformation.According to isotopic dating data, the metallogenic process of the deposit can be roughly divided into three stages:volcanic spouting(1600~1800 Ma), metamorphism and deformation(1000~1100 Ma), and hydrothermal superposition modification(770~900 Ma).It is preliminarily considered that the genetic type of deposits about the Lala copper orefield belongs to marine volcanic rock type copper deposit, but different volcanic eruption cycles of Estuary Group have different mineralization patterns.