Meridian Mining UK Societas, through its Brazilian subsidiary Rio Cabaçal Mineração Ltda., has an option agreement over the Project with two private Brazilian companies: Prometálica Mineração Ltda and IMS Engenharia Mineral Ltda.
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Summary:
Mineral Deposit
The metallogeny of Zn, Cu, Pb, Au and Ag mineralization in the Jaurú Belt is classified as a volcanogenic massive sulphide (VMS) mineral system developed within a Proterozoic Greenstone Sequence. Initially, felsic marine volcanism was followed by a deposition of sulphide minerals. Chert and sediment layers were deposited during the period of sulphide deposition. The final event was a period of intermediate volcanism.
In a typical volcanogenic massive sulphide deposit, the massive sulphides lie above stringer and stockwork mineralization associated with an alteration pipe. The top contact is usually very abrupt, and zinc tends to be concentrated close to this upper contact. Massive sulphide mineralization is usually capped by chert or silicified tuff overlain by weakly altered barren strata. Elements of the model for a classic VMS mineralization setting include a stratiform lens of massive sulphide overlying a discordant stringer sulphide zone within an envelope of altered rock (alteration pipe).
VMS deposits have a continuum of compositions through to gold-rich end members (Dubé et al, 2005), where gold contents in g/t can exceed combined percentage levels of Cu, Pb, and Zn. Such gold-rich deposits occur in a variety of submarine volcanic terranes from mafic bimodal through felsic bimodal to bimodal siliciclastic. Their host strata are commonly underlain by coeval subvolcanic intrusions and sill-dyke complexes, typically metamorphosed to greenschist and lower amphibolite facies in greenstone belts of various ages. The gold most commonly has an uneven distribution within the deposit due to both primary depositional controls and subsequent tectonic remobilization. The gold metal association varies from Cu dominant through to Zn-Pb dominant end members. They contain similar architectural elements to classic VMS deposits.
Mineralization Style
The mineralization host units are volcanic, volcanoclastic, and sedimentary rocks deposited in a marine environment. These units were cut by basic granitic and plutonic rocks. All are intensely metamorphosed and deformed, with folding and local faulting.
The Cu-Au-Ag mineralization zone has overall dimensions of 650m (down-dip) by 2,350m (along strike). The mineral zone strikes approximately 135°, dips at 10-20° to the southwest, and has a shallow plunge to the southeast of 10-20°. At lower grades, the mineralization has good continuity. Higher grade copper-gold trends are enveloped within the lower grade halo. The mineralization has a vertical elevation extent of approximately 200m, The true width is the mineral zone is typically some tens of metres (approximately 10 to 90m).
There are a range of mineral styles typical of a VMS deposit including massive sulphide, breccia zones with sulphide clasts and/or matrix, sulphide stringer zones and disseminated sulphides. One of the most important styles for gold mineralization involves later stage gold event superimposed on the original VMS stratigraphy. Examples are seen that include gold-rich quartz-sulphide veins, free gold developed within foliation, and gold-only layers in chloritic alteration zones detached from the VMS mineralization envelope. In addition to the drill core, good examples of the mineralization style are illustrated in photos from the Cabaçal Mine operations.
Mineral species at the Cabaçal mine consist of pyrite, chalcopyrite, pyrrhotite, sphalerite, galena, gold along with bismuth, selenium, and tellurium alloys.
In the uppermost part of the Cabaçal deposit, the mineralization has been oxidised. Erosion has caused the removal from of the upper clay saprolite for most areas such that depth to fresh rock can be quite shallow typically between 5 and 20m averaging 1-15m below surface.
Significant Mineralized Zones at Cabaçal
Mineralization at Cabaçal is related to three hydrothermal centres (Central, East and South Copper Zones). The main gold zone is a flat stringer zone related to the South Copper Zone (SCZ). In the Central Copper Zone (CCZ), past mining targeted high-grade gold in the core of an intense hydrothermal alteration pipe (ZCl) and, to a much lesser extent, the massive sulphide lenses. The East Copper Zone (ECZ) is a centre of lesser expression of vein-type copper mineralization, with erratic gold mineralization of the high-grade stringer type.
The large tonalite intrusion that is developed to the west of the Cabaçal deposit is likely to be a subvolcanic intrusion, providing a heat engine for convection of hydrothermal fluids.
The Cu-Au-Ag mineralization zone has overall dimensions of 650m (down-dip) by 2,350m (along strike). The mineral zone strikes approximately 135°, dips at 10-20° to the southwest, and has a shallow plunge to the southeast of 10-20°. At lower grades, the mineralization has good continuity with shorter-ranged higher grade copper-gold trends enveloped by the lower grade halo. The mineralisation outcrops and has reaches a vertical depth of 200m below surface. The true width of the mineral zone is variable ranging from 10 to 90m.