Origin of Permian gabbroic intrusions in the southern margin of the Altai Orogenic belt: A possible link to the Permian Tarim mantle plume?

• Published in: Lithos Vol. 204; pp. 112 - 124
• Main Authors: Zhang, Chuan-Lin, Zou, Hai-Bo, Yao, Chun-Yan, Dong, Yong-Guan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2014
• Subjects: Geochemistry; Ni–Cu sulfide mineralization; Permian mafic–ultramafic intrusions; Tectonic regime; The Altai orogenic belt; Geochemistry; Permian mafic–ultramafic intrusions; Ni–Cu sulfide mineralization; The Altai orogenic belt; Tectonic regime
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2014.05.019

Zircon U–Pb dating and Hf isotopic compositions, whole-rock and mineral geochemistry, as well as field and petrographic observations, are reported for the Permian gabbroic intrusions in the southern margin of the Altai orogenic belt. Similar zircon ages (~280Ma) of these intrusions to that of the Permian Tarim mantle plume suggest a possible link to the Tarim plume. Olivine grains from the intrusions have Fo contents ranging from 69 to 81 and NiO from 0.05 to 0.21wt.%, indicating the crystallization from evolved mafic magmas. Clinopyroxene grains from the intrusions have 0.3 to 1.5wt.% TiO2 and display a rift- to arc-like affinity. The intrusions are tholeiitic and have slightly LREE-depleted to LREE-enriched chondrite-normalized rare earth element (REE) patterns. Zircons from the intrusions have εHf(t) values higher than+8.0, whereas the whole-rock εNd(t) values range from +2.7 to +7.0. Rocks from the intrusions have Nb/La of 0.2 to 0.8, consistent with the derivation from a depleted sub-lithospheric mantle with variable degrees of crustal contamination. The presence of primary hornblende and/or biotite in the rocks indicates metasomatism by slab-derived fluids/melts in the mantle source. We propose that upwelling of asthenospheric mantle in the Permian Tarim mantle plume along the Irtish suture zone, resulted in partial melting of the sub-continental lithospheric mantle. Based on a comparison between the Ni–Cu sulfide-bearing Kalatongke complex and un-mineralized intrusions, we suggest that Ni–Cu sulfide mineralized intrusions in the Altai orogenic belt are characterized by the enrichments of LREEs and LILEs and by the presence of primary water-bearing minerals. [Display omitted] •Age and geochemistry of the Permian gabbroic intrusions in Altai are reported;•The coeval gabbroic intrusions are derived from a common metasomatised lithosphere induced by heat from Permian Tarim plume;•A geochemical proxy for the metallogenesis for the Permian ultramafic–mafic intrusions within the Permian Tarim LIP is proposed.