scholarly journals A geophysical approach to the igneous rocks in the Biga Peninsula (NW Turkey) based on airborne magnetic anomalies: geological implications

2012 ◽  
Vol 25 (3-4) ◽  
pp. 267-285 ◽  
Author(s):  
Yunus Levent Ekinci ◽  
Erdinç Yiğitbaş
Keyword(s):  
Magnetic Anomalies ◽  
Igneous Rocks ◽  
Biga Peninsula ◽  
Nw Turkey ◽  
Geological Implications ◽  
Airborne Magnetic

Acid-sulphate hydrothermal alteration of andesitic tuffs and genesis of halloysite and alunite deposits in the Biga Peninsula, Turkey

Clay Minerals ◽  
2008 ◽  
Vol 43 (2) ◽  
pp. 281-315 ◽  
Author(s):  
Ö. I. Ece ◽  
P. A. Schroeder ◽  
M. J. Smilley ◽  
J. M. Wampler
Keyword(s):  
Hydrothermal Alteration ◽  
Volcanic Rocks ◽  
Geothermal Field ◽  
Parent Material ◽  
Thermal Waters ◽  
Geothermal Waters ◽  
Biga Peninsula ◽  
The North ◽  
Clay Deposits ◽  
Nw Turkey

AbstractThe Biga Peninsula of NW Turkey is host to six major halloysite deposits in the Go¨nen, Yenice and Balya districts. Mineralization took place in areas of Permian limestone blocks where the Triassic Karakaya Complex is in contact with early Miocene calc-alkaline volcanic rocks. Hypogene halloysite mineralization was controlled by the intersection of minor faults in the vicinity of clay deposits. During the Pleistocene, activity of the North Anatolian Fault (NAF) brought ascending geothermal solutions through the fault zones to the surface, which led to hydrothermal alteration and halloysite formation. N-MORB normalized element values for each halloysite deposit and the volcanic rocks suggest genetic links. Alunite and halloysite were formed in the Turplu area where upwelling hydrothermal waters contained major H2S and SO2acids. Only halloysite mineralization occurred in outflow areas of the same fossil geothermal field.Pyrite and alunite samples from the Turplu deposits have δ34S values of 0.6–1.8% and 4.8–7.9%, respectively, with values for gypsum of 3.1–3.5%. The δ34S values of pyrite suggest that local meteoric waters had partially mixed with the dominant fluid during the closure stage of fossil hydrothermal activities. The range of δD values of halloysite samples from Turplu is –58.4 to –68.6%. The δ18O values for halloysite are in the range 16.7–18.1%. All halloysite deposits in the study areas are either overlying or adjacent to limestone blocks, and these provide excellent drainage for the discharging geothermal waters. Subsurface drainage systems in the karstic environment and the SO2-bearing thermal waters indicate the importance of acidic waters and the continuous leaching of elements in forming relatively pure hydrated halloysite. A steam-heated dissolution-precipitation model is proposed for the occurrence of all halloysite and alunite deposits. Sulphur gases (H2S-SO2) of hypogene origin rose from deep in the fault zone to the surface where they encountered oxygenated groundwater at the water table. The occurrence of H2SO4in this hydrothermal system enhanced the acidity of geothermal waters provoking advanced argillic alteration. Hypogene alunite deposits also have large P2O5contents, suggesting a parent material with a magmatic origin deeper than the alkaline tuffs. Halloysite is a fast-forming metastable precursor to kaolinite.

THE UPWARD CONTINUATION OF AN AEROMAGNETIC ANOMALY IN WASHINGTON

Geophysics ◽  
1964 ◽  
Vol 29 (1) ◽  
pp. 109-117
Author(s):  
Nelson C. Steenland ◽  
W. D. Gibbons
Keyword(s):  
Magnetic Anomalies ◽  
Igneous Rocks ◽  
Aeromagnetic Anomaly ◽  
Upward Continuation ◽  
Geologic Map

It is quite common to find large magnetic anomalies originating from igneous rocks, both extrusive and intrusive, especially when they occur at shallow depths. When such rocks crop out, it is straightforward to correlate a particular anomaly with the outcrop. Such is the case with a large observed anomaly in T 14–15N, R 5–6W, Pacific County, Washington, where a large observed anomaly on the USGS (1958) aeromagnetic map may have its source closely identified with an igneous outcrop designated as [Formula: see text], Eocene volcanics, on the geologic map of Washington.

Rutile geochemistry and thermometry of eclogites and associated garnet-mica schists in the Biga Peninsula, NW Turkey

Geochemistry ◽  
2017 ◽  
Vol 77 (3) ◽  
pp. 503-515 ◽  
Author(s):  
Firat Şengün ◽  
Thomas Zack ◽  
Gültekin Topuz
Keyword(s):  
Biga Peninsula ◽  
Nw Turkey
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