Analyses of major and trace elements of zircons and amphiboles in the Sanligang quartz diorite in the northern margin of Yangtze block

The Neoproterozoic magmatic activities in the South China Block may be related to the assembly and breakup of the Rodinia supercontinent. There are some recently discovered magmatic intrusions of the early to middle Neoproterozoic in the Dahongshan area in the northern margin of the Yangtze Block. These intrusions may provide key evidences for revealing the paleogeographic frameworks and tectonic evolution processes of the northern margin of the Yangtze Block, and possible connections between the South China Block and the Rodinia supercontinent. In this work, we conducted the zircon geochronological study, in-situ analysis of major and trace elements of zircons and amphiboles, and geochemical study of bulk rock samples of the Sanligang quartz diorite in the northern margin of the Yangtze Block. The LA-ICP-MS U-Pb dating results of zircons from the quartz diorite, combined with previous geochronological results, show that the Sanligang granitoid pluton was formed in the early Neoproterozoic (883-858 Ma). The calculated crystallization temperatures and pressures, water contents and oxygen fugacities of the magma, based on relevant data of zircons and amphiboles from the Sanligang quartz diorite in the northern margin of the Yangtze Block, vary from 757 ℃ to 774 ℃, from 1.5×108 Pa to 2.4×108 Pa, from 5.57% to 5.61%, and ΔFMQ+0.85 to ΔFMQ+1.10, respectively. These analytical results indicate that the environment during the crystallization of magma of the Sanligang quartz diorite in the Dahongshan area was characterized by relatively low temperature, relatively low pressure, high oxygen fugacity, and water-enriched magma. This means that the magma crystallization occurred at a relatively shallow depth. The compositional characteristics of the quartz diorite samples are similar to those of trace elements of the average upper crust, with the enrichment of strongly incompatible elements and light rare earth elements, and the depletion of high field strength elements, indicating that Sanligang quartz diorite could be formed in a continental arc environment.