Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Tu... more Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Turkey were investigated through high-resolution U-series geochronology, microstructural and geochemical studies including C–O–Sr isotope and rare-earth element and yttrium (REY) analyses. Petrographical observations and geochronological data are interpreted as evidence that the calcite veins formed through a crack-seal mechanism, mostly accompanied/initiated by intensive hydraulic fracturing of the host limestone in response to high-pressure fluids, which is manifested by multi-stage breccia deposits. Microscale U-series dates (272.6–20.5 kyr) and geochemical compositions of the vein/breccia samples provide information on the timing and mechanism of the vein formation and identify the source of CO 2-bearing fluids responsible for the carbonate precipitation. d 18 O VPDB and d 13 C VPDB values of the calcite veins range between À5.9 and À1.7‰, and À10.6 and À4.6‰, respectively. The isotopic compositions of the veins show highly fluctuating values as calcite grew successively perpendicular to vein walls, which, in combination with microstructural and geochronological constraints, are interpreted to reflect episodic CO 2 degas-sing events associated with seismic and aseismic deformation. Oxygen and Sr isotope compositions (d 18 O VPDB : À5.9 to À1.7‰; 87 Sr/ 86 Sr: 0.7082 to 0.7085) together with REY concentrations indicate deep infiltration of meteoric waters with various degrees of interactions mostly with the host limestone and siliciclastic parts of the basement rocks. Oxygen and carbon isotope compositions suggest CO 2 degassing through intensive limestone dissolution. While majority of the veins display similar Post-Archaean Australian Shale (PAAS)-normalised REY variations, some of the veins show positive Eu PAAS anomalies, which could be indicative of contributions from a deeply derived, heated, and reduced fluid component, giving rise to multiple fluid sources for the calcite veins. Vein calcite formed in fault-induced fractures offers insights into structural features, genetic characterisation of the parental fluids, and late Quaternary degassing of subsurface CO 2 accumulations.
Multiple climate-sensitive trace element/Ca and stable isotope (O and C) profiles derived from Di... more Multiple climate-sensitive trace element/Ca and stable isotope (O and C) profiles derived from Dim Cave speleothems (S-SW Turkey) provide evidence of climatic changes and define a series of palaeohydrological conditions for the period ~10–90 kyr. Dim Cave speleothem Mg/Ca, Sr/Ca, U/Ca, Ba/Ca, and Y/Ca ratios demonstrate similar patterns over glacial–interglacial scales, in agreement with δ 18 O and δ 13 C records. Three episodes of more positive moisture balance (71–63 kyr, 51–40 kyr, and 18–10 kyr) were observed based on Y/Ca (and to a lesser extent Zr/Ca), 87 Sr/ 86 Sr ratios, calcite micromorphology, and growth rates. Increasing concentrations of Y, Zr (and U) and elevated 87 Sr/ 86 Sr ratios are attributed to enhanced levels of terrestrial input during these periods. Correlations between δ 13 C, δ 18 O and Mg/Ca during 40–18 kyr (corresponding with the lowest growth rate of ~0.8 mm/ kyr), 63–51, and 80–71 kyr (relatively low growth rates), as well as co-varying and enhanced Mg/Ca, Sr/Ca, and to a lesser extent Ba/Ca, ratios point to the prior calcite precipitation, wall rock interaction, and preferential dolo-mite dissolution over calcite in the host dolomitic limestone during these periods. This relationship suggests that water–rock interactions are maximised during episodes of slower drip rates of water through the karst under drier conditions. Chondrite-normalised rare earth element and yttrium (REY) patterns of the stalagmites reveal seawater signatures closely linked to the dolomitic limestone. Excluding the aragonite formation during ~80–75 kyr, which is an autogenic effect, trace element/Ca ratios appear to respond to millennial scale global cooling periods such as Heinrich events.
ABSTRACT Electron spin resonance (ESR) and 230Th/234U ages of speleothem samples collected from k... more ABSTRACT Electron spin resonance (ESR) and 230Th/234U ages of speleothem samples collected from karstic caves located around 3000 m elevation in the Aladağlar Mountain Range (AMR), south-central Turkey, were determined in order to provide new insight and information regarding late Pleistocene climate. ESR ages were validated with the 230Th/234U ages of test samples. The ESR ages of 21 different layers of six speleothem samples were found to range mostly between about 59 and 4 ka, which cover the Marine Oxygen Isotope Stages (MIS) MIS 3 to MIS 1. Among all, only six layers appear to have deposited during MIS 8 and 5. Most of the samples dated were deposited during the late glacial stage (MIS 2). It appears that a cooler climate with a perennial and steady recharge was more conducive to speleothem development rather than a warmer climate with seasonal recharge in the AMR during the late Quaternary. This argument supports previous findings that suggest a two -fold increase in last glacial maximum mean precipitation in Turkey with respect to the present value.
Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Tur... more Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Turkey) and Dead Sea (Israel) fault zones were investigated structurally, geochemically and geochronologically. The results indicate major differences in the nature of calcite precipitates and temporal relationship to faulting. In the Düziçi Fault, calcite-filled veins and hydraulic fractures precipitated co-seismically during three consecutive faulting events. Calcite precipitated in veins at the Har Zefiyya Fault was controlled by near-surface karst processes. Initial opening of the veins occurred prior to about 500 ka and may represent the onset of an east-west contractional deformation. In the Carmel Fault Zone the calcite coating the fault plane precipitated by karst processes, with no evidence of subsequent deformation. Calcite fault gouge from the same site are a mix of host-rock gouge and newly formed authigenic calcite, and their overall geochemistry suggests pervasive fluid-rock interaction in the fault zone. In the Baraq Fault Zone the precipitation of calcite within syntectonic tension gashes and veins occurred prior to 540 ka by the pervasive infiltration of meteoric water into the fault zone. The results demonstrate that geochemical and structural analyses, combined with U-Th geochronology, can shed light on co-seismic and interseismic fault activity, and can potentially provide precise age constraints on the timing of brittle deformation.
We present a method to constrain the timing of fissure generation related to late Quaternary seis... more We present a method to constrain the timing of fissure generation related to late Quaternary seismic events using the uranium-series technique. Dated samples were from travertine deposits precipitated in co-seismic extensional fissures along major active faults in Western Turkey. Stable isotope and REE data indicate that the precipitation of the fissure travertines was not controlled by the hydrologic regime that is responsible for the speolethem deposition in the same region. Moreover, the REE composition and concentration of the water from which the fissure travertine precipitated were significantly different from those of the current geothermal waters in the study area. The carbonate generation in the co-seismic fissures is interpreted to be the product of rapid precipitation from deeply infiltrated and CO 2 -enriched surface water during seismic strain cycles. Results show that U-series dating of fracture-filling travertine deposits from seismically active areas provide important temporal information relevant to establishing recurrence intervals of late Quaternary and prehistoric major earthquake events. Precise dating of prehistoric earthquakes may be of great value for seismic hazard studies and earthquake forecasting research, for which accurate estimates of recurrence intervals are critical.
Geological Society, London, Special Publications, 2011
Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Tur... more Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Turkey) and Dead Sea (Israel) fault zones were investigated structurally, geochemically and geochronologically. The results indicate major differences in the nature of calcite precipitates and temporal relationship to faulting. In the Düziçi Fault, calcite-filled veins and hydraulic fractures precipitated co-seismically during three consecutive faulting events. Calcite precipitated in veins at the Har Zefiyya Fault was controlled by near-surface karst processes. Initial opening of the veins occurred prior to about 500 ka and may represent the onset of an east-west contractional deformation. In the Carmel Fault Zone the calcite coating the fault plane precipitated by karst processes, with no evidence of subsequent deformation. Calcite fault gouge from the same site are a mix of host-rock gouge and newly formed authigenic calcite, and their overall geochemistry suggests pervasive fluid-rock interaction in the fault zone. In the Baraq Fault Zone the precipitation of calcite within syntectonic tension gashes and veins occurred prior to 540 ka by the pervasive infiltration of meteoric water into the fault zone. The results demonstrate that geochemical and structural analyses, combined with U-Th geochronology, can shed light on co-seismic and interseismic fault activity, and can potentially provide precise age constraints on the timing of brittle deformation.
A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two ... more A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two locations at eastern part of the North Anatolian Fault Zone (NAFZ). The fault gouge samples contain no 2 M mica and consist chiefly of cryptocrystalline material, which is extensively altered to illitic clays (mixed-layered illite-smectite) and some carbonate minerals. The Rb-Sr isochrones of leachate, residue and untreated aliquots from various size fractions of samples yielded two different illite generations. The oldest illite authigenesis, which started at about 35.6 Ma might be inherited from pre-existing faults along the Tethyan suture zone. The authigenic illites from finer fractions correspond to an isochron age of 8.3 Ma, which is in agreement with the findings of previous works that may suggest a middle Miocene age for the initiation of the NAFZ. Our Sr isotope data indicate that the metamorphic fluids contain some mantle components and mobilised during fault movement.
