Trace elements in hydrothermal quartz: relationships to cathodoluminescent textures and insights into vein formation

Rusk, Brian G., Lowers, Heather A., and Reed, Mark H. (2008) Trace elements in hydrothermal quartz: relationships to cathodoluminescent textures and insights into vein formation. Geology, 36 (7). pp. 547-550.

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Abstract

High-resolution electron microprobe maps show the distribution of Ti, Al, Ca, K, and Fe among quartz growth zones revealed by scanning electron microscope-cathodoluminescence (SEM-CL) from 12 hydrothermal ore deposits formed between ~100 and ~750 °C. The maps clearly show the relationships between trace elements and CL intensity in quartz. Among all samples, no single trace element consistently correlates with variations in CL intensity. However in vein quartz from five porphyry-Cu (Mo-Au) deposits, CL intensity always correlates positively with Ti concentrations, suggesting that Ti is a CL activator in quartz formed at >400 °C. Ti concentrations in most rutile-bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of <750 °C using the TitaniQ geothermometer. Titanium concentrations of <10 ppm in all veins that formed at temperatures <350 °C suggest a broad correlation between Ti concentrations and temperature of quartz precipitation.

In quartz from most deposits formed at <350 °C, bimodal Al concentrations exist wherein some growth bands contain <50 ppm and others contain >2000 ppm, but in high-temperature quartz, Al concentrations are consistently in the range of several hundred ppm. Aluminum concentrations in quartz reflect the Al solubility in hydrothermal fluids, which is strongly dependent on pH. Aluminum concentrations in quartz therefore reflect fluctuations in pH that may drive metal-sulfide precipitation in hydrothermal systems.

Item ID: 9035
Item Type: Article (Research - C1)
ISSN: 1943-2682
Keywords: quartz; cathodoluminescence; hyrdothermal; microprobe; vein; trace elements
Date Deposited: 09 Mar 2010 05:18
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840199 Mineral Exploration not elsewhere classified @ 100%
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