Mineral chemistry and genesis of the Permian Cihai and Cinan magnetite deposits, Beishan, NW China
MetadataShow full item record
Cihai and Cinan are Permian magnetite deposits related to mafic-ultramafic intrusions in the Beishan region, Xinjiang, NW China. The Cihai mafic intrusion is dominantly composed of dolerite, gabbro and fine-grained massive magnetite ore, while gabbro, pyrrhotite + pyrite-bearing clinopyroxenite and magnetite ore comprise the major units in Cinan. Clinopyroxene occurs in both deposits as 0.1–2 mm in diameter subhedral to anhedral grains in dolerite, gabbro and clinopyroxenite. High FeO contents (11.7–28.9 wt%), low SiO2 (43.6–54.3 wt%) and Al2O3 contents (0.15–6.08 wt%), and low total REE and trace element contents of clinopyroxene in the Cinan clinopyroxenite imply crystallization early, at high pressure. This clinopyroxene is FeO-rich and Si and Ti-poor, consistent with the clinopyroxene component of large-scale Cu-Ni sulfide deposits in the Eastern Tianshan and Panxi ares, as well as Tarim mafic intrusion and basalt, implying the Cinan mafic intrusion and sulfide is related to tectonic activity in the Tarim LIP. The similar mineral chemistry of clinopyroxene, apatite and magnetite in the Cihai and Cinan gabbros (e.g., depleted LREE, negative Zr, Hf, Nb and Ta anomalies in clinopyroxene, lack of Eu anomaly in apatite and similarity of oxygen fugacity as indicated by V in magnetite), indicate similar parental magmatic characteristics. Mineral compositions suggest a crystallization sequence of clinopyroxenite/with a small amount of sulfide – gabbro – magnetite ore in the Cinan deposit, and magnetite ore – gabbro – dolerite in Cihai. The basaltic magma was emplaced at depth, with magnetite segregation (and formation of the Cinan magnetite ores) occurring in relatively low fO2 conditions, after clinopyroxenite and gabbro fractional crystallization. The evolved Fe-rich basaltic magma rapidly rose to intermediate or shallow depths, forming an immiscible Fe-Ti oxide magma as fO2 increased and leaving a Fe-poor residual magma in the chamber. The residual magmas was emplaced at different levels in the crust, forming the Cihai gabbro and dolerite, respectively. Finally, the immiscible Fe-Ti oxide magma was emplaced into the earlier formed dolerite because of late magma pulse uplift, resulting in a distinct boundary between the magnetite ores and dolerite.
Showing items related by title, author, creator and subject.
Genesis of the Permian Kemozibayi sulfide-bearing mafic-ultramafic intrusion in Altay, NW China: Evidence from zircon geochronology, Hf and O isotopes and mineral chemistryTang, D.; Qin, K.; Xue, S.; Mao, Y.; Evans, Noreen; Niu, Y.; Chen, J. (2017)Â© 2017 Elsevier B.V. The recently discovered Kemozibayi mafic-ultramafic intrusion and its associated magmatic Cu-Ni sulfide deposits are located at the southern margin of the Chinese Altai Mountain, Central Asian Orogenic ...
Genesis of ilmenite-series I-type granitoids at the Baogutu reduced porphyry Cu deposit, western Junggar, NW-ChinaCao, M.; Qin, K.; Li, G.; Evans, Noreen; Hollings, P.; Jin, L. (2016)© 2016 Elsevier B.V. The Baogutu porphyry Cu deposit is a typical reduced porphyry Cu deposit, likely related to ilmenite-series I-type granitoids. However, the nature of the granitoids (ilmenite-series or magnetite-series) ...
Physicochemical processes in the magma chamber under the Black Mountain porphyry Cu-Au deposit, Philippines: Insights from mineral chemistry and implications for mineralizationCao, Mingjian; Hollings, P.; Cooke, D.; Evans, Noreen; McInnes, Brent; Qin, K.; Li, G.; Sweet, G.; Baker, M. (2018)Â© 2018 Society of Economic Geologists, Inc. The Black Mountain porphyry Cu-Au deposit in the Baguio district, Northern Luzon (Philippines) is associated with late Miocene to Pliocene intrusive rocks that retain primary ...