Speaker: Mr. Andrew Steiner will be giving GSN Elko Chapter’s February 2021 virtual talk on his PhD research at the University of British Columbia.
Title: “Episodic fluid flow and roll-fronts: insights on the formation of Carlin-type Au-deposits from ore-stage carbonate veins in the Nadaleen trend, Yukon”
Carlin-type Au-deposits (CTGDs) are economically significant hydrothermal deposits that form when Au-bearing hydrothermal fluids interact with carbonate host-rocks. Decades of research on CTGDs in northern Nevada have constrained some critical processes that helped form CTGDs, such as the sulfidation of carbonate-bound Fe as a Au-deposition mechanism. However, several processes that govern CTGD genesis remain poorly understood, including the source of Au and ore-fluids.
In this talk, I will present recent research results from the CTGDs of the Nadaleen trend, Yukon. These deposits offer an opportunity to study CTGDs away from Nevada to understand what processes are truly ubiquitous to CTGD formation. In the Nadaleen trend, several carbonate veins fluoresce under UV light. These UV-fluorescent (UVF) veins have distinct physical, chemical and isotopic properties that indicate that they formed from ore-stage hydrothermal fluids.
These properties provide insights into the pathways the fluids exploited, the temperature of ore-fluids, the processes by which the fluids dissolved and precipitated carbonate, and the timing of hydrothermal fluid flow. Based on these results, we present a “roll-front” model for CTGD formation in which carbonate is continually being dissolved and mobilized down the flow path. The high-permeability decarbonatized zone allows upstream fluids constant access to the hydrothermal front that enables the fluids to dissolve vast quantities of carbonate. Downstream from this dissolution zone, the fluids precipitated carbonates with high Mn and low Sr contents that have C and O isotopic compositions that vary from the wall-rock. We also use U-Pb carbonate geochronology to show that realgar-bearing UVF veins formed in several episodes during the Late Cretaceous to the Oligocene and discuss implications for this timing on genetic models for CTGD formation both in Yukon and Nevada.
Topic: GSN Elko February Meeting, Andrew Steiner, Univ. of BC
Date & Time: Feb 18, 2021 7:00 PM Pacific Time (US and Canada)
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Details02/18/2021 19:00:0002/18/2021 20:30:00America/Los_AngelesGSN Elko Chapter Meeting – Thursday, Feb. 18, 2021 @ 7:00 p.m.Reno, NV
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