Rory R. McNab, Joël Brugger, C. Voisey, Andrew G. Tomkins
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引用次数: 0
Abstract
Hyperenrichment of Au in orogenic ores occurs overwhelmingly within quartz veins, but the formation pathway of quartz veins in orogenic systems remains enigmatic. We conducted hydrothermal experiments simulating coprecipitation of Au and amorphous silica and subsequent recrystallization to test whether this is a viable mechanism to generate Au nuggets within quartz veins. Within minutes, coprecipitation of amorphous silica and Au nanoparticles occurred, representing an effective Au deposition mechanism. Within one week, amorphous silica had recrystallized to quartz, causing the coarsening of Au particles and their relocation to quartz grain boundaries and fractures. The experimental textures are similar to those observed in high-grade zones of orogenic gold deposits. In addition to trapping Au, amorphous silica may increase competency contrasts that facilitate short-term fracture reactivation during earthquake aftershock periods or swarms, allowing further Au input from fresh fluids. These findings demonstrate that amorphous silica precipitation may be an important transient stage in orogenic gold deposit formation, with significant implications for metal accumulation in quartz veins.
期刊介绍:
Published since 1973, Geology features rapid publication of about 23 refereed short (four-page) papers each month. Articles cover all earth-science disciplines and include new investigations and provocative topics. Professional geologists and university-level students in the earth sciences use this widely read journal to keep up with scientific research trends. The online forum section facilitates author-reader dialog. Includes color and occasional large-format illustrations on oversized loose inserts.