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Fluid compositions reveal fluid nature, metal deposition mechanisms, and mineralization potential; an example at the Haobugao Zn-Pb skarn, China

Shu Qihai, Zhaoshan Chang and John Mavrogenes
Fluid compositions reveal fluid nature, metal deposition mechanisms, and mineralization potential; an example at the Haobugao Zn-Pb skarn, China
Geology (Boulder) (December 2020) 49 (4): 473-477

Abstract

Fluid inclusion compositions obtained from laser ablation-inductively coupled plasma-mass spectrometry at the Haobugao Zn-Pb skarn in northeastern China provide constraints on fluid origin, evolution, and metal deposition mechanisms and an example of evaluating mineralization potential. Metal concentrations in the prograde fluids were high (up to 1.4 wt% Zn and 1.8 wt% Pb) but remained in solution, likely due to the high temperatures (440-575 degrees C) and salinities (35.4-45.3 wt% NaCl equivalent). Absolute concentrations of elements (e.g., Rb and Na) and mass ratios (e.g., Zn/Na and K/Na) reveal that the early, prograde fluids were magmatic, consistent with the oxygen isotope composition of fluids (delta (super 18) O (sub H2O) =5.5 ppm-8.5 ppm). Later mixing with a meteoric fluid caused dilution and Zn-Pb deposition, as revealed by lowered element concentrations and Pb/(Na+K) and Zn/(Na+K) ratios in the sulfide-stage fluid inclusions. Elevated Ca/K ratios in sphalerite-hosted inclusions indicate fluid-carbonate reactions that buffered fluid pH, also facilitating Zn-Pb precipitation. Although cassiterite and molybdenite occur locally at Haobugao, mass balance calculation shows low metal endowment (maximum 2900 t Sn and 2200 t Mo) of the system. Furthermore, the generally unchanged Sn/(Na+K) and Mo/(Na+K) ratios from pre- to late-mineralization fluids suggest that the fluids were never saturated in Sn and Mo. Therefore, finding much Sn or Mo at Haobugao is unlikely. This demonstrates a potential tool for evaluating the metal endowment of a mineral prospect, which may guide exploration.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 49
Serial Issue: 4
Title: Fluid compositions reveal fluid nature, metal deposition mechanisms, and mineralization potential; an example at the Haobugao Zn-Pb skarn, China
Affiliation: China University of Geosciences, School of Earth Sciences and Resources, Beijing, China
Pages: 473-477
Published: 20201211
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 37
Accession Number: 2021-011644
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N37°40'00" - N53°30'00", E98°00'00" - E126°00'00"
Secondary Affiliation: James Cook University, AUS, AustraliaAustralian National University, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202108
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