Geochemistry and geochronology of porphyries from the Beiya gold–polymetallic orefield, western Yunnan, China

Formation of Au-polymetallic ore deposits in alkaline porphyries at Beiya, Yunnan, Southwest China

“…Three porphyry intrusive events in the area are recognized; the first produced a quartz-albite porphyry at~65 Ma (Xu et al, 2006a); the second a quartz orthoclase porphyry at~37 Ma to 26 Ma (Ying and Cai, 2004;Xu et al, 2006a;Xiao et al, 2009a;He et al, 2013;Liu et al, 2015); the third intrusion to be emplaced was a biotite orthoclase porphyry at~3.78 ± 0.08 Ma (Xu et al, 2006a). The first two stages of porphyry rocks are generally accompanied by lamprophyre dykes (31.6 Ma to 35.5 Ma) (Xu et al, 2006a;Mo and Zeng, 2008).…”

“…They have low total REE concentrations (36-503 ppm, with an average of 134 ppm) and are enriched in light REE with LREE/HREE ratios ranging from 6.09 to 18.21, (La/Yb) N ratios 4.9 to 28.9. The intrusions are enriched in large-ion lithophile elements (e.g., Rb and Ba) and are depleted in high-field-strength elements (e.g., Ta and Hf); there are slight positive Eu-anomalies (δEu = 0.42 to 0.99) (Xu et al, 2006a,b;Mo and Zeng, 2008;Deng et al, in press;Liu et al, 2015).…”

Spatial pattern and dynamic control for mineralization in the Pulang porphyry copper deposit, Yunnan, SW China: Perspective from fractal analysis

“…The multifaceted physicochemical controls of ore fluid on metal precipitation include, among others, redox state and sulfidation state (Einaudi et al, 2003;Zhong et al, 2015), density (Rusk et al, 2008), salinity (Rusk et al, 2008;Yang et al, 2012), composition especially the availability of ligands (chlorine and bisulfide) (Mao et al, 2011a;Seward et al, 2014), and pressure-temperature (Mei et al, 2013;Sillitoe, 2010;Zajacz et al, 2011). As the sulfidation state increases (Barton and Skinner, 1967), fluid temperature drops (Mao et al, 2011b) and fluid immiscibility (Heinrich et al, 1992;Seo et al, 2009) would occur to precipitate metal with the proceeding of mineralization Liu et al, 2015). The propylitic alteration invariably overprints the quartzsericite alteration at different degrees and inevitably further modifies the Cu mineralization.…”

LA-ICP-MS U-Th-Pb Dating and Trace Element Geochemistry of Allanite: Implications on the Different Skarn Metallogenesis between the Giant Beiya Au and Machangqing Cu-Mo-(Au) Deposits in Yunnan, SW China

“…Lamprophyre dikes are also documented in the area. Most of the porphyries were emplaced at around 36.9 to 33.3 Ma [24][25][26]28,[56][57][58][59][60], except for the quartz albite porphyry (65 Ma) and the biotite orthoclase porphyry (3.8 Ma) [45]. The quartz syenite porphyry in the Beiya deposit has been LA-ICP-MS zircon U-Pb dated to be 36.07 ± 0.43 Ma [24], and the retrograde-stage hydrothermal titanite yielded a weighted average 206 Pb/ 238 U age of 33.1 ± 1.0 Ma [61].…”

“…The Emeishan flood basalt is exposed in the southeastern part of the mining area. The regionally-widespread Cenozoic alkaline porphyries include those of (quartz) syenite, biotite-K-feldspar and quartz-albite [26,28,[43][44][45]], yet they are rarely exposed in the Beiya mining district. Major exposed rocks in the Beiya deposit include the Lower Triassic Qingtianbao Formation (175-350 m thick), the Middle Triassic Beiya Formation and Quaternary sedimentary rocks ( Figure 2).…”