| Reference Type | Journal (article/letter/editorial) |
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| Title | Microtextural evidence for the recrystallization of opal-A to quartz in epithermal veins: A case study from the McLaughlin deposit, California |
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| Journal | Ore Geology Reviews |
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| Authors | Gissler, Garrett D. | Author |
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| Monecke, Thomas | Author |
| Reynolds, T. James | Author |
| Guzman, Mario A. | Author |
| Ellison, Eric T. | Author |
| Sherlock, Ross | Author |
| Year | 2024 | Volume | < 169 > |
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| URL | |
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| DOI | doi:10.1016/j.oregeorev.2024.106105Search in ResearchGate |
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| Generate Citation Formats |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 17424063 | Long-form Identifier | mindat:1:5:17424063:3 |
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| GUID | 0 |
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| Full Reference | Gissler, Garrett D., Monecke, Thomas, Reynolds, T. James, Guzman, Mario A., Ellison, Eric T., Sherlock, Ross (2024) Microtextural evidence for the recrystallization of opal-A to quartz in epithermal veins: A case study from the McLaughlin deposit, California. Ore Geology Reviews, 169. 106105 doi:10.1016/j.oregeorev.2024.106105 |
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| Plain Text | Gissler, Garrett D., Monecke, Thomas, Reynolds, T. James, Guzman, Mario A., Ellison, Eric T., Sherlock, Ross (2024) Microtextural evidence for the recrystallization of opal-A to quartz in epithermal veins: A case study from the McLaughlin deposit, California. Ore Geology Reviews, 169. 106105 doi:10.1016/j.oregeorev.2024.106105 |
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| In | Link this record to the correct parent record (if possible) |
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| Abstract/Notes | High-grade ores in low-sulfidation epithermal deposits commonly consist of banded veins containing quartz as the most abundant gangue mineral. Previous studies suggested that at least some of the quartz has formed as a product of recrystallization from a noncrystalline silica precursor. Detailed petrographic studies confirm that high-grade veins from the <2.2 Ma McLaughlin deposit in California were originally entirely composed of opal-AG. The noncrystalline silica is isotropic in crossed-polarized light and consists of compacted microspheres that are up to several micrometers in size. In many bands of the high-grade veins, the thermodynamically unstable opal-AG has matured to quartz. The recrystallization of the noncrystalline silica resulted in the development of quartz and ore textures that mask the original conditions of vein formation. Incipient recrystallization of the opal-AG caused the formation of lepispheres consisting of opal-CT as well as the development of concentrically banded silica spheres. Continued maturation led to the growth of elongated quartz crystals or complexly shaped quartz aggregates in the cores of the concentrically banded silica spheres. Amalgamation of quartz crystals caused the development of mosaic quartz or flamboyant quartz. Ripening produced large prismatic quartz crystals, which are characterized by zones of feathery appearance. Fluid inclusions within the quartz formed through recrystallization are typically highly irregular in shape and show inconsistent liquid-to-vapor volumetric proportions, but assemblages with consistent ratios are also present. Bands rich in fluid inclusions occurring along former recrystallization fronts in prismatic quartz crystals resemble growth zones in zonal quartz. Recrystallization of the silica matrix resulted in grain coarsening of the ore minerals and encapsulation of ore minerals by quartz. In areas where recrystallization of the noncrystalline silica proceeded to completeness, the quartz textures could be easily misinterpreted to indicate that quartz growth occurred in open space with the ore minerals infilling vug spaces. Correct recognition of recrystallization textures has significant implications for paragenetic investigations on vein material from epithermal deposits as well as the design of fluid inclusion studies. |
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