Browsing by Author "Arehart, Greg B."

Now showing 1 - 3 of 3

Geology and Isotope Geochemistry (c-O of the Diyadin Gold Deposit, Eastern Turkey: a Newly-Discovered Carlin-Like Deposit
(Elsevier Science Bv, 2011) Colakoglu, Ali Riza; Oruc, Mahmut; Arehart, Greg B.; Poulson, Simon
Diyadin mineralization is the first reported gold deposit located in a collisional tectonic environment in Eastern Anatolia. The mineralization is related to N-S and N10-20 degrees W-trending fault systems and hosted within the Paleozoic metamorphic basement rocks of the Anatolide-Toride microcontinent. Calc-schist, dolomitic marble and Miocene and Quaternary volcanic rocks comprise the exposed units in the mineralized area. Geochemical signatures, alteration types and host rock characteristics of the Diyadin gold deposit resemble those of Carlin-type deposits. Mineralization is constrained by alteration of overlying volcanic rocks to younger than similar to 14 Ma (K-Ar). Carbon and oxygen stable isotope measurements of carbonate rocks were made on six drill holes (n = 81) with an additional four samples of fresh carbonate rocks from surface outcrops. Background carbonate rocks have delta C-13(V-PDB) similar to 1.8 parts per thousand. and delta O-18(V-SMOW) similar to 27 parts per thousand. Isotopically-altered host rock samples have decreased delta O-18 (down to similar to+11.4 parts per thousand) and variable delta C-13 (from -3.6 to +4.8 parts per thousand). Postore carbonate veins and cave-fill material have distinctly different isotopic signatures, particularly carbon (from delta C-13 = +8.4 to +9.8 parts per thousand). Whether this post-ore carbonate is simply very late in mineralization associated with the gold system, or is a completely different, younger system utilizing the same pathways, is unclear at present. Within the host rock sample set, there is no correlation between gold and delta C-13, and a weak correlation between gold and delta O-18, indicative of water-rock interaction and isotopic alteration. Both the isotopic data and structural mapping suggest that the main upflow zone for the deposit is near the northern portion of the drill fence. Additional data at multiple scales are required to clarify the relationship(s) between fluid flow and mineralization. (C) 2011 Elsevier B.V. All rights reserved.
Low-Sulfidation Type Au-Ag Mineralization at Bergama, Izmir, Turkey
(Elsevier, 2007) Yilmaz, Huseyin; Oyman, Tolga; Arehart, Greg B.; Colakoglu, A. Riza; Billor, Zeki
Bergama, the center of Bergarna County, is located in western Turkey and includes the villages of Ovacik, Narlica and Saganci. The Ovacik epitherinal gold-silver deposit is located in the Western Anatolian Volcanic and Extensional Province, adjacent to the ENE-trending Bergama graben, some 100 kin north of the city of Izmir. Gold of economic grades at the Ovacik deposit (reserves 4.19 Mt at 7.6 g/t) occurs in epithermal quartz veins which display low-temperature epithermal textures, including crustiform banding, quartz pseudomorphs after bladed calcite, and multiphase hydrothermal breccias. Alteration minerals at both Ovacik and Narlica are dominated by smectite, mixed-layer illite/smectite, chalcedonic quartz and adularia, whereas major kaolinite and minor inixed-layer smectite/illite (> 13.4 angstrom) occur at Saganci. The total sulfide content at Ovacik is low (< 2%) and is dominated by pyrite with traces of electrum, chalcopyrite, arsenopyrite, acanthite, tetrahedrite, pyrargyrite, stibmte, galena, chalcocite, bomite, covellite and sphalerite, occurring mainly within breccia clasts. Pyrite and mareasite appear to be the most common opaque minerals at Narlica and form dark sulfide-rich bands along with traces of electrum, native silver and chalcopyrite; pyrite is the only sulfide identified at Saganci. 40Ar/39Ar dating of adularia from gold-bearing quartz veins indicates an age of mineralization of about 18.2 +/- 0.2 Ma. Fluid inclusion studies at Ovacik reveal that main-stage quartz contains predominantly liquid-rich inclusions with homogenization temperatures (T-h) ranging from 150 to 305 degrees C, with the majority of T-h, varying between 165 to 205 degrees C: ice-melting temperatures (T-h) ranging from - 0.4 to - 1.2 degrees C (salinity < 2 wt.% NaCl equiv.) are dominant. Higher T-h, (220 to 248 degrees C) at the Narlica deposit may be attributed to the deeper level of exposure. Bergama, the center of Bergarna County, is located in western Turkey and includes the villages of Ovacik, Narlica and Saganci. The Ovacik epitherinal gold-silver deposit is located in the Western Anatolian Volcanic and Extensional Province, adjacent to the ENE-trending Bergama graben, some 100 kin north of the city of Izmir. Gold of economic grades at the Ovacik deposit (reserves 4.19 Mt at 7.6 g/t) occurs in epithermal quartz veins which display low-temperature epithermal textures, including crustiform banding, quartz pseudomorphs after bladed calcite, and multiphase hydrothermal breccias. Alteration minerals at both Ovacik and Narlica are dominated by smectite, mixed-layer illite/smectite, chalcedonic quartz and adularia, whereas major kaolinite and minor inixed-layer smectite/illite (> 13.4 angstrom) occur at Saganci. The total sulfide content at Ovacik is low (< 2%) and is dominated by pyrite with traces of electrum, chalcopyrite, arsenopyrite, acanthite, tetrahedrite, pyrargyrite, stibmte, galena, chalcocite, bomite, covellite and sphalerite, occurring mainly within breccia clasts. Pyrite and mareasite appear to be the most common opaque minerals at Narlica and form dark sulfide-rich bands along with traces of electrum, native silver and chalcopyrite; pyrite is the only sulfide identified at Saganci. 40Ar/39Ar dating of adularia from gold-bearing quartz veins indicates an age of mineralization of about 18.2 +/- 0.2 Ma. Fluid inclusion studies at Ovacik reveal that main-stage quartz contains predominantly liquid-rich inclusions with homogenization temperatures (T-h) ranging from 150 to 305 degrees C, with the majority of T-h, varying between 165 to 205 degrees C: ice-melting temperatures (T-h) ranging from - 0.4 to - 1.2 degrees C (salinity < 2 wt.% NaCl equiv.) are dominant. Higher T-h, (220 to 248 degrees C) at the Narlica deposit may be attributed to the deeper level of exposure. Bergama, the center of Bergarna County, is located in western Turkey and includes the villages of Ovacik, Narlica and Saganci. The Ovacik epitherinal gold-silver deposit is located in the Western Anatolian Volcanic and Extensional Province, adjacent to the ENE-trending Bergama graben, some 100 kin north of the city of Izmir. Gold of economic grades at the Ovacik deposit (reserves 4.19 Mt at 7.6 g/t) occurs in epithermal quartz veins which display low-temperature epithermal textures, including crustiform banding, quartz pseudomorphs after bladed calcite, and multiphase hydrothermal breccias. Alteration minerals at both Ovacik and Narlica are dominated by smectite, mixed-layer illite/smectite, chalcedonic quartz and adularia, whereas major kaolinite and minor inixed-layer smectite/illite (> 13.4 angstrom) occur at Saganci. The total sulfide content at Ovacik is low (< 2%) and is dominated by pyrite with traces of electrum, chalcopyrite, arsenopyrite, acanthite, tetrahedrite, pyrargyrite, stibmte, galena, chalcocite, bomite, covellite and sphalerite, occurring mainly within breccia clasts. Pyrite and mareasite appear to be the most common opaque minerals at Narlica and form dark sulfide-rich bands along with traces of electrum, native silver and chalcopyrite; pyrite is the only sulfide identified at Saganci. 40Ar/39Ar dating of adularia from gold-bearing quartz veins indicates an age of mineralization of about 18.2 +/- 0.2 Ma. Fluid inclusion studies at Ovacik reveal that main-stage quartz contains predominantly liquid-rich inclusions with homogenization temperatures (T-h) ranging from 150 to 305 degrees C, with the majority of T-h, varying between 165 to 205 degrees C: ice-melting temperatures (T-h) ranging from - 0.4 to - 1.2 degrees C (salinity < 2 wt.% NaCl equiv.) are dominant. Higher T-h, (220 to 248 degrees C) at the Narlica deposit may be attributed to the deeper level of exposure.
The Petrogenesis of Saricimen (caldiran-Van) Quartz Monzodiorite: Implication for Initiation of Magmatism (Late Medial Miocene) in the East Anatolian Collision Zone, Turkey
(Elsevier, 2010) Colakoglu, Ali Riza; Arehart, Greg B.
The Saricimen porphyry is exposed as a sub-volcanic pluton within the Upper Cretaceous ophiolitic rocks in East Anatolian Accretionary Complex. The pluton is quartz monzodioritic in composition consisting of feldspar, hornblende, and biotite phenocrysts set in a fine-grained matrix. Major element geochemistry indicates the pluton is of high-K, calc-alkaline, metaluminous character, with a low (0.81-0.90) Aluminum Saturation Index (ASI). Trace element and sulfur isotope geochemistry suggests that the Sancimen porphyry was mantle-derived and contaminated by crustal materials during ascent. Tectonically, this and related volcanic and plutonic rocks in eastern Turkey and Iran are subduction-related and comprise the earliest documented neotectonic igneous activity associated with the final closure of the neo-Tethys between the Arabian and Eurasia plates at similar to 14-13 Ma. (C) 2010 Elsevier B.V. All rights reserved.