Platinum Group Elements Geochemistry of Two Mafic-Ultramafic Intrusions in the Beishan Block, Xinjiang, NW China
详细信息
- 责任者：Chai Fengmei (Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt ; College of Geology and Mining Engineering ; Xinjiang University ; Urumqi 830049 ; China) ; Xia Fang
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(4)
- 页码：p.474-485
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
PGE geochemistry of the Poyi and Luodong Ni-Cu sulphide-bearing mafic-ultramafic intrusions in the Beishan was analyzed in this study. The results show two intrusions have low total PGE contents, ranging from 2.15×10-9 to 18.66×10-9 in Poyi intrusion and 0.55×10-9 to 3.18×10-9 in Luodong intrusion, respectively, with PPGE higher than IPGE. The PGE primitive mantle-normalized patterns display a positive slop and low fractionation between IPGE and PPGE, and negative Ir and Rh anomalies. The PGE, Cu and Ni are depleted relative to the primitive mantle with low and narrow Pd/Ir ranges (3.47~7.35 and 9.73~20.67), indicating the magma contamination. The relationship between Ni/Cu and Pd/Ir indicates that the primary magma was high-magnesium tholeiitic. The Cu/Pd and Ti/Pd ratios of these rocks suggest that the primary magmas have undergone segragation of sulfide before their emplacement.The obviously positive correlation between Cr and Ni, Ir in the Luodong intrusion shows that fractionation crystallization of olivine and chromite made key contribution to sulfur saturation of the magma, with inconspicuous effect over sulfide segregation in the Poyi intrusion. Based on the PGE model calculations, calculated R values suggest that the two intrusions are of potential of medium-scale Ni deposit.