Abstract

The Madeleine copper deposit is hosted by biotite hornfels adjacent to the McGerrigle granitic complex, Quebec, and consists of stockwork orebodies, outwardly zoned from bornite-chalcopyrite to chalcopyrite-pyrrhotite. The mineralization predated the peak of contact metamorphism and is associated with biotite and calc-silicate vein and alteration assemblages. Chlorite-muscovite alteration and quartz-carbonate veins postdated mineralization.Vein quartz contains low- and high-salinity aqueous and CO 2 - CH 4 aqueous and nonaqueous fluid inclusion types. Isochore projections suggest that the deposit formed at 400 degrees to 600 degrees C and 1 to 2 kbars. Low ice-melting and eutectic temperatures indicate that some aqueous inclusions have high calcium contents.A model has been developed for the fluid evolution in which interaction of high-salinity orthomagmatic fluids with organic-rich shales produced CH 4 /N 2 -rich fluids and caused biotite alteration. Locally, the orthomagmatic fluids interacted with calcareous beds, releasing CO 2 and increasing their calcium content. The latter subsequently caused calc-silicate alteration. Chlorite-muscovite alteration and quartz-carbonate veining were caused by lower salinity fluids derived largely from formational waters. Outwardly decreasing water/rock ratios, which produced corresponding decreases in temperature and/or Cu/Fe and/or increases in a (sub H 2 S) , are invoked to explain the observed zonation in sulfide mineralogy.

First Page Preview

First page PDF preview
You do not currently have access to this article.