DBPapers
DOI: 10.5593/SGEM2015/B11/S1.055

RELATIONSHIPS BETWEEN CRUSTAL FAULTS, SHALLOW MAGMATIC CHAMBER AND NEOGENE PORPHYRY CU-AU SYSTEMS

I. Berbeleac, M. Nutu-Dragomir , F. Chitea
Tuesday 4 August 2015 by Libadmin2015

References: 15th International Multidisciplinary Scientific GeoConference SGEM 2015, www.sgem.org, SGEM2015 Conference Proceedings, ISBN 978-619-7105-31-5 / ISSN 1314-2704, June 18-24, 2015, Book1 Vol. 1, 435-442 pp

ABSTRACT
The Voia area is situated in the southern part of Golden Quadrilateral, Metaliferi Mountains (Romania). In a very narrow area ( 1km2) a set of three crustal faults (two oriented E-W and one NE-SW) have been identified by means of deep magnetotellurical sounding (EMS) data, partially checked with 18 exploration diamond drillings. These faults were major migration channels for Neogene magmas and related fluids rich in Cu, Au, Ag, Pb and Zn. The E to V-vergent faults are the hosts of three low-grade porphyry epithermal Cu-Au and epi- mesothermal Au-Ag, Pb, Zn, Cu systems. These systems are superimposed on a complex and poly-stage hornblende±biotite quartz andesite-quartz porphyry microdiorite intrusions, probably Sarmatian in age (12-11 My). According to exploration drillings the porphyry Cu-Au systems are developed below -150 to -300 m (below sea level) (<0.1 %Cu) depth and probably, continues under 1200 m depth (0.5– 0.6 %Cu, 0.6 g/t Au) as observed from mineralogical data of the deepest drilling (e. g. no 19). The shape of these intrusions is stocks-like with large lateral extents. The high sulfidation (HS) alteration is presents until 700-800m down where, the dominant veins mineral assemblage (pyrite-marcasite-gypsum-clay minerals ± chalcopyrite, magnetite, base metal sulfides) gradually superposed with probably younger low sulfidation (LS) mineral assemblage (native gold-base metal sulfides-carbonates-quartz ± anhydrite) (e.g. drilling no 17, vein m. -964 to -964.30 m = 87 g/t Au, this means 306 m below the sea level. The porphyry system gold is associated with chalcopyrite. The andesitic-microdioritic intrusions have deeply roots extending till 2-2.5 km in the upper parts of a mini-shallow magmatic chambers. The sizes and forms of these magmatic chambers have been especially influenced by the old thrusting planes, fact that explain their overlap and poly-stage evolution.

Keywords: Crustal faults, Shallow Magmatic Chamber, Neogene mineralizations, Voia, Metaliferi Mountains.

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