LA-ICP-MS Analysis of Minerals from the Shizhuyuan W-Polymetallic Deposit, South China: Implications for Mineralization of Pb, W, Mo and Bi

Abstract

The South China Block (SCB) is a globally important metallogenic district containing numerous W-Sn deposits. Extensive studies of W-polymetallic deposits in this region have greatly improved our understanding of the petrogenesis, geochronology and metallogenesis of these systems. However, studies on the mobilization of ore-forming elements between mineralization- and alteration-related minerals using in situ analyses are rare. Using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), we analyzed W, Pb, Mo and Bi concentrations in silicate minerals and scheelite from granites and skarns associated with the Shizhuyuan W-polymetallic deposit in the Nanling Range in the SCB. Data show that muscovitized biotite in granites contains high W contents. Pb mainly occurs in K-feldspar and plagioclase in granites and epidote and scheelite in skarns. Bi mainly occurs in epidote in skarns. Scheelite in skarns contains high W and Mo contents. Pb isomorphously substitutes K or Ca in silicate minerals and scheelite. W isomorphously substitutes Ti in biotite. Mo isomorphously substitutes W in scheelite and occurs as W-bearing submicroscopic inclusions in minerals with low contents. Bi isomorphously substitutes Pb when the Pb content is relatively high and occurs as Bi-bearing micro or submicroscopic inclusions in minerals when the Pb content is low. Biotite and feldspar are altered in a magmatic-hydrothermal process, W enriched in biotite, Pb enriched in feldspar and the W-, Pb-, Mo- and Bi-bearing submicroscopic inclusions are excluded from minerals and released to the magmatic-hydrothermal fluids. Large amounts of W are precipitated in scheelite when the fluids come in contact with carbonate rocks to form skarn, while a few contents of Pb, Mo and Bi are distributed in skarn minerals. Thus, large amounts of Pb, Mo, Bi and residual W remain in the fluids, which results in the formation of a W-Sn-Mo-Bi massive skarn ore.