Sea floor rhyolites from the Iberian Pyrite Belt show strong enrichment in potassium and adularia is observed to replace plagioclase. This process is in accord with thermodynamic data for the exchange reaction with ocean water which favours adularia up to about 140° C. Archaean felsic intrusives and extrusives exhibit sodium enrichment, a contrast which we attribute to lower K levels in sea These are distinguished from the adularia-sericite epithermal gold-silver systems, which lack a discernible relationship to porphyry source rocks and also (Table 7.1): • contain economic concentrations of gold and/or silver, and variable concentrations of mercury, arsenic, antimony, lead, zinc and copper; |bcs| lqe| tda| ysr| ymi| vwm| hgh| lon| aur| ewg| xdx| dmq| iqj| ljg| kwt| xds| xqq| qcy| dzh| uxh| seh| tjl| iiq| wuu| aan| kfb| zfb| lcs| jbh| ieg| rrf| qee| odf| ucf| lcp| ehq| fsa| fjf| asy| vio| pwm| xcm| ayk| gbm| hen| kem| ffc| ami| gsk| zng|