Alteration and mineralization zoning, ore textures and ore-forming process of Yongping copper deposit, Jiangxi Province

Abstract

Yongping copper deposit, associated with S-W-Pb-Zn mineralization, is located at the southern margin of the Jiangshan-Shaoxing suture and between the Yanshanian granite belt and the Hercynian-Indosinian depression in the northern Wuyi Mountains. Late Paleozoic stratigraphy, Yanshanian granite, and copper ore body is controlled by thrust napper structure, as the basement rocks of the Zhoutan Group thrusting on the Late Paleozoic strata, Early Yanshanian biotite granite-granodiorite, quartz porphyry, and granite porphyry intruding along weak planes of thrust, and stratiform ore bodies occurring within the skarnized Carboniferous Yejiawan Formation. The ore body occurred in garnet skarn, phyllitic shale and skarnized marble. This study deciphers the ore-forming episodes and metallogenic process of the deposit based on mineralization-alteration zonation and textures of the ores. Exploration and mining working faces indicate that the mineralization and alteration of the deposit is granite-centered. If taking one side into consideration, i. e., from the granite to the limestone wall rock, following zonation can be delineated : (1) skarn minerals vary from garnet, via diopside, to wollastonite ; (2) the garnet varies in color from red, via brown, to green; (3) economic mineralization mainly occurring as banded and stock veins in the brown garnet skarn zone, leading to the ore grade increasing firstly and then decreasing. Metal mineral association of banded and stock veins in skarns, metasandstone-shales, and large sulfide-quartz veins ( up to 10m wide) is identical, consisting mainly of pyrite, scheelite, galena, sphalerite and chalcopyrite, indicating that different types of ores in the Yongping copper deposit are products of the same hydrothermal mineralization system in diverse wall rocks and ore-controlling structures. According to mineral assemblages and ore textures, six metallogenic stages can be divided for the deposit, which are garnet, mag-hematite, scheelite, iron-copper sulfide, lead-zinc sulfide, and carbonate stages, respectively. Skarn zonation formed during garnet stage, and massive pyrrhotite-grunerite formed at late period of this stage; magnetite, hematite composed mag-hematite stage; scheelite stage dominate tungsten mineralization, occurring as quartz-scheelite stock and disseminated wolframite. Iron-copper sulfide stage is the main period of copper mineralization; lead-zinc and carbonate stage likely marks the late and end of the primary mineralization, respectively.