Nature of Crust Constraints on Tin Deposit Distribution in Southwest Yunnan:Based on Hf Isotope Mapping

Pei Tong; Sun Xiang; Zheng Mingjun; Miao Ke; Liang Xiaoya

doi:10.3799/dqkx.2024.133

Abstract：The Southwest Yunnan Tin Belt is one of the most important tin metallogenic belts in China.The temporal and spatial distribution of granite-related tin deposits in the Southwest Yunnan Tin Belt has been summarized,but the relationship between the spatial distribution of tin deposits and the nature of the crust,as well as the reasons for its constraints on tin mineralization,are still unclear.In this paper,published zircon Hf isotope data of Early Paleozoic-Cenozoic granites in Southwest Yunnan are collected.Based on previous large-scale isotope mapping of the Sanjiang Tethys orogenic belt,the εHf(t)value and TDMC contour maps and two typical profiles in Southwest Yunnan are drawn by ArcGIS software.The mapping results show that the Changning-Menglian orogenic belt and Baoshan terrane are ancient crustal domains with low εHf(t)and high TDMC,while the Tengchong terrane has uneven isotopic distribution,and there are both ancient crustal regions with low εHf(t)and high TDMC,as well as newly formed crustal regions with high εHf(t)and low TDMC.The distribution of tin deposits in Southwest Yunnan is closely related to crustal properties.Tin deposits are all distributed in ancient crustal areas with low εHf(t)and high TDMC,while no tin deposits have been found in the newly formed crustal areas with high εHf(t)and low TDMC.The concentrated production of tin ore in ancient crustal regions may be related to ancient tin rich crust.The mixing of low tin and high oxygen fugacity mantle magma has an inhibitory effect on the enrichment of tin in granite,which may be the reason for the unclear tin mineralization in the newly formed crustal area.