Petrology, mineral chemistry, and geochemistry of Late Triassic Ni–Cu ore-bearing mafic–ultramafic intrusions, Hongqiling, northeastern China: petrogenesis and tectonic implications

Abstract

The Hongqiling magmatic Ni–Cu sulfide deposit, situated on the southern margin of the eastern Central Asian Orogenic Belt (CAOB), is composed of over 30 mafic–ultramafic intrusions. These ore-bearing intrusions are composed mainly of harzburgite, lherzolite, websterite, orthopyroxenite, and norite (gabbro). The constituent minerals are olivine, diopside, bronzite, calcic-hornblende, plagioclase, and spinel with orthopyroxene as a dominant mineral in these intrusions. These ore-bearing intrusions are not Alaskan-type complexes. Spinel and clinopyroxene both exhibit different chemical compositions from those in the Alaskan-type complexes. The rocks that make up the intrusions have high contents of MgO (average value = 25.20 wt.%) and low TiO2 (average value = 0.58 wt.%). The high MgO contents of the minerals and the high Mg# (71) of the calculated melt in equilibrium with olivine demonstrate that the parental magma of the Hongqiling mafic–ultramafic intrusions was a high-Mg tholeiitic magma. The Hongqiling ore-bearing mafic–ultramafic intrusions and the calculated “trapped liquids” for the olivine-orthopyroxene cumulate rocks are all enriched in large-ion lithophile elements and depleted in high field strength elements. The Ce/Pb, Ta/La, Th/Yb, and (La/Sm)PM values and the depletion of Nb and Ta suggest that the magma experienced crustal contamination. The Hongqiling ore-bearing intrusions display many similarities with mafic–ultramafic intrusions that formed in a post-collisional extensional environment in the western CAOB (e.g., Huangshanxi). Common features include their whole-rock compositions and mineral chemistry. Combined with the evolutionary history of the eastern segment of the CAOB, we believe that the Late Triassic Hongqiling mafic–ultramafic intrusions formed in a post-collisional extensional environment.

The parental magma composition, crustal contamination process, and metallogenesis of the Shitoukengde Ni‐Cu sulfide deposit in the Eastern Kunlun Orogenic Belt, NW China

“…It is generally characterized as follows: a) As consisting of several coeval small‐scale (~1 km 2 ) complexes/intrusions, most of which are distributed in groups and bands in the region; b) by a complex shape that is mainly a stock or small rock basin with obvious dipping and lateral trending; and c) by Cu–Ni mineralization that is mainly hosted in small‐scale ultramafic intrusions that intrude gabbro or wall rock, at a high mineralization rate. Such Cu–Ni deposits in China are mainly distributed in Xinjiang Province (e.g., Kelatongke, Huangshan, Huangshandong, Huangshannan, Tulaergen, Poshi, and Poyi; Zhang et al ., 2008; Song and Li, 2009; Deng et al ., 2011; Xie et al ., 2011; Gao et al ., 2012; Feng et al ., 2014; Mao et al ., 2014a, 2014b, 2015, 2016, 2017; Zhao et al ., 2017; Liu et al, 2017, 2018), Qinghai Province (e.g., Xiarihamu, Langmuri, Akechukesai, and Niubiziliang; Li et al ., 2012, 2015; Zhao et al ., 2012; Wang et al ., 2014; Chai and Shang, 2018; Yu et al ., 2019; Yan et al ., 2020), and Jilin Province (e.g., Hongqiling, Piaohechuan, and Changren; Lv et al ., 2011, 2012; Piao et al ., 2011; Wei et al ., 2015; Li et al ., 2019; Xue, 2020), and many of them are economically viable or actively mined. They typically form from pulses of magma injection and are extensively mineralized (Tang, 1990, 1995, 1996, 2002; Tang and Li, 1991; Tang et al ., 2006; Li et al ., 2012; Wang et al ., 2014; Li, 2018), and the metallogenic mechanism of those from Qinghai Province have a very high similarity of “deep liquation–pulsing injection” to the Jinchuan deposit (Li, 2018).…”