A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two ... more A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two locations at eastern part of the North Anatolian Fault Zone (NAFZ). The fault gouge samples contain no 2 M mica and consist chiefly of cryptocrystalline material, which is extensively altered to illitic clays (mixed-layered illite-smectite) and some carbonate minerals. The Rb-Sr isochrones of leachate, residue and untreated aliquots from various size fractions of samples yielded two different illite generations. The oldest illite authigenesis, which started at about 35.6 Ma might be inherited from pre-existing faults along the Tethyan suture zone. The authigenic illites from finer fractions correspond to an isochron age of 8.3 Ma, which is in agreement with the findings of previous works that may suggest a middle Miocene age for the initiation of the NAFZ. Our Sr isotope data indicate that the metamorphic fluids contain some mantle components and mobilised during fault movement.
This study presents the first attempt to constrain the evolution of the North Anatolian Fault Zon... more This study presents the first attempt to constrain the evolution of the North Anatolian Fault Zone (NAFZ) by age dating and isotope tracing of clay minerals formed during near-surface faulting. Extensive illitic clay mineralisation occurred along the NAFZ related to hydrothermal alteration of the fault gouges and pseudotachylytes. Samples representing the pre-fault protoliths outside the fault zone do not contain authigenic illitic clay minerals indicating that hydrothermal processes were confined to the areas within the fault zone. K-Ar age data indicate that the hydrothermal system and the associated illite authigenesis initiated at ∼57 Ma. This process is interpreted to reflect the onset of significant strike-slip or transtensional faulting immediately after the continental collision related to the closure of the Neotethys Ocean. Following the initiation of the fault movements in the latest Paleocene-Early Eocene, displacements along the NAFZ have continued, with probably intensified fault activities at ∼26 Ma and later than ∼8 Ma. Oxygen isotope compositions of the illitic clays from different locations along the NAFZ are similar, with narrow ranges in δ 18 O values indicating clay precipitation from fluids with similar oxygen isotope compositions and crystallisation temperatures. The δ 18 O and δD values of the calculated fluid isotopic composition (δ 18 O = 5.9‰ to 11.2‰, δD = −59‰ to −73‰) are consistent with metamorphic and magmatic origin of fluids mobilised during active tectonism. The interpretation of the fluid flow history of the NAFZ is in agreement with that reported previously for some well-known large-scale high-angle fault zones, which similarly developed along collisional-type orogenic belts and are commonly associated with significant mesothermal ore mineralisation.
We present a new approach to identifying the source and age of paleofluids associated with low-te... more We present a new approach to identifying the source and age of paleofluids associated with low-temperature deformation in the brittle crust, using hydrogen isotopic compositions (dD) and 40 Ar/ 39 Ar geochronology of authigenic illite in clay gouge-bearing fault zones. The procedure involves grain-size separation, polytype modeling, and isotopic analysis, creating a mixing line that is used to extrapolate to dD and age of pure authigenic and detrital material. We use this method on samples collected along the surface trace of today's North Anatolian Fault (NAF). dD values of the authigenic illite population, obtained by extrapolation, are 289 6 3&, 290 6 2&, and 297 6 2& (VSMOW) for samples KSL, RES4-1, and G1G2, respectively. These correspond to dD fluid values of 262& to 285& for the temperature range of 1258C 6 258, indistinguishable from present-day precipitation values. dD values of the detrital illite population are 245 6 13&, 260 6 6&, and 264 6 6& for samples KSL, G1G2, and RES4-1, respectively. Corresponding dD fluid values at 3008C are 226& to 245& and match values from adjacent metamorphic terranes. Corresponding clay gouge ages are 41.4 6 3.4 Ma (authigenic) and 95.8 6 7.7 Ma (detrital) for sample G2 and 24.6 6 1.6 Ma (authigenic) and 96.5 6 3.8 Ma (detrital) for sample RES4-1, demonstrating a long history of meteoric fluid infiltration in the area. We conclude that today's NAF incorporated preexisting, weak clay-rich rocks that represent earlier mineralizing fluid events. The samples preserve at least three fluid flow pulses since the Eocene and indicate that meteoric fluid has been circulating in the upper crust in the North Anatolian Keirogen since that time.
