Browsing by Author "Lord, Richard A."

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Geological and Mineralization Characteristics of the Kestanelik Epithermal Au-Ag Deposit in the Tethyan Metallogenic Belt, Nw Turkey
(Geological Society Korea, 2020) Gulyuz, Nilay; Gulyuz, Erhan; Shipton, Zoe K.; Kuscu, Ilkay; Lord, Richard A.
Kestanelik epithermal gold deposit is situated in the Biga Peninsula, which hosts numerous metallic deposits belonging to the Tethyan Metallogenic Belt. In the Biga peninsula the Tethyan Metallogenic Belt is represented by a Neo-Tethyan suture zone. Discovered deposits along the belt are commonly associated with Cenozoic magmatism ranging between 52 and 18 Ma in age, formed due syn- to post-collisional tectonics. In this study, we focus on the deposit-scale geological and mineralization characteristics of Kestanelik in order to determine the formation and evolution of the deposit within the tectono-magmatic history of the Biga Peninsula. We (1) mapped the geology of the deposit area (2) conducted paleostress analyses, (3) observed and examined the macroscopic and petrographical textural, mineralogical and alteration characteristics of the mineralization and (4) interpreted geophysical resistivity survey and geochemical assay data. The stratigraphic age of the Kestanelik deposit, bracketed by cross cutting relations and supported by the geophysical data, is middle Lutetian-early Priabonian which also implies that the deposit has a genetic link with the Cenozoic post-collisional calc-alkaline magmatism. A NE-SW oriented compressional regime determined from the paleostress analyses is consistent with the kinematics of the vein system and is attributed to the collision and further convergence after the closure of the northern branch of the Neo-Tethys Ocean. The fracture system provided structural pathways for the transport of the hydrothermal fluids. The common presence of pseudo-bladed quartz and hydrothermal breccias, and the low total sulphide and base metal contents in the mineralized veins indicate that the Kestanelik is a low sulphidation epithermal-type gold deposit. Boiling, mixing (hypogene oxidation) and supergene enrichment are the likely gold deposition and enrichment processes respectively.
Repeated Reactivation of Clogged Permeable Pathways in Epithermal Gold Deposits: Kestanelik Epithermal Vein System, Nw Turkey
(Geological Soc Publ House, 2018) Gulyuz, Nilay; Shipton, Zoe K.; Kuscu, Ilkay; Lord, Richard A.; Kaymakci, Nuretdin; Gulyuz, Erhan; Gladwell, David R.
This study presents a detailed study of the dimensions, geometry, textures and breccias of a well-exposed epithermal vein system, the Kestanelik gold deposit in the Biga Peninsula, NW Turkey, and investigates the permeability enhancement mechanisms in epithermal gold deposits. Here mineralization is associated with quartz veins up to 13.6 m thick. Vein textures and breccia components indicate repeated sealing and subsequent brecciation of wall rock and pre-existing vein infill. Field and petrographic analyses characterize east-west-trending veins as left lateral faults, whereas NE-SW-trending veins are extensional (Mode I) fractures. Cataclasite and tectonic breccia of wall rocks and early quartz, hydrothermal crackle breccias, and matrix-supported chaotic breccias of pre-existing vein infill, all of which are cemented by late iron-oxide-bearing quartz, indicate that co-seismic rupturing and hydraulic fracturing are two major permeability enhancement mechanisms. In addition, transient variations in local stress direction, caused by syn-mineralization dyke intrusion, may have enhanced permeability on misoriented surfaces and at locations where the dip changes. This study emphasizes the importance of understanding structural geology and kinematics as controls on the location of boiling and mineralization mechanisms in epithermal gold deposits.