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Open AccessArticle

The Distribution of Precious Metals in High-Grade Banded Quartz Veins from Low-Sulfidation Epithermal Deposits: Constraints from µXRF Mapping

1
Center for Mineral Resources Science, Department of Geology and Geological Engineering, Colorado School of Mines, 1516 Illinois Street, Golden, CO 80401, USA
2
FLUID INC., 1401 Wewatta St. #PH3, Denver, CO 80202, USA
3
Bruker Nano Analytics, 415 N Quay Street, Kennewick, WA 99336, USA
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(12), 740; https://doi.org/10.3390/min9120740
Received: 22 October 2019 / Revised: 24 November 2019 / Accepted: 26 November 2019 / Published: 29 November 2019
High-grade ore zones in low-sulfidation epithermal deposits are commonly associated with the occurrence of banded quartz veins. The ore minerals in these veins are heterogeneously distributed and are mostly confined to ginguro bands, which can be identified in hand specimen based on their distinct dark gray to black color. Micro-X-ray fluorescence element maps obtained on representative samples of banded quartz veins show that Au occurs together with Ag minerals in some of the ginguro bands, but Au can also be present in quartz bands that are light gray to white and cannot be macroscopically distinguished from barren bands. The occurrence of compositionally distinct ginguro and gankin bands, the latter being a new term coined here for colloform quartz bands containing primarily electrum or native gold, can be explained by temporal changes in the composition of the ore-forming thermal waters or variations in the conditions of ore deposition. Textural relationships, including the dendritic shape of ore minerals that appear to have grown in a matrix of silica microspheres, suggest that the ginguro and gankin bands have formed as a result of rapid deposition associated with vigorous boiling or flashing of the thermal waters.
Keywords: low-sulfidation; epithermal; ginguro; µXRF low-sulfidation; epithermal; ginguro; µXRF
MDPI and ACS Style

Tharalson, E.R.; Monecke, T.; Reynolds, T.J.; Zeeck, L.; Pfaff, K.; Kelly, N.M. The Distribution of Precious Metals in High-Grade Banded Quartz Veins from Low-Sulfidation Epithermal Deposits: Constraints from µXRF Mapping. Minerals 2019, 9, 740.

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