Speleothem-based stable isotope records are valuable in sub-humid and semi-arid settings where ma... more Speleothem-based stable isotope records are valuable in sub-humid and semi-arid settings where many other terrestrial climate proxies are fragmentary. The Eastern Mediterranean is one such region. Here we present an 80-kyr-long precisely-dated (by U-series) and high-resolution oxygen (δ 18 O) and carbon (δ 13 C) records from Dim Cave (~36°N) in SW Turkey. The glacial-interglacial δ 18 O variations in the Dim Cave speleothem are best explained in terms of changes in the trajectories of winter westerly air masses. These are along a northerly (European) track (isotopically less depleted) during the early last glaciation but are gradually depressed southward closer to the modern westerly track along the North African coast (more depleted) after c.50 kyr and remain in the southern track through the Last Glacial Maximum. The southward displacement of the westerly track reflects growth of the Fennoscandian ice sheet and its impact on westerly wind fields. Changes in δ 13 C are interpreted as reflecting soil organic matter composition and/or thickness. δ 13 C values are significantly more negative in interglacials reflecting active carbonic acid production in the soil and less negative in glacial times reflecting carbonate rock values. Several Heinrich events are recorded in the Dim record indicating intensification of westerly flow across this part of the EM.
The geochemical features of the volatiles dissolved in artesian thermal waters discharged over th... more The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins (Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO 2 up to about 340 mlSTP/L H2O marked by a δ 13 C TDC (Total Dissolved Carbon) ranging from −16.9 to +0.18‰ vs PDB, while CH 4 concentrations vary from 4.4 × 10 −5 to 4.9 mlSTP/L H2O . Helium contents were between 9 and N 2800 times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12 mlSTP/L H2O . Helium isotopic composition was in the 0.02-0.21 Ra range (Ra = air-normalized 3 He/ 4 He ratio). The three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the west-central and hottest part of the GAB despite no evidence of recent volcanism. We found that the partial pressure of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian waters from a vast area of N542,000 km 2 , provide new constraints on volatile injection, and show that fluids' geochemistry can provide additional and independent information on the geo-tectonic settings of the Great Artesian Basin and its geothermal potential.
The Eastern Warburton Basin, Northeast South Australia, features major geophysical anomalies, inc... more The Eastern Warburton Basin, Northeast South Australia, features major geophysical anomalies, including a magnetic high of near-200 nT centred on a~25 km-wide magnetic low (b100 nT), interpreted in terms of a magmatic body below 6 km depth. A distinct seismic tomographic low velocity anomaly may reflect its thick (9.5 km) sedimentary section, high temperatures and possible deep fracturing. Scanning electron microscope (SEM) analyses of granites resolves microbreccia veins consisting of micron-scale particles injected into resorbed quartz grains. Planar and sub-planar elements in quartz grains (Qz/PE) occur in granites, volcanics and sediments of the >30,000 km-large Eastern Warburton Basin. The Qz/PE include multiple intersecting planar to curved sub-planar elements with relic lamellae less than 2 μm wide with spacing of 4-5 μm. Qz/PE are commonly re-deformed, displaying bent and wavy patterns accompanied with fluid inclusions. U-stage measurements of a total of 243 planar sets in 157 quartz grains indicate dominance of ∏{10-12}, ω{10-13} and subsidiary §{11-22}, {22-41}, m{10-11} and x{51-61} planes. Transmission Electron Microscopy (TEM) analysis displays relic narrow ≤1 μm-wide lamellae and relic non-sub grain boundaries where crystal segments maintain optical continuity. Extensive sericite alteration of feldspar suggests hydrothermal alteration to a depth of~500 m below the unconformity which overlies the Qz/PE-bearing Warburton Basin terrain. The data are discussed in terms of (A) Tectonic-metamorphic deformation and (B) impact shock metamorphism producing planar deformation features (Qz/PDF). Deformed Qz/PE are compared to re-deformed Qz/PDFs in the Sudbury, Vredefort, Manicouagan and Charlevoix impact structures. A 4-5 km uplift of the Big Lake Granite Suite during 298-295 Ma is consistent with missing of upper Ordovician to Devonian strata and possible impact rebound. The occurrence of circular seismic tomography anomalies below the east Warburton Basin, the Poolowana Basin and the Woodleigh impact structure signifies a potential diagnostic nature of circular tomographic anomalies.
The discovery of large asteroid impact structures, likely and possible impact structures, onshore... more The discovery of large asteroid impact structures, likely and possible impact structures, onshore and offshore the Australian continent Woodleigh [120 km;~360 Ma], Gnargoo [75 km; Lower Permianupper Cretaceous], Tookoonooka [55-65 km;~125 Ma], Talundilly [~84 km;~125 Ma], Mount Ashmore [N 100 km; end-Eocene] and Warburton twin structures [>400km; pre-end Carboniferous]) requires re-examination of the diagnostic criteria used for their identification. Bouguer anomalies of established impact structures (Chicxulub [170 km; 64.98 ± 0.05 Ma], Woodleigh impact structure and Gnargoo probable impact structure display a unique structural architecture where pre-impact structural ridges are intersected and truncated by the outer ring of the circular structure. Seismic reflection data outline circular central uplift domes, basement plugs and rim synclines. Sharp circular seismic tomography anomalies indicate low velocity columns under both the Woodleigh impact structure and Warburton probable impact, hinting at deep crustal fracturing. Deformed, curved and clouded intra-crystalline planar deformation features in quartz (Qz/PDFs), displaying Miller indices ({10-11}, {10-12}, {10-13}) diagnostic of shock metamorphism, abound around exposed established impact structures (Vredefort [298 km; 2023 ± 4 Ma], Sudbury [~250 km; 1850 ± 3 Ma], Charlevoix [54 km; 342 ± 15 Ma], Manicouagan [100 km; 214 ± 1 Ma])
The Savcili Fault Zone represents one of the most prominent regional-scale intraplate fault syste... more The Savcili Fault Zone represents one of the most prominent regional-scale intraplate fault systems in central Turkey, recording the collisional events following the closure of Neo-Tethys in the eastern Mediterranean region. It consists of anastomosing reverse/thrust faults with WNW-ESE direction that placed rocks of the Central Anatolian Crystalline Complex on Paleogene sedimentary units. Structural measurements and kinematic indicators show that faults within the Savcili Fault Zone (SFZ) have top to the NE and NW sense of brittle deformation. Stable isotope (δ 18 O and δ D) and trace element data indicate that fault gouge illites precipitated from deep basinal brines. These fluids were mobilized during phases of compressional deformation and migrated upward along thrust faults toward shallow brittle deformation zones. Rb-Sr and Ar-Ar geochronology of fault gouges in two cataclastic zones demonstrates age variability for two different dating techniques (Rb-Sr: 40.9 ± 1.5 Ma and 22.9 ± 1.3 Ma; Ar-Ar: 46.45 ± 0.25 Ma and 29.8 ± 0.13 Ma). We argue that Rb-Sr dating provides ages more closely reflecting the timing of fault movements because of potential contamination of illite by excess 40 Ar. Accordingly, the SFZ was active during at least two phases; the middle Eocene and late Oligocene to early Miocene, which is consistent with the relative age constraints suggested by field relationships. Geochronology combined with structural field evidence indicates a rapid change in stress regime from extension to contraction at~40 Ma that continued until at least~23 Ma. Direct dating of brittle faulting provides a prolific approach for determining the absolute timing of tectonic events in areas that have largely relied on indirect information.
The metaluminous Soultz-sous-Forêts monzogranite, France, is highly evolved and contains elevated... more The metaluminous Soultz-sous-Forêts monzogranite, France, is highly evolved and contains elevated concentrations of rare-earth elements (REE), Y and particularly Th. Primary accessory minerals include fluorapatite, allanite-(Ce) and Th-rich titanite. Primary titanite has been altered to anatase + calcite + quartz + synchysite-(Ce) ± bastnaesite-(Ce) or anatase + calcite + quartz + monazite-(Ce) + xenotime-(Y) ± thorite. Fluorocarbonate-bearing assemblages are restricted to those samples exhibiting minor selective alteration, whereas those containing phosphate-rich assemblages formed in pervasively altered samples that have experienced high fluid/rock ratios. Comparative electron-microprobe analysis of primary and hydrothermallyderived accessory phases found middle REE, Y and Th concentrations depleted in synchysite-(Ce) relative to primary titanite. Such depletions are not seen in phosphate-rich samples containing monazite-(Ce) and xenotime-(Y). Variability in elemental concentrations may be attributed to distinct fluid chemistries and hence, lead to differential mobility during alteration. Following previous experimental work and mineralogical observations, the ingress of CO 2 -rich solutions was integral for titanite breakdown and the resultant metasomatic assemblage. The influx of CO 2 -rich fluids concomitantly with chloritisation of biotite produced fluids enriched in FCO 3 − . We, therefore, hypothesise that after the alteration of titanite, remnant HCO 3 − or FCO 3 − -rich fluids were able to mobilise significant proportions of MREE, Y and Th not accommodated into the synchysite-(Ce) structure. Conversely, those samples rich in monazite-(Ce) and xenotime-(Y) retained their REE, Y and Th concentrations due to the presence of aqueous HPO 4 2− derived from apatite dissolution.
Geochronological (U-Pb, U-Th-total Pb, Sm-Nd) and geochemical (REE, 87 Sr/ 86 Sr, δ 18 O, δ 13 C)... more Geochronological (U-Pb, U-Th-total Pb, Sm-Nd) and geochemical (REE, 87 Sr/ 86 Sr, δ 18 O, δ 13 C) tracing of intraplate tectonism and associated fluid flow in the Warburton Basin, Australia
Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Tu... more Vein and breccia carbonates precipitