Molybdenite Re-Os isotopic age of the Kunshan Mo-W-Cu polymetallic deposit in the Jiangxi Province and its evolution of metallogenic geodynamics

This paper is the result of mineral exploration engineering.

Objective Kunshan molybdenum polymetallic deposit is located in Xiushui County, Jiangxi Province, and belongs to eastern segment of the Jiuling uplift from mid-segment of the Jiangnan orogen. This study attempts to precisely constrain the metallogenic age of the Kunshan W-Cu-Mo polymetallic deposit, provide geochronological evidence for the study of mineralization and the summary of the metallogenic regularity of the deposit, study the metallogenic relationship of the deposit and the source of metallogenic material, and divide the metallogenic periods of the Dahutang tungsten polymetallic ore concentration area.

Methods The Re-Os isotopic geochronology for the molybdenite from the Kunshan molybdenum polymetallic deposit was carried out in this paper.

Results An isochron age of (148.8±1.0) Ma, and a weighted mean age of (148.7±0.7) Ma for 10 molybdenite samples were obtained, which were approximately simultaneous with each other, and the Re-Os system was closed accordingly. The points of ¹⁸⁷Re and ¹⁸⁷Os are far away along the isochron, which indicates that the geochronology data are reliable. Metallogenesis lags behind the emplacement of porphyritic-like biotitic granite in the Kunshan deposit, caused by Late Jurassic granitic magmatism. Metallogenic materials of the Kunshan molybdenum polymetallic deposit mainly came from crust materials, in addition, there are two samples with higher Re, it shows that partial mantle source metallogenic materials participated in the formation of the deposit.

Conclusions The intrusion of asthenospheric materials began from the Late Jurassic epoch, through the intersection part of NNE deep faults and NEE ancient faults formed from Late Jinningian. Partial melting of crustal material was caused by the heat conduction effect, which forms a series of intermediate-acid intrusive rocks in the Dahutang area, such as porphyritic-like biotitic granite, fine-grained biotitic granite, and granite-porphyry.