Vista Alegre, Rio Grande do Sul, Brazili

Regional Level Types
Vista Alegre	Municipality
Rio Grande do Sul	State
Brazil	Country

Paraná-Etendeka traps (Paraná & Etendeka igneous province)

The Vista Alegre district basalts contains labradorite, (55–70%), clinopyroxene (25–35%), augite and minor pigeonite, magnetite + ilmenite
(5–10%), plus small volumes of highly altered olivine; apatite is the principal trace accessory mineral. Most lavas are aphyric but sparse plagioclase and clinopyroxene phenocrysts occurs.
Abundant native copper occurs in the amygdaloidal upper crusts of the lavas. The amygdaloidal lavas have well-preserved clinopyroxene (augite) and
plagioclase phenocrysts. Quartz and calcite are common in all alteration stages throughout the district as vein fillings, fillings of amygdules, and replacements of other minerals. In relation to copper, they are more abundant from the middle to the end of the ore-forming process, e.g. quartz–calcite veins with native copper. Quartz is not present in amygdules with native copper, whereas calcite is found dominantly as post-zeolite deposition infillings of amygdules. Native copper has various shapes in the Vista Alegre district. Small, rare voids in the groundmass of massive lava cores are filled with native copper with dendritic shape. Also is disseminated in the upper crust of amygdaloidal lavas, fills amygdules , and is present in quartz veinlets. Amygdule filling generated the well-known large (1–50 cm in diameter, up to 50 kg) balls of native copper, found historically by farmers in the region. Native copper is often associated with clay minerals, zeolite, quartz, and calcite. In the upper crust, it is additionally associated with green chrysocolla.

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Vista_Alegre,_Rio_Grande_do_Sul
Wikidata ID:	Q1774451

Other Regions, Features and Areas containing this locality

References