Mineralization Age and Petrogenesis of Associated Intrusions in the Mingze-Chengba Porphyry-Skarn Mo-Cu Deposit, Gangdese
详细信息
- 责任者：Sun Xiang (State Key Laboratory of Geological Processes and Mineral Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Zheng Youye
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(4)
- 关键词：钼矿 ; molybdenum ores ; 铜矿 ; copper ores ; 冈底斯山 ; Gangdise Range
- 页码：p.1392-1406
- 图表：illus., 4 tables, 63 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Kelu-Chongmuda metallogenic belt, different from the Gangdese Miocene porphyry-skarn Cu-Mo-Au belt, is characterized by Oligecene porphyry-skarn Mo-W-Cu mineralization. The types and petrogenesis of intrusions associated with Oligecene mineralization and the reason for the difference between the Kelu-Chongmuda and Gangdese mineralization remain topics of debate, which prevents the evaluation of resource potentiality. Therefore, we conducted the geochronological analysis and research on the petrogenesis of associated intrusions for the Chengba porphyry Mo deposit and Mingze skarn Cu deposit. The Mingze monzonlite associated with skarn mineralization has zircon SHRIMIP U-Pb age of 30.4±0.6Ma, indicating that the Mingze mineralization took place at ca. 30Ma, which is consistent with the mineralization age of the Chengba porphyry Mo deposit. The Mingze monzonlite are shoshonitie, with low SiO2 (55%～57%), high K2O (2.7%～5.0%), MgO (3.5%～6.9%), Mg# value (57.6～67.2), high abundances of compatible elements (e.g., Cr=34×10-6～379×10-6; Ni=48×10-6～116×10-6), and low Sr/Y ratios (24～49). The Chengba granodiorite, with the zircon SHRIMIP U-Pb age of 28.7±0.9Ma, are high-K calc-alkaline, with high SiO2 (65%～67%), high K2O (3.2%～4.1%), MgO (1.7%～2.1%), Mg# value (49.5～51.1), low abundances of compatible elements (e.g., Cr=20×10-6～39×10-6; Ni=16×10-6～25×10-6), and low Sr/Y ratios (53～76). Both the monzonlite and granodiorite display enriched LREE and LILE, depleted HSFE, marked negative Nb-Ta-Ti anomalies, and slightly negative Eu anomalies. However, the monzonlite have high abundances of REE than the granodiorite. They also have similar Hf isotopic compositions with εHf(t)=+2.8～+6.8 for the monzonlite and εHf(t)=+4.2～+6.1 for the granodiorite. Our new data, together with previously published work, lead us to suggest that the parental magmas of the Mingze monzonlite were most likely derived from enriched lithospheric mantle beneath southern Tibet and the Chengba granodiorites were derived from partial melting of a thickened juvenile lower crust. The magma mixing between the crust-derived and mantle-derived magmas is beneficial for the porphyry-skarn Cu-Mo mineralization in the Kelu-Chongmuda and Gangdese metallogenic belts. But due to the more intensive erosion in the Kelu-Chongmuda than in the Gangdese, the upper Cu bodies were not preserved and the lower Mo bodies were present in the Chengba porphyry Mo deposit.
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