Structural, lithological, and geochemical constraints on the dynamic magma plumbing system of the Jinchuan Ni–Cu sulfide deposit, NW China

• Published in: Mineralium deposita 2012-03, Vol.47 (3), p.277-297
• Main Authors: Song, Xie-Yan, Danyushevsky, Leonid V., Keays, Reid R., Chen, Lie-Meng, Wang, Yu-Shan, Tian, Yu-Long, Xiao, Jia-Fei
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Immiscibility; Lithology; Magma; Mineral Resources; Mineralogy; Plumbing; Rocks; Sulfides
• ISSN: 0026-4598; 1432-1866
• DOI: 10.1007/s00126-011-0370-7

Eastern and western portions of the Jinchuan ultramafic intrusion have previously been interpreted as dismembered segments of a single elongate intrusion by late faults. However, the different stratigraphic sequences of the two portions indicate that they are originally two separate intrusions, referred to as Eastern and Western intrusions in this study. The Eastern intrusion is characterized by a concentric distribution of rock types with a core of sulfide dunite enveloped by lherzolite, whereas the Western intrusion is composed of the Upper and Lower units, interpreted as magmatic mega cycles with regular variations in lithology and chemistry. In the Western intrusion, the Upper unit consists of fine-grained dunite, lherzolite, and pyroxenite from its base to its top. The MgO contents decrease upward from the dunites (42–45 wt.%) to the lherzolites (36–41 wt.%), while Al 2 O 3 and incompatible elements increase upward. In contrast, the Lower unit consists of coarse-grained dunites and lherzolites containing 37–40 and 28–35 wt.% MgO, respectively. Sharp contacts between the Upper and Lower units and fine-grained dunite xenoliths at the top of the Lower unit indicate that the Lower unit intruded along the base of the Upper unit. Disseminated and net-textured sulfides primarily occur in the Lower unit and comprise the no. 24 ore body. Very low S contents (