Abstract:

The age of tungsten mineralization and petrogenesis of its metallogenetic granitoids, and tectonic environment of the Jiulongnao tungsten orefield in southern Jiangxi Province are studied based on the field investigations and analysis on major-, trace-, and rare earth elements and dating. The Jiulongnao granite is characterized by high silica, alkali, metaluminous to weakly peraluminous, low Ca, Mg, and K₂O/Na₂O>1. It also has relatively high LILE (Rb, K), but low LILE (Ba, Sr), and high HFSE (Th, U, Ce, Y, Sm, Nd, Ta, Hf), low HFSE (Nb, P). In addition, Jiulongnao granite shows strong negative Eu anomalies (δEu=0.07-0.10) and high ratios of 10 000Ga/Al (2.76-2.93). Geochemical features of Jiulongnao granite indicate that it belongs to the A-type. The SHRIMP U-Pb dating of zircon from Jiulongnao granite yields an age of (155.8±1.2) Ma. Re-Os isotopic dating of molybdenite from the Hongshuizhai greisentype tungsten deposit by ICP-MS yields a weighted mean age of (156.3±1.3) Ma, which is consistent with diagenetic age of Jiulongnao granite. Combined with chronological data of Chongyi-Dayu-Shangyou tungsten-tin polymetallic ore concentration area, we conclude that the age of both diagenesis and mineralization of this area are mainly concentrated in 150 to 160 Ma, which is corresponding to the time of the second regional large-scale mineralization in the Mesozoic and these mineralization occurred at the same geodynamic background that is Jurassic intraplate extensional environment during the large-scale extension period of lithosphere.

Key words: greisen-type tungsten deposits, SHRIMP U-Pb dating of zircon, Re-Os isotopic dating, isotopes, Jiulongnao granite, Hongshuizhai, southern Jiangxi Province