Tennantite–Tetrahedrite-Series Minerals and Related Pyrite in the Nibao Carlin-Type Gold Deposit, Guizhou, SW China

Autor: Qinping Tan, Yong Xia, Dong-Tian Wei, Zhuojun Xie, Ling’an Bai, Xi-jun Liu, Jeffrey A. Steadman
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Minerals
Volume 11
Issue 1
Minerals, Vol 11, Iss 2, p 2 (2021)
ISSN: 2075-163X
DOI: 10.3390/min11010002
Popis: A number of sediment-hosted, Carlin-type/-like gold deposits are distributed in the Youjiang basin of SW China. The gold ores are characterized by high As, Hg, and Sb contents but with low base metal contents (Cu+Pb+Zn <
500&ndash
1000 ppm). The Nibao deposit is unique among these gold deposits by having tennantite&ndash
tetrahedrite-series minerals in its ores. The deposit is also unique in being primarily hosted in the relatively unreactive siliceous pyroclastic rocks, unlike classic Carlin-type gold deposits that are hosted in carbonates or calcareous clastic rocks. In this study, we have identified tennantite-(Zn), tennantite-(Hg), and tetrahedrite-(Zn) from the tennantite&ndash
tetrahedrite-series mineral assemblage. The tennantite-(Zn) can be further divided into two sub-types of Tn-(Zn)-I
and Tn-(Zn)-II
Tn-(Zn)-I
usually occurs in the core of a Tennantite&ndash
tetrahedrite composite and appears the darkest under the SEM image, whereas Tn-(Zn)-II overgrows on Tn-(Zn)-I and is overgrown by tetrahedrite-(Zn). Tennantite-(Hg) occasionally occurs as inclusions near the uneven boundary between Tn-(Zn)-I and Tn-(Zn)-II. An appreciable amount of Au (up to 3540 ppm) resides in the tennantite&ndash
tetrahedrite-series minerals, indicating that the latter is a major Au host at Nibao. The coexistence of tennantite&ndash
tetrahedrite-series minerals and Au-bearing pyrite indicates the Nibao ore fluids were more oxidized than the Carlin-type ore fluids. The tennantite&ndash
tetrahedrite series at Nibao evolved from Tn-(Zn)-I through Tn-(Zn)-II to tetrahedrite-(Zn), which is likely caused by Sb accumulation in the ore fluids. This indicates that the Nibao ore fluids may have become more reduced and less acidic during Au precipitation.
Databáze: OpenAIRE
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