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<front>
<journal-meta>
<journal-id journal-id-type="archive">gsminmag</journal-id>
<journal-title>Mineralogical Magazine</journal-title>
<abbrev-journal-title abbrev-type="full">Mineralogical Magazine</abbrev-journal-title>
<issn pub-type="ppub">0026-461X</issn>
<publisher>
<publisher-name>Mineralogical Society</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1180/minmag.1993.057.388.07</article-id>
<title-group>
<article-title>Late-Kinematic Gold Mineralisation During Regional Uplift and the Role of Nitrogen: An Example from the La Codosera Area, W. Spain</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Dee</surname>
<given-names>S. J.</given-names>
</name></contrib>
<contrib contrib-type="author">
<name>
<surname>Roberts</surname>
<given-names>S.</given-names>
</name></contrib>
<aff>Department of Geology, The University, Highfield, Southampton SO9 5NH, U.K.</aff></contrib-group>
<pub-date pub-type="ppub">
<month>9</month>
<year>1993</year>
</pub-date>
<volume>57</volume>
<issue>388</issue>
<fpage>437</fpage>
<lpage>450</lpage>
<history>
<date date-type="received">
<day>1</day>
<month>9</month>
<year>1992</year>
</date>
<date date-type="rev-recd">
<day>19</day>
<month>2</month>
<year>1993</year>
</date></history>
<copyright-statement>Copyright &#x00A9; 1993, The Mineralogical Society</copyright-statement>
<copyright-year>1993</copyright-year>
<abstract>
<title>Abstract</title>
<p>Vein 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&#x00B0;C and 1.4 to 3.4 kbar.</p>
<p>Fluid inclusion data from auriferous and barren late-kinematic quartz veins, both containing unmixing assemblages of aqueo-carbonic inclusions with low salinities of &#x2248;2.7 wt.% NaCl equiv., indicate unmixing occurred at 300&#x00B0;C and 1.5 kbar.</p>
<p>Volatiles (CO<sub>2</sub>, N<sub>2</sub>, CH<sub>4</sub>) are observed in all the late-kinematic veins. The N<sub>2</sub> contents of veins with elevated gold grades are typically higher than those with low gold grades. N<sub>2</sub> reaches 8.7 mole% in a vein with 0.49&#x2013;4.6 p.p.m. Au compared to &#x003C;1 mole% in a vein with &#x003C;0.05 p.p.m. Au. The CH<sub>4</sub> content of late kinematic veins is generally less than 1 mole% and shows no relative enrichment in mineralised veins. The generation of N<sub>2</sub> in the mineralising fluid most likely results from interaction of fluid with the ammonium ion, NH<sub>4</sub><sup>+</sup>, 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.</p></abstract>
<kwd-group>
<title>Keywords</title>
<kwd>gold mineralisation</kwd>
<kwd>nitrogen</kwd>
<kwd>Spain</kwd>
<kwd>fluid inclusions</kwd>
</kwd-group>
</article-meta>
</front>
</article>
