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High-sulfidation epithermal Au and porphyry Cu-Au mineralization at the Karaayi target, Biga Peninsula, northwestern Turkey

Moira T. Smith, William A. Lepore, Tolga Incekaraoglu, Hakan Boran, April Barrios, Graham Leroux, Katherina Ross, Alper Buyuksolak, Ali Sevimli and Ken Raabe
High-sulfidation epithermal Au and porphyry Cu-Au mineralization at the Karaayi target, Biga Peninsula, northwestern Turkey (in Tectonics and metallogeny of the Tethyan orogenic belt, Jeremy P. Richards (editor))
Special Publication (Society of Economic Geologists (U. S.)) (2016) 19: 85-112


The Biga Peninsula in northwestern Turkey hosts a large number of high- and low-sulfidation epithermal gold-silver-(copper) and associated copper-gold porphyry deposits and prospects, associated with voluminous, Eocene-Miocene calc-alkaline volcanism and plutonism. In this area, 50 to 20 Ma intermediate to felsic volcanic and volcaniclastic strata overlie metamorphosed basement rocks of the Camlca Group. The volcanic sequence is variably altered over an area covering several hundreds of square kilometers, including argillic, advanced argillic, and massive to vuggy residual quartz alteration, the latter present at the tops of many of the higher elevation peaks in the area. Moderate- and high-angle normal and oblique faults are common in the area and influenced the distribution of mineralization. While gold mineralization associated with these high-sulfidation epithermal systems and flanking low-sulfidation epithermal systems has long been recognized, the existence of porphyry roots to these systems was not fully appreciated until the discovery of the Halilag a porphyry in 2008. In the southern part of the TV Tower property, low relief areas consist of schist and serpentinite intruded by the Kuscayir pluton, a composite, approximately 40 Ma intrusion that averages granodiorite in composition. Intermediate volcanic and volcaniclastic rocks are exposed in the highest elevation areas. The northern edge of the pluton, at low to intermediate elevations, consists of at least six intrusions of similar age and composition that differ primarily in degree of porphyritic texture and phenocryst quartz content. The intrusions are parsed into pre- syn- and late mineralization phases with respect to hydrothermal alteration and mineralization related to at least two Au-Cu porphyry centers, Valley and Hilltop. The porphyry systems occur below and are to some degree overprinted by high-sulfidation alteration and mineralization. The porphyry/high-sulfidation system was subjected to weathering and oxidation, giving rise to a supergene copper enrichment blanket that lies near the transition from the high sulfidation into the porphyry environment. Alteration associated with the porphyry systems includes chlorite-magnetite-actinolite, K-feldspar-biotitequartz-magnetite-hematite ("potassic"), and, at higher elevations, overprinting quartz-muscovite ("phyllic") alteration. Quartz stockwork veining is ubiquitous in the phyllic and potassic assemblages, and includes quartz-K-feldspar "A" veins, quartz sulfide "B" veins, pyrite-quartz "D" veins, and quartz-magnetite "M" veins. Copper mineral assemblages range from bornite-chalcopyrite to chalcopyrite-pyrite, and chalcopyrite-chalcocite or chalcocite-covellite-digenite in the supergene zones. High-sulfidation epithermal mineralization is dominantly oxidized, and consists of residual vuggy and massive quartz, alunite, pyrophyllite, and iron oxides. New U-Pb dates for the Kuscayir pluton and Hilltop and Valley intrusions range from 38 to 40 Ma, consistent with other Cu-Au porphyry systems in the region, whereas most dated high-sulfidation epithermal deposits in the region formed at roughly 29 Ma, coeval with an Oligocene suite of intrusions. It is possible that the epithermal-porphyry relationship at Karaayi is one of overprinting of two unrelated hydrothermal systems.

ISSN: 1547-3112
Serial Title: Special Publication (Society of Economic Geologists (U. S.))
Serial Volume: 19
Title: High-sulfidation epithermal Au and porphyry Cu-Au mineralization at the Karaayi target, Biga Peninsula, northwestern Turkey
Title: Tectonics and metallogeny of the Tethyan orogenic belt
Affiliation: Pilot Gold, Vancouver, BC, Canada
Affiliation: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Pages: 85-112
Published: 2016
Text Language: English
Publisher: Society of Economic Geologists, Littleton, CO, United States
References: 46
Accession Number: 2018-013075
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
N40°13'41" - N40°13'41", E27°14'32" - E27°14'32"
Secondary Affiliation: University of British Columbia, CAN, CanadaPanterra Geoservices, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 201803
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