Geological, Geochemical And Metallogenic Characteristics Of The Ultramafic Intrusions In Panxi District

This paper has concluded the geological and geochemical characteristics as well as metallogenic characteristics of several typical ultramafic intrusions in Panxi district including Yangliuping, Limahe, Baimazhai, Zhubu, Jinbaoshan, Lengshuiqing. By comparing the geological, geochemical and ore-bearing characteristics of these intrusions, we discussed the source and magmatism and ore-forming process of the intrusions, along with the correlation among them in this region. The cognition that we preliminarily got include the following:1. The ultramafic intrusions in Panxi district could be divided into two categories according their formation age:Lengshuiqing intrusion is formed in Neoproterozoic (～821Ma); Yangliuping, Limahe, Baimazhai, Zhubu and Jinbaoshan intrusions are formed in Late Permian, Which is generally consistent with the age of ELIP (251-263Ma).2. Each ultramafic intrusion in Panxi district has different scale and attitude, the relationship between ore body and the intrusion is very close. The intrusions are primarily consists of ultramafic rocks, including peridotite, pyroxenite, gabbro, and the transitional type among them, the ore has massive, disseminated and banded structure as well as sideronitic texture.3. The ultramafic intrusions in Panxi district have different ore-bearing features:Yangliuping is a Cu-Ni-PGE deposit; Limahe, Baimazhai, Lengshuiqing belong to Cu-Ni deposits which are depleted in PGE; Jinbaoshan and Zhubu belong to sulfide barren PGE deposit.4. The trace elemental geochemistry of intrusions in Panxi district is found to be similar except Lengshuiqing intrusion. The trace elemental geochemistry of those intrusions could be well compared with that of Emeishan LT basalts and OIB, which indicate the mantle plume source of LT basalts and Yangliuping, Limahe, Baimazhai, Zhubu, Jinbaoshan intrusions. Lengshuiqing intrusion has been obviously influenced by crust subduction slab or fluid. The anomaly of Nb, Ta and Sr-Nd, Re-Os, S isotopic characteristics show that the primary magma has experienced the process of crustal contamination, the relationship of PGE elements in rocks which don’t contain ore mineral indicate the process of sulfide segregation, and the different Cu/Pd value could tell the time of sulfide segregation process and the different S saturation level. Varying degrees of crutal contamination and S saturation level probably lead to the various ore-bearing features.4. The ultramafic intrusions and deposits in Panxi district are product of different S saturation level of magma. The intrusions which represent different S saturation level of magma may be contiguous before they were separated by tectonization.