Study on the spatial distribution, occurrence and enrichment of Co-Se-Te in the Xinqiao deposit of Tongling ore cluster, Anhui Province

摘要

Xinqiao deposit is a typical large stratiform skarn-type copper-gold-polymetallic deposit located in Tongling ore cluster within the Middle -Lower Reaches of the Yangtze River Metallogenic Belt. In addition to the enrichment of copper, gold, iron and sulfur, critical elements such as cobalt, selenium and tellurium are also enriched during the mineralization process. Previous studies have conducted many researches on the Xinqiao deposit, but systematic investigations on the distribution patterns, occurrence states and enrichment mechanisms of cobalt, selenium and tellurium in the deposit have not been carried out. In this study, representative rock and ore samples were collected from two profiles (3804 and E601) located at different distances from the ore-forming rock body. Analytical techniques such as optical microscopy, scanning electron microscopy, whole -rock major and trace element analysis and in-situ LA-ICP-MS trace element testing of minerals were employed to find out the spatial distribution patterns and occurrence states of cobalt, selenium and tellurium in the deposit. Subsequently, the enrichment mechanisms of cobalt, selenium and tellurium was preliminarily explored. The estimated resources of associated cobalt, selenium and tellurium in the Xinqiao deposit are approximately 2,326 tons, 2,590 tons and 1,463 tons, respectively, reaching a large to medium-sized scale. In the near-mineralization ( thermal) center (3804 profile), the content of cobalt and selenium decrease gradually from the bottom to the top of the orebody, and there is no obvious pattern of change in tellurium content. Cobalt, selenium and tellurium are predominantly enriched in pyrite ores. In the farmineralization ( thermal) center ( E601 profile), the content of cobalt, selenium and tellurium also decrease gradually from the bottom to the top of the orebody and are mainly enriched in high grade pyrite ores. Along the strike of orebody from the mineralization ( thermal) center to the distal end, the cobalt content decreases significantly, while the selenium and tellurium content relatively increase. Cobalt and selenium in the deposit mainly occur in the form of isomorphic replacement in pyrites, while tellurium occurs mainly as independent telluride minerals, including hessites and tellurites. Cobalt is mainly enriched during the quartz -sulfide stage, with high -temperature ore -forming fluid. Most of the cobalt in the fluid precipitates and enriches in pyrite ores in the near-mineralization ( thermal) center. During the carbonate -sulfide stage, as the ore -forming fluid temperature decreases, most of the selenium and tellurium in the fluid precipitates and accumulates in high grade pyrite ores in the far-mineralization ( thermal) center. Selenium is mainly enriched through abundant precipitation in pyrites, while tellurium enters sulfides such as pyrites in smaller amount and is primarily present as independent minerals.

关键词