Genesis and Prospecting Potential of the Da’anhe Skarn Au Deposit in the Central of the Lesser Xing’an Range, NE China: Evidence from Skarn Mineralogy, Fluid Inclusions and H-O Isotopes

Authors:
raw_author_name: Chuntao Zhao
raw_affiliation_string: College of Earth Science, Jilin University, Changchun 130061, China; Key Laboratory of Green and High-End Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China; Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Xining 810008, China
raw_author_name: Fanting Sun
raw_affiliation_string: College of Earth Science, Jilin University, Changchun 130061, China
raw_author_name: Jinggui Sun
raw_affiliation_string: College of Earth Science, Jilin University, Changchun 130061, China
raw_author_name: Jianping Wang
raw_affiliation_string: Key Laboratory of Green and High-End Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China; Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Xining 810008, China
raw_author_name: Jilong Han
raw_affiliation_string: College of Earth Science, Jilin University, Changchun 130061, China; Development and Research Center of China Geological Survey, Beijing 100037, China
raw_author_name: Dongmei Yu
raw_affiliation_string: Key Laboratory of Green and High-End Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China; Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Xining 810008, China
raw_author_name: Zhikai Xu
raw_affiliation_string: College of Earth Science, Jilin University, Changchun 130061, China
raw_author_name: Lei Yi
raw_affiliation_string: Key Laboratory of Green and High-End Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China; Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Xining 810008, China

Abstract: Skarn Au deposits exist in the circum-pacific metallogenic belt. Interestingly, the Da’anhe Au deposit is the only independent skarn gold deposit in the Lesser Xing’an Range. To determine the metallogenic mechanism and prospecting potential of the Da’anhe deposit, we performed skarn mineralogy, fluid inclusion (FI) and H-O isotope analyses. The results show the following: (1) The Da’anhe deposit is a calcareous reduced skarn Au deposit that formed between an Early Jurassic gabbroic diorite and the Permian Tumenling Formation marble. Its metallogenic process includes five stages: the early skarn stage (Stage I1), late skarn stage (Stage I2), early quartz-sulfide stage (Stage II1), late quartz-sulfide stage (Stage II2) and quartz-carbonate stage (Stage II3). Gold precipitated in Stage II1 and Stage II2. (2) The initial ore-forming fluid was derived from magmatic water and featured a high temperature and intermediate to high salinity. After boiling and mixing, the fluid eventually changed to a low-temperature and low-salinity reducing fluid dominated by meteoric water. (3) The formation depth of the Au orebodies was 2.27-3.11 km, and the orebodies were later lifted to the surface (&lt;500 m). The potential for finding skarn Au deposits in the study area is limited. (4) The distinctive nature of the ore-related magma (i.e., source, reducing conditions and high water content) was key to the formation of the Da’anhe skarn gold deposit.