Türkiye Jeoloji Bülteni

Abstract: The Oltu-Balkaya basin has started to open by the collision (soft-collision) between Pontide Arc andAnatolide-Tauride Platform since late Maastrihtian and was evolved as collisional foreland basins duringUpper Maastrihtian and Eocene time. At this period, turbiditic continental deposits intercalated withcarbonates, marine deltaic deposits and marine detritics are deposited, from bottom to top, respectively.Middle-Late Eocene shallow marin clastic deposits and high-K volcanics which may be attributed topost collisional magmatism lie on this basin fill characterizing the collisional phase. At the begining ofOligocene time, a molas consisting of continental clastics and shallow marine units with interlayeres ofgypsum and high-K volcanics were deposited on a regional unconformity at the Oligocene-Late Mioceneinterval in the region which was a completely emergent land (hard-final collision) at the end of Eocene.After deposition of the sequence characterizing this period, the region has completely become a land in theMiocene time by compression. Normal faults with NW-SE striking and in the direction of NE - SWdipping are observed in Late Miocene-Early Pliocene units consisting of fluvial to lacustrine completelycontinental deposits and volcanics. A widespread andesitic and dasitic volcanism occured at this periodreflecting an extensional tectonic regime. Late Pliocene-Quaternary semi-consolidated continental clasticdeposits cover these units by ungular unconformity.The Oltu-Balkaya basin is characterized by dominant folding with approximately NE-SW trending axisand a thrust fault striking NE-SW, which dips about 40o northward. These structures as a whole representNW-SW-directed compressional tectonic regime prevailed in the basin at least during Late OligoceneMiocene time. As for the Late Pliocene-Quaternary beds rest on an angular unconformity over the olderunits and this sequence which have not been folded represents Neotectonic period.As a result, the Oltu-Balkaya basin represents a superimposed basin which is syn-collisional in UpperMaastrictian-Middle Eocene, post-collisional in Middle Eocene-Early Pliocene and where the strike-sliperegime dominant since the Late Pliocene to present time (Neotectonic Period).

Abstract: Study area covers Ilıpınar Village and its surrounding area between Aliağa, Menemen and Foça districts,NW of İzmir city. This region is located on İzmir-Ankara Zone (Brinkmann,1966) which is an importanttectonic structure of Paleotectonic era between Sakarya Continent in the North and Menderes Massif in theSouth East. Stratigraphic and structural relations between volcanic/volcanoclastic rocks and terrestrialsediments (mainly river and lake deposits) were studied within approximately 72 km² area. 1/25.000scaled geological map of the area prepared by previous researchers was revised by using GeographicInformation Technologies (GIS) and petrographic/petrologic investigations of hand specimens were alsoanalysed.Within this study, previous geological maps underwent changes, stratigraphical column was revised andlocal stratigraphy was re-evaluated. Accordingly, it was determined that; there happened a terrestrial/lacustrine sedimentation with extensive volcanic activity in Early/Mid Miocene. In Mid-Miocene, lacustrinesedimentation was completed with the sedimentation of limestones of Lacustrine origin. Besides, it wasdetermined that all these units were cut by basalts which is a product of Mid-Miocene volcanism.Benefits of Remote Sensing and Geographic Information Systems (GIS), which is very popular tool inearth sciences, were extensively used. When determining boundaries of different stratigraphic units ingeological mapping, tectonic discontinuities and their interpretation, in addition to GIS applications,different resolution satellite images and Google Earth were widely used

Abstract: Alteration minerals determined in the ultramafic rocks of Güneş Ophiolite were divided in  three maingroups as pre-, syn- and post-serpentinization. Of these, phlogopite from pre-serpentinization mineralsis one of the main components of mica-peridotites and is contemporaneous with the formation of theophiolitic sequence. Listwaenitization and pyrometasomatism from later alterations caused an increase ingrain size and accumulation of phlogopites in certain zones and also mixed-layer phlogopite-vermiculite(P-V) and vermiculite transformations in local. Syn-serpentinization alterations cover the conversionsfrom felsic and mafic minerals to various clay and/or phyllosilicates. Post-serpentinization alterationcovers the occurrences of ophicarbonate (commonly calcite and dolomite, rarely siderite and hydrotalcite),ophioxide-hydroxide (hematite, goethite, pyrite, marcasite and brucite) and locally ophisilicate (quartz) thatrefers to listwaenitization. Phlogopite, actinolite, epidote, johannsenite, scapolite, schorl and Fe-minerals(magnetite, hematite, pyrite, marcasite) form of the products of metasomatism in the pyrometasomaticrocks, and pyroxene and feldspar are residual primary magmatic phases. Divriği phlogopites differ partlyin respect to end-member of theoretical oxide compositions of phlogopite-biotite series. Biotite componentof phlogopites is low (8-14 %) and they are called as Fe-Al phlogopite according to their average unit-cellcomposition. The main cation of P-V in the ultramafic-hosted rocks is Mg and this mineral is partiallyrich in Fe and poor in Al. Serpentines have tetrahedral and octahedral Fe substitutions which indicateFe-lizardite. The concentrations of total trace element in the phyllosilicate minerals decrease fromserpentine–phlogopite to P-V, whereas their rare earth element contents increase in the same directionin the Divriği area. δ18O and δD values (SMOW) are determined as ‰ +10.6-11.8 and ‰ −64 - −102 forphlogopites, ‰ +14.2 and ‰ −121 for P-V, and ‰ +14.4 and ‰ −129 for serpentine. Phlogopites areplot hypogene and supergene fields, but P-V and serpentine are found under kaolinite weathering line onthe basis of δ18O and δD values. Formation temperatures as ~ 130-150 °C for phlogopite and ~ 100 °Cfor P-V are obtained on the comparison of minimum isotopic value of granitic water. Additionally, stableisotopic values showed that serpentinization, phlogopitization and vermiculitization formed with differentsubsequent processes.

Abstract: This study presents geological and geochemical features of gold deposit located in Sisorta area nearEvliya Tepe, Güzelyurt village. The investigation area covers 42 km2 land and located in 200 km NW ofSivas province in Sisorta. .δ 34S ‰ isotope values are ranging from -0,4 and ‰ ‰ 22, in Sisorta gold deposit. At the early stage ofmineralization S isotope value number is light and later S isotope value shows heavy numbers. This isindicating that the S isotope was originated from magma and changed due to temperature variations inthe last stages of the hydrothermal process.δ18O isotope values of gangue minerals are ranging from; ‰ 7,1 and ‰ 15,6 however, δD value is rangingfrom ‰ -77 to ‰ -25,3 Combining δ18O with δD from Sisorta samples, demonstrates meteoric waters wereimportant in the formation of the alteration silicate minerals analyzed. This is common in high sulfidationsilicate alteration minerals.40Ar/ 39Ar age dating is ranging from 78,85±0,94 Ma and 76,59±2,19 Ma as a plateau age and 78,25±0,42Ma and 75,30±0,90 Ma as isochron age in K-alunite, 80,44±0,84 in hornblende minerals from unalteredandesitic volcanic rocks. This shows that hydrothermal gold mineralization is deposited 3 Ma later thanthe volcanic host rock eruption.δ 65Cu ‰ values from copper-bearing minerals associated with Sisorta gold deposits are ranging from-5.502 ‰ to +3.032 ‰. The copper isotope values closest to the intrusions (deepest part of the system) donot show significant copper isotope variations (<1 per mil), in contrast the upper parts of the system showlarge copper isotope variations and indicate enrichment of copper due to supergene processes.