Deseado Massif
Tags: andesite conglomerate cretaceous limestone lower cretaceous middle jurassic permian rhyolite sandstone shale triassic tuff upper jurassic
Description:
Santa Cruz Province, Argentina. The Deseado Massif consists of Paleozoic metamorphic basement unconformably overlain by Middle to Upper Jurassic bimodal andesitic and rhyolitic volcanics and volcaniclastics. Cretaceous sediments and Tertiary to Quaternary basalts overlie the Jurassic volcanics.
Jurassic magmatism in the Deseado Massif accompanied extensional tectonics marked by normal faults, horst and graben formation, and block tilting during the opening of the southern Atlantic Ocean. Several small basins formed after the main volcanic episodes, a consequence of intense diastrophic block faulting. Continental sediments were deposited in the Upper Jurassic to Lower Cretaceous in those basins, represented by tuffaceous sandstones, tuffites, limestones, conglomerates, and shales. Low sulphidation (“LS”) epithermal silver-gold deposits accompanied magmatism and deformation. Basaltic plateau volcanism was dominant during the Tertiary span, coupled with minor marine ingressions that produced the deposition of sandstones, shales and fossiliferous limestones. Intrusive rocks are scarce in the area. They are represented by irregular bodies of rhyolitic porphyries that intrude the main silicic volcanic units, and by basaltic plugs that pierce the whole sequence.
Large amounts of intermediate to silicic volcanics were erupted in the Jurassic, in a sub-aerial, cratonic back-arc tensional environment. These volcanics are subdivided into the Bajo Pobre Formation, predominantly of intermediate to basic composition, and the felsic Bahia Laura Group that discordantly overlies the Bajo Pobre Formation. The Bahia Laura Group is further subdivided into the interdigitating Chon Aike Formation (dominantly ignimbrites) and the La Matilde Formation (dominantly volcaniclastics).
The volcanic rocks of the Deseado Massif host the producing silver-gold mines of Cerro Vanguardia, Marta Mine, Manantial Espejo and San José, as well as the prospects and development projects of Cerro Negro, Lomada de Leiva and La Josefina. The principal host rock for silver and gold mineralization in the San José district is the Bajo Pobre Formation where veins are typically developed in competent andesite flows, and to a lesser extent, in volcaniclastic units.
Geology of the Deseado Massif, Argentina:
Deposits
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Name: San Jose
Phase: Operations
Mine Type: Underground
Intro:
The San Jose silver-gold mine is located in Argentina, in the Santa Cruz province, 1,750 kilometres south-southwest of Buenos Aires. The property covers a total area of 50,491 hectares and consists of 46 contiguous mining concessions totalling 40,499 hectares and an exploration permit covering almost 10,000 hectares. The San Jose property is located approximately 20 kilometres north of Goldcorp’s Cerro Negro project.
Mineralizations
No mineralizations available.
Placers
No placers available.