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Wenquan |
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Gansu, China |
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Mo
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
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The Triassic Wenquan porphyry Mo deposit is located in Wushan County, Gansu, northwestern China, ~60 km WNW of the city of Tianshui (#Location: 34° 36' 51"N, 105° 5' 59"E).
It lies within the Western Qinling section of the >4000 km long Central China Orogenic Belt that formed during a long-lived series of multiple divergence and convergence events between the North China and Tarim blocks to the north, and South China Block and Tibet in the south. The greater orogenic belt comprises, from west to east, the Kunlun, Qilian, Qinling and Dabie Mountains.
For a more detailed description of the setting see the East Qinling Mo Belt, Qinling-Dabie Mo Belt and West Qinling Gold Province records. Wenquan lies within the area covered by the latter, and on the West Qinling Orogen geological map in that record, lies within the Triassic granitoid to the north of the Liba gold deposit.
As of 2024, Wenquan was the only significant Triassic porphyry Mo deposit in the Western Qinling Orogen.
The deposit is hosted by the 250 km2, composite Wenquan batholith, which is composed of five lithofacies, namely, biotite granite, biotite monzogranite porphyry, porphyritic monzogranite, monzogranite porphyry and porphyritic syenogranite (Han, 2009). This batholith intruded a suite of gently-dipping Palaeo- to Mesoproterozoic Qinling Group strata to the NE, predominantly composed of schist and gneiss, and the Devonian Dacaotan Group, primarily clastic and carbonate rocks, to the SW (Qiu et al., 2014). Three NW-trending mafic bodies intrude the batholith 4 to 8 km to the NE, namely the Lannigou, Yangjiashan-Shijishan and Heigou dykes (Han, 2009). Abundant mafic enclaves have been recognised, mainly within the biotite monzogranite porphyry, porphyritic monzogranite and monzogranite porphyry (Cao et al., 2011; Qiu et al., 2014). These mafic enclaves exhibit a consistent directional alignment, mineral assemblage and geochemical composition to that of the mafic dykes (Han, 2009; Zhu et al., 2011). The host granite porphyries of the Wenquan complex batholith are an intermediate to felsic, and high-K calc-alkaline to shoshonitic suite of peraluminous to metaluminous granites with I-type affinity (Zhu et al., 2011). They have relatively higher MgO contents and Mg# compared to normal crustal-derived felsic magmas, but lower Nb/Ta ratios compared to the mafic enclaves (Cao et al., 2011; Zhu et al., 2011). These intrusions have ben interpreted to have resulted from magma mixing during their Late Triassic emplacement as part of the transition from a collisional setting, between the South Qinling and South China Blocks, to a post-collision rebound setting (Zhu et al., 2011; Chen and Santosh, 2014).
The two prominent phases associated with Mo mineralisation at Wenquan are biotite granite porphyry and monzogranite porphyry. U-Pb dating of zircons from these mineralised granitoids are respectively reported as 223 ±3 Ma and 225 ±3 Ma (Cao et al., 2011), 218 ±2.4 Ma and 221 ±1.3 Ma (Xiong et al., 2016), and 217.2±2.0 Ma and 216.2±1.7 Ma (Wang, 2011; Zhu et al., 2011), respectively. The mafic enclaves hosted in the porphyries yield zircon U–Pb ages of 217±2.0 Ma and 218±2.5 Ma (Xiong et al., 2016), respectively. Other data indicates the host porphyries are most likely formed by partial melting of Mesoproterozoic lower continental crust (Qiu et al., 2017). Zircons from the mafic enclaves have negative εHf (t) values ranging from −10.1 to −0.1 and T DM2 of 1052 to 1565 Ma, and have positive ε Hf (t) values of +0.5 to +10.8 and corresponding T DM1 of 441 to 856 Ma (Zhu et al., 2011; Xiong et al., 2016), suggesting an origin by partial melting of Neoproterozoic sub-continental lithospheric mantle (Qiu et al., 2017).
Mineralisation associated alteration at Wenquan is well developed, progressing outward from a potassic core, to a phyllic, and then to propylitic silicate+sulphide+oxide assemblage (Han, 2009). The porphyry-style Mo mineralisation is predominantly composed of stockwork, veinlet and disseminated sulphides. The north-south oriented mineralised zones comprise planar to irregular veins that dip at 30 to 75°NE (Han, 2009). The disseminated Mo mineralisation is generally developed within the biotite granite porphyry and monzogranite porphyry bodies, which contain widespread mafic enclaves. Previous Re-Os dating on molybdenite separated from quartz-molybdenite veins yielded model ages of 214.4 ±7.1 Ma (Song et al., 2008; Zhu et al., 2009) and 219 ±5.2 Ma (Xiong et al., 2016). The molybdenite from quartz-molybdenite veins has Re contents that suggest mantle involvement for the magma and metal source (Song et al., 2008; Zhu et al., 2009).
Estimated resources are 247 Mt @ 0.048% Mo (Qiu et al., 2017),
The information in this summary is drawn from Qiu et al., 2017).
The most recent source geological information used to prepare this decription was dated: 2017.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Wenquan
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Qiu, K.-F., Marsh, E., Yu, H.-C., Pfaff, K., Gulbransen, C., Gou, Z.-Y. and Li, N., 2017 - Fluid and metal sources of the Wenquan porphyry molybdenum deposit, Western Qinling, NW China: in Ore Geology Reviews v.86, pp. 459-473
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