The Gaojiacun Mafic-Ultramafic Complex （Sichuan, SW China）：Neoproterozoic Magmatic Activity at the Western Margin of the Yangtze Craton

1 Introduction The Gaojiacun intrusive complex is one of the numerous ultramafic-mafic intrusions in Sichuan Province of China. It was mapped during the 1970s and studied mainly by Chinese scientists (e.g. Geological Team 106, 1975; Shen et al., 1986, 1989; CGGJC, 1986; Yang et al., 1993; Li et al., 1995; Shen et al., 2003; Zhu et al., 2004a). Since the year 2000, China has become one of the largest PGE consumers. While the country can produce only less than 1 ton PGE/year, the Chin…

The Gaojiacun Mafic-Ultramafic Complex(Sichuan,SW China):Neoproterozoic Magmatic Activity at the Western Margin of the Yangtze Craton

Abstract: The Neoproterozoic Gaojiacun intrusive complex (GIC) is composed of one big intrusion (ca. 9 times 7.5 km) and numerous satellite intrusions, emplaced in the low‐grade schists of the Neoproterozoic Yanbian Group. The main intrusion is concentrically zoned, with peridotite bodies + leucogabbroids in its core (inner zone) and the sequence: olivine hornblende gabbronorite ? porphyric pyroxene hornblende gabbronorite (transitional zone) ‐ pyroxene hornblende gabbronorite + hornblende gabbro + diorite (outer zone), towards the margins. The satellite intrusions are composed either of a single rock type (peridotite, gabbro, diorite or granite) or of different rock types (peridotite + diorite + granite). Upper crustal contamination is evidenced by the occurrence of numerous metamorphic enclaves, migmatites and mixed rocks in the outer zone of the main intrusion and in the satellite intrusions. Hornblende (often oikocrystic) is present in all mafic and ultramafic rocks. Cu‐Ni (‐PGE) deposits occur in several satellite intrusions, hosted in peridotite. The geochemical and mineralogical features of GIC support the presence of a subduction zone at the western edge of the Yangtze Craton. A feeder‐related genesis of the satellite intrusions is inferred.