• journal_title：Geological Magazine
• Contributor：QING-DONG ZENG ; JIN-HUI YANG ; JIAN-MING LIU ; SHAO-XIONG CHU ; XIAO-XIA DUAN ; ZUO-LUN ZHANG ; WEI-QING ZHANG ; SONG ZHANG
• Publisher：Cambridge University Press
• Date：2012-09-01
• Format：text/html
• Language：en
• Identifier：10.1017/S0016756811000987
• journal_abbrev：Geological Magazine
• issn：0016-7568
• volume：149
• issue：5
• firstpage：753
• section：Original Articles

The Chehugou granite-hosted molybdenum deposit is typical of the Xilamulun metallogenic belt, which is an important Mo–Ag–Pb–Zn producer in China. A combination of major and trace element, Sr and Nd isotope, and zircon U–Pb isotopic data are reported for the Chehugou batholith to constrain its petrogenesis and Mo mineralization. The zircon SIMS U–Pb dating yields mean ages of 384.7 ± 4.0 Ma and 373.1 ± 5.9 Ma for monzogranite and syenogranite and 265.6 ± 3.5 Ma and 245.1 ± 4.4 Ma for syenogranite porphyry and granite porphyry, respectively. The Devonian granites are calc-alkaline with K₂O/Na₂O ratios of 0.44–0.52, the Permian granites are alkali-calcic with K₂O/Na₂O ratios of 1.13–1.25, and the Triassic granites are calc-alkaline and alkali-calcic rocks with K₂O/Na₂O ratios of 0.78–1.63. They are all enriched in large-ion lithophile elements (LILEs) and depleted in high-field-strength elements (HFSEs) with negative Nb and Ta anomalies in primitive mantle-normalized trace element diagrams. They have relatively high Sr (189–1256 ppm) and low Y (3.87–5.43 ppm) concentrations. The Devonian granites have relatively high initial Sr isotope ratios of 0.7100–0.7126, negative ɛ_Nd(t) values of −12.3 to −12.4 and ²⁰⁶Pb/²⁰⁴Pb ratios of 16.46–17.50. In contrast, the Permian and Triassic granitoids have relatively low initial ⁸⁷Sr/⁸⁶Sr ratios (0.7048–0.7074), negative ɛ_Nd(t) values of −10.1 to −13.1 and ²⁰⁶Pb/²⁰⁴Pb ratios of 17.23–17.51. These geochemical features suggest that the Devonian, Permian and Triassic Chehugou granitoids were derived from ancient, garnet-bearing crustal rocks related to subduction of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China and Siberian plates.