Genesis of S‐type Granites in the Pengshan Sn‐polymetallic Ore Field, Northern Jiangxi Province and its Implications

Abstract

AbstractThe Pengshan Sn‐polymetallic ore field is located in the southeastern part of the Yangtze block, spanning the southeast edge of the MLYDZ and the northern edge of the mid‐segment of the Jiangnan Uplift, and on one side of the MLYDZ. The studies of LA–ICP–MS zircon U–Pb chronology and petrogeochemistry for Early Cretaceous acid granites from the Pengshan ore field were carried out in this paper. We report zircon U–Pb geochronology and whole‐rock geochemistry for acid granites in the Pengshan ore field. The zircon U–Pb ages of the muscovite‐granite, biotite adamellite and granite‐porphyry are 127.6 ± 1.7 Ma, 126.9 ± 1.6 Ma and 126.6 ± 2.0 Ma, respectively. The granites in Pengshan are characterized by a high silicon content and are rich in alkali. They belong to high‐potassium, calc‐alkaline, peraluminous granite. The rocks have a relatively high Rb/Ba ratio, and the data points for muscovite‐granite and biotite adamellite all fall within the clay‐rich sources region, near the pelite‐derived end‐member, showing that the Pengshan muscovite‐granite and biotite adamellite mainly originated from the partial melting of metapelites with high maturity. The transformation of the compressional and extensional tectonics in this region approximately 128 Ma obviously lags behind that in the mid‐segment of the Jiangnan Uplift (135 Ma), but occurred earlier than the MLYDZ (126 Ma). The Pengshan ore field extends from the mid‐segment of the Jiangnan Uplift to the MLYDZ. Although the tectonic stress field is constrained by the combination of the two secondary tectonic units, the time of tectonic system transformation is closer to the MLYDZ because the spatial orientation of the area is enclosed in the MLYDZ. Relevant geophysical and drilling data confirm the rationality of Pengshan–Ao'xia as a multi‐center vertical zoning ore field, and show the scientificity of the prospecting idea of abutting joint between the north‐west of Pengshan area and the south‐east of Ao'xia area.