Yazar "Banks, David A." seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim Yok
    Öğe
    Fluid evolution of mixed base-metal gold mineralization in the Tethys belt: Koru deposit, Turkey
    (SOC GEOLOGY APPLIED MINERAL DEPOSITS-SGA, 2017) Bozkaya, Gulcan; Bozkaya, Omer; Banks, David A.; Gokce, Ahmet; MercierLangevin, P; Dube, B; Bardoux, M; Ross, PS; Dion, C
    Koru is one of a number of base-metal gold deposits hosted by Oligo-Miocene volcano-sedimentary rocks of deposits in the Biga peninsula. Barite, quartz and galena are main minerals and are accompanied by minor amounts of sphalerite, pyrite, chalcopyrite, covellite and marcasite. Th of fluid inclusions indicates two distinct fluid pulses, one at high temperature (340 degrees C) commensurate with epithermal mineralization and boiling/near boiling conditions and the second approximately 150 degrees C lower. Salinity in both instances was from 11-0.2 wt. % NaCl. The range of temperatures within individual samples is consistent with variations from near lithostatic to hydrostatic pressure during vein and fracture opening. There are two different ranges of delta S-34 values of H2S in equilibrium with barite (+5.5 to +7.9 parts per thousand) and sulfide minerals (-2.1 to -0.5 parts per thousand), indicating that the sulfur in sulfide minerals and barite derived from different sources; magmatic and seawater respectively.
  • Küçük Resim Yok
    Öğe
    Fluid processes in the Tesbihdere base-metal-Au deposit: Implications for epithermal mineralization in the Biga Peninsula, NW Turkey
    (DE GRUYTER POLAND SP ZOO, 2014) Bozkaya, Gulcan; Banks, David A.; Ozbas, Fatih; Wallington, Jon
    Tesbihdere is one of a number of spatially close epithermal Cu-Pb-Zn-Ag-Au deposits hosted by andesites and rhyolites, typical of deposits in the Biga peninsula. Microthermometry of fluid inclusions shows a wide range of temperatures, similar to 360-170A degrees C, and salinities, similar to 10-0.5 wt.% NaCl, in the different deposits studied. Dilution of a moderately saline magmatic? fluid with meteoric water occurred at constant temperature indicating, the temperature of both fluids was controlled by the geological environment. Boiling was not a major factor, but did occur in very minor amounts. The large range of temperatures within individual samples can only reasonably be explained by variations from near lithostatic to hydrostatic pressure during vein and fracture opening. That this pressure decrease did not produce extensive boiling suggests that vein opening was gradual rather than aggressive, allowing the pressure and temperature decrease to follow a path close to the L-V boiling curve. P-T reconstruction places emplacement of these ore veins at between 300-500 m beneath the surface. Similarities of LA-ICPMS of fluid inclusions from Tesbihdere, Azitepe and Basmakci, supports the conclusion that they were part of the same contemporaneous mineralizing system. The fluids are dominated by Na, with the concentrations of K > Ca > Mg combined equivalent to the concentration of Na. The range of K/Na ratios is not consistent with the fluid inclusion temperatures as the calculated temperatures are significantly higher indicating the fluids were not close to equilibrium with the enclosing rocks. Elevated K concentrations are consistent with acid-sulphate waters in shallow epithermal systems. Ore metals Cu, Zn and Pb are present in significant concentrations similar to 500, 300 and 200 ppm respectively and the low Fe/Mn ratios are indicative of a relatively oxidising fluid. The negative delta S-34 values of sulphides are consistent with boiling and oxidising redox conditions.
  • Küçük Resim Yok
    Öğe
    P-T-X constraints on the Koru epithermal base-metal (± Au) deposit, Biga Peninsula, NW Turkey
    (Elsevier, 2020) Bozkaya, Gulcan; Bozkaya, Omer; Banks, David A.; Gokce, Ahmet
    The Koru deposit is a typical intermediate sulfidation base-metal (+/- Au) example of volcanic-volcaniclastic hosted mineralization in the Biga Peninsula and northwestern Turkey. Ore deposition was associated with the collisional and post-collisional tectonics related to the closure of the Tethys Ocean. Galena, baryte and quartz are main minerals, accompanied by minor amounts of sphalerite, pyrite, chalcopyrite, covellite and marcasite. The homogenization temperature of fluid inclusions indicates two distinct fluid pulses, one at a temperature commensurate with epithermal mineralization and boiling/near boiling conditions at c. 350 degrees C, with the second approximately 150-200 degrees C lower. Salinity in both instances was from 11.0 to 0.2 wt% NaCl. The dD and d18O values of water in equilibrium with early quartz and fluid inclusions plot close to the magmatic water box indicating the source of the high temperature fluid was magmatic. delta D and delta O-18 values from early and late baryte trend towards the meteoric water line (MWL), but this is not due to mixing with meteoric water, rather equilibration with alteration assemblages at decreasing temperature. LA-ICP-MS analyses of fluid inclusions reveal high Cu-Zn-Pb concentrations in the fluids, despite their low salinity, transported as chloride complexes. The range of temperatures within the early quartz and sphalerite mineralization can be explained by pressure variations during vein and fracture opening.
  • Küçük Resim Yok
    Öğe
    The origin, age and duration of hydrothermal alteration associated with iron skarn mineralization determined from clay/phyllosilicate minerals, Bizmisen-Erzincan, East-Central Turkey
    (Elsevier, 2019) Bozkaya, Omer; Bozkaya, Gulcan; Yilmaz, Huseyin; Hozatlioglu, Deniz; Banks, David A.
    The Bizmilen skarn-type iron deposit is one of the major operating mines in east-central Turkey. Middle Eocene (46.3-42.0 Ma) plutonic rocks (quartz diorite) were intruded into Triassic-Cretaceous limestones and Upper Cretaceous ophiolites forming skarns (garnet, diopside, epidote, scapolite and tremolite), iron mineralization and clay-bearing alteration zones (argillic alteration). Clay-rich rocks of the argillic zone, contain mainly quartz, calcite, dolomite, feldspar and clay/phyllosilicate minerals comprising dioctahedral smectite, kaolinite, mixedlayered illite-smectite (I-S) and illite, and trioctahedral vermiculite, serpentine/chrysotile, talc, chlorite and mixed-layered chlorite-smectite (C-S). Na-Ca smectite, I-S, illite and kaolinite are developed at both the quartz diorite-limestone contact and within the quartz diorite body. However, phlogopite, vermiculite, serpentine/chrysotile, talc and chlorite occur at the quartz diorite-ophiolite contacts, indicating the distributions of clay/phyllosilicate minerals are influenced primarily by the host-rock composition. Chlorite geothermometry data suggest similar to 300 degrees C for the retrograde stage of skarn formation and similar to 120 degrees C for the late argillic alteration overprint, and the formation of low-temperature clays (smectite, vermiculite, C-S) in areas of skarn formation. Kaolinite 1 M (one-layer monoclinic) and I-S (I-75-S-25, R1 ordering) are indicative of low-temperature ( < 200 degrees C) argillic alteration conditions. Optical and electron microscopy studies of kaolinite, smectite and I-S indicate a completely hydrothermal (neo-formation) origin, with the absence of any detrital input. The major and trace/REE wholerock analyses of clays show they have a composition between the analyses of quartz diorite and ophiolite rocks (i.e., serpentinite and serpentinized peridotite). However, the analyses are closest to those of the quartz diorite. The calculated delta O-18 and delta D values of fluids in equilibrium with the clays (using the average values of the fluid inclusion homogenization temperatures) indicate a pre-dominantly magmatic water source. Assuming the clayforming fluids originated from magmatic water, the delta 18O(V-SMOW) and delta DV-SMOW compositions indicate < 200 degrees C for smectite during the supergene or low-temperature argillic stage, but in excess of 200 degrees C for I-S and kaolinite during the hypogene or high-temperature argillic stage. 40Ar/39Ar age data of illite and I-S (37.5-25.5 Ma) indicate alteration started during the late Eocene, similar to 4 Ma after intrusion of the pluton at 42 Ma, and continued to the late Oligocene, with a duration of similar to 12 Ma. The age data imply a long period of cooling at depth, without exhumation, during epithermal alteration after the retrograde skarn stage. The data show that hydrothermal clays formed from magmatic fluids in a hydrothermal system that persisted well after the intrusion of the igneous body and are indicative of how long hydrothermal systems can persist in areas of mineralization.