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

Abstract

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 < 500–1000 ppm). The Nibao deposit is unique among these gold deposits by having tennantite–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–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–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–tetrahedrite-series minerals, indicating that the latter is a major Au host at Nibao. The coexistence of tennantite–tetrahedrite-series minerals and Au-bearing pyrite indicates the Nibao ore fluids were more oxidized than the Carlin-type ore fluids. The tennantite–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.

Tennantite-(Hg), Cu6(Cu4Hg2)As4S13, a new tetrahedrite-group mineral from the Lengenbach quarry, Binn, Switzerland

“…Following the approval of tennantite-(Hg) from the Lengenbach quarry, two other occurrences have been reported. Wei et al (2021) described tennantite-(Hg) (Hg up to 1.34 apfu), as μm-sized (~ 1-2 μm) grains associated with tennantite-(Zn), from the Nibao Carlintype Au deposit, Guizhou (China), whereas Ansermet et al (2021) (N. Meisser, pers. comm.…”

“…Following the approval of tennantite-(Hg) from the Lengenbach quarry, two other occurrences have been reported. Wei et al (2021) described tennantite-(Hg) (Hg up to 1.34 apfu), as μm-sized (∼1-2 μm) grains associated with tennantite-(Zn), from the Nibao Carlin-type Au deposit, Guizhou, China, whereas Ansermet et al (2021) reported tennantite-(Hg) from the Chandolin Alp, Valais, Switzerland, as a 70 μm anhedral grain associated with gold, bismuth, covellite, hessite, spionkopite and chalcocite, all included in bornite. On the basis of energy-dispersive spectroscopy analyses, the chemical formula, recalculated assuming ΣMe = 16 apfu, is Cu 9.62 Hg 2.02 (As 4.05 Sb 0.31 ) Σ4.36 S 13.37 (N. Meisser, pers.…”

Geology, mineralogy and geochemistry of Tavt gold deposit in Dzhida zone, northern Mongolia: implications for the evolution of intrusion and ore mineralization

“…Recently, Wei et al, (2021) reported that tennantite could act as one of major Au-bearing ore minerals, suggesting that its coexistence with Au-bearing pyrite might indicate derivation from oxidized hydrothermal fluids. The presence of tennantite was suggested to be an indicator of magmatic-hydrothermal origin of ore-forming fluids (Staude et al, 2010).…”

Sm–Nd Isochron Age Constraints of Au and Sb Mineralization in Southwestern Guizhou Province, China

“…The Youjiang basin hosts clusters of Carlin-type Au, Sb, and Hg-Tl deposits (Figure 1) [1][2][3][4][5][6][7][8], such that it is the second largest low-temperature Carlin-type Au mineralized area in the world, after Nevada, USA [9][10][11][12][13]. The Au and Sb deposits in the Youjiang Basin are primarily located within Southwestern Guizhou and account for more than 70% of the deposits and endowments.…”