Abstract
The Bawang deposit, located in the west of Wuxu ore field, southern section of the Nandan-Hechi metallogenic belt, is a medium-sized tin–zinc polymetallic deposit. Its genesis has been a matter of debate because of lacking constraints from isotope geology. In this study, LA-MC-ICP-MS U-Pb dating of cassiterite and C-O-S-Pb isotope analyses of monominerals were used to investigate the mineralization age and source of the ore-forming minerals in the Bawang deposit. LA-ICP-MS U–Pb dating of cassiterite yielded ages of 93.1 ± 4.8 Ma and 85.3 ± 6.3 Ma, indicating that the mineralization occurred in the early Late Cretaceous. The δ13CPDB and δ18OSMOW values of calcites at the ore stage range between −0.41‰ and 0.44‰ (average = −11‰) and between 13.8‰ and 15.40‰ (average = 14.59‰), respectively. This shows that ore fluid sources were a mixture of those derived from magma and stratum. Pyrite and sphalerite have uniform δ34S values (−4.45‰~−2.20‰), indicating that sulfur is also derived from the mixing of magmatic hydrothermal and stratum fluids. The Pb isotopic composition of sulfide (206Pb/204Pb = 18.4055~18.7625, 207Pb/204Pb = 15.6745~15.7209, 208Pb/204Pb = 38.6232~39.0370) is consistent with the granite of the same age, indicating that ore-forming metals are mainly derived from magmatic hydrothermal solution. The Bawang deposit is a hydrothermal vein-type deposit in the external contact zone of Late Cretaceous granite, controlled by tectonic fractures, and formed by the interaction of magmatic hydrothermal fluid and carbonate rock. There may be large skarn-type ore bodies in the deep part. The results of this study provide insights into the research and exploration of similar deposits in Nandan-Hechi metallogenic belt and in the Youjiang Basin.
Highlights
Chronological information on mineralization is key to understanding the genesis of ore deposits
LA-ICP-MS U-Pb dating of cassiterite has been used to study the metallogenic age of tin polymetallic deposits [1,2,3,4,5,6]
Unlike other stratiform deposits in the area, the stratiform ore bodies are connected with those cutting strata, controlled by the shear faults, which provides an opportunity for studying the genesis of tin polymetallic mineralization from another perspective
Summary
Chronological information on mineralization is key to understanding the genesis of ore deposits. U–Pb isotope chronology was carried out on the Bawang deposit to obtain accurate age data. Supplemented by the study of C-O-S-Pb isotopes, evidence for the sources of mineralized fluids and substances is explored. Most of the previous studies focused on stratiform ore bodies, and the age analysis of ore deposits was mainly concentrated in Dachang ore field. Bawang deposit, located in the west of Wuxu ore field, is a medium-sized tin–zinc polymetallic deposit. Unlike other stratiform deposits in the area, the stratiform ore bodies are connected with those cutting strata, controlled by the shear faults, which provides an opportunity for studying the genesis of tin polymetallic mineralization from another perspective
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