Reference Type | Journal (article/letter/editorial) |
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Title | Late-kinematic gold mineralisation during regional uplift and the role of nitrogen: an example from the La Codosera area, W. Spain |
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Journal | Mineralogical Magazine | ISSN | 0026-461X |
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Authors | Dee, S. J. | Author |
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Roberts, S. | Author |
Year | 1993 (September) | Volume | 57 |
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Issue | 388 |
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Publisher | Mineralogical Society |
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Download URL | https://rruff.info/doclib/MinMag/Volume_57/57-388-437.pdf+ |
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DOI | doi:10.1180/minmag.1993.057.388.07Search in ResearchGate |
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| Generate Citation Formats |
Mindat Ref. ID | 1939 | Long-form Identifier | mindat:1:5:1939:6 |
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GUID | 0 |
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Full Reference | Dee, S. J., Roberts, S. (1993) Late-kinematic gold mineralisation during regional uplift and the role of nitrogen: an example from the La Codosera area, W. Spain. Mineralogical Magazine, 57 (388) 437-450 doi:10.1180/minmag.1993.057.388.07 |
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Plain Text | Dee, S. J., Roberts, S. (1993) Late-kinematic gold mineralisation during regional uplift and the role of nitrogen: an example from the La Codosera area, W. Spain. Mineralogical Magazine, 57 (388) 437-450 doi:10.1180/minmag.1993.057.388.07 |
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In | (1993, September) Mineralogical Magazine Vol. 57 (388) Mineralogical Society |
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Abstract/Notes | AbstractVein formation occurred throughout a deformation sequence which involved early transpressive ductile deformation through to late-kinematic transpressive brittle structures which host a series of gold prospects. Fluid inclusion data from (S1) fabric parallel veins associated with early deformation suggest that a low-salinity aqueous fluid, with a mean salinity of 6.4 wt.%, was present during peak metamorphism, Pelite mineralogy and isochores constrain peak metamorphism to the lowermost part of the upper greenschist facies at 325 to 425°C and 1.4 to 3.4 kbar.Fluid inclusion data from auriferous and barren late-kinematic quartz veins, both containing unmixing assemblages of aqueo-carbonic inclusions with low salinities of ≈2.7 wt.% NaCl equiv., indicate unmixing occurred at 300°C and 1.5 kbar.Volatiles (CO2, N2, CH4) are observed in all the late-kinematic veins. The N2 contents of veins with elevated gold grades are typically higher than those with low gold grades. N2 reaches 8.7 mole% in a vein with 0.49−4.6 p.p.m. Au compared to <1 mole% in a vein with <0.05 p.p.m. Au. The CH4 content of late kinematic veins is generally less than 1 mole% and shows no relative enrichment in mineralised veins. The generation of N2 in the mineralising fluid most likely results from interaction of fluid with the ammonium ion, NH4+, in micas and feldspars. This interaction could take place either at source, due to metamorphic devolatisation reactions, or along those structures which acted as fluid conduits due to fluid-rock interaction. |
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