Greenockite and Associated Sulfide Mineralization From the Caledonia Group Mines, Blanca Creek, La Huerta Range, San Juan Province, Argentina

Abstract

We document various textural occurrences of greenockite associated with several ore minerals in varying parageneses: pyrite + sphalerite + galena + chalcopyrite ± arsenopyrite ± pyrrhotite ± bornite ± tennantite ± tetrahedrite ± covellite ± chalcocite ± aikinite ± wittichenite ± matildite ± berryite ± miharaite ± geocronite ± hematite ± magnetite from mineralized samples of the Caledonia Group mines, Marayes mining district, La Huerta Range, San Juan province, Argentina, based on reflected light and scanning electron microscope investigations. The mineralization is hosted mainly in metacarbonate outcrops in contact with the granulite basement and associated intermediate to mafic meta-intrusive rocks. We recognize three types of greenockite on the basis of textural and chemical criteria. Type-1 greenockite contains less than 1 mol.% ZnS, but its Fe content varies from 0.2 up to 4.5 mol.% FeS. Type 2 is Zn-rich, with 10-25 mol.% ZnS component and <0.1 to 3 mol.% FeS component, and type 3 has a Zn content of 5-7 mol.% ZnS component and FeS <0.1 mol.%. The presence of complex Ag-Cu-Bi-Pb sulfides point to a latestage, low-temperature overprint of the primary sulfide parageneses, accompanied by the formation of hypogene greenockite, at least partly at the expense of sphalerite. The near-end-member composition of greenockite and late-stage sphalerite also indicates a low temperature of formation.

A New Zincian Greenockite Occurrence in the Saishitang Cu Skarn Deposit, Qinghai Province, Northwest China

“…The Zn content varied (5.61 to 21.7 mol % ZnS), similarl to other occurrences of greenockite in hydrothermal deposits [4,11], e.g., 6-11 mol % ZnS in the Madjarovo Pb-Zn deposit [21], the maximum difference in different types of greenockite in the Caledonia Group being <1 to 25 mol % ZnS [11], and 42-59 mol % ZnS in the Tsumeb, southwest Africa [17]. In comparison to other occurrences, the zincian greenockite in the Saishitang deposit could be divided into two phases (I and II).…”

“…The EPMA data indicated that zincian greenockite contains 72.4-89.9 mol % CdS, which was in accordance with the experimental data of the ZnS-CdS system at 250 °C [7], and furthermore, the composition and structure were in line with the greenockite series [45] (cited in [2]). The Zn content varied (5.61 to 21.7 mol % ZnS), similarl to other occurrences of greenockite in hydrothermal deposits [4,11], e.g., 6-11 mol % ZnS in the Madjarovo Pb-Zn deposit [21], the maximum difference Figure 11. Compositions of cobaltite in the system of CoAsS-FeAsS-NiAsS, mol % (after [44]).…”

“…Experimental studies of the system ZnS-CdS have indicated the existence of a complete solid solution at temperatures above 600 • C [4][5][6][7][8][9][10]. It has been shown that the solid solution exists to an extent at hydrothermal conditions below 400 • C [4], and that the replacement of Cd by Zn is a rather complicated process that is dependent on the formation environment [11].…”

“…However, greenockite also occurs as a primary mineral in various geological settings [4,11,12], including (i) pegmatites [13], (ii) granites [14], (iii) fumaroles [2], (iv) chromite-PGE mineralization [12], (v) hydrothermal ore deposits [4,11], (vi) estuarine sediments [15,16], and (vii) shales [17]. The predominant occurrences of greenockite in hydrothermal deposits are in Pb-Zn deposits, such as sediment-hosted Pb-Zn deposits [18,19], volcanic-related Pb-Zn deposits [20][21][22], as well as a few in orogenic Au deposits [23] and epithermal Au-Ag deposits [4,24].…”

“…Greenockite is formed predominantly as a weathering product of Cd-bearing sphalerite [11]. However, greenockite also occurs as a primary mineral in various geological settings [4,11,12], including (i) pegmatites [13], (ii) granites [14], (iii) fumaroles [2], (iv) chromite-PGE mineralization [12], (v) hydrothermal ore deposits [4,11], (vi) estuarine sediments [15,16], and (vii) shales [17].…”