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.
Highlights
The South China Block (SCB), with most of the deposits formed during the Mesozoic era, has been recognized as one of the most important W-Sn metallogenic districts in the world [1]
We present in situ LA-ICP-MS element concentration data of major silicate minerals and scheelite in granites and skarns from the Shizhuyuan W-polymetallic deposit
W occurs as an isomorphous substitution and mainly correlates with Ti in biotite
Summary
The South China Block (SCB), with most of the deposits formed during the Mesozoic era, has been recognized as one of the most important W-Sn metallogenic districts in the world [1] It was formed by the amalgamation of the Yangtze Block and Cathaysia Block during the Neoproterozoic era (Figure 1a) and hosts numerous W-Sn deposits, which are mostly concentrated in the Nanling Range located in the central part of the SCB [2,3,4]. We have previously discussed the distribution and mobilization of Sn in the Shizhuyuan W-polymetallic deposit [13], studies on other trace element occurrences in minerals and mobilization between minerals and their alteration products are still insufficient and could improve and deepen the understanding of W mineralization of giant ore accumulations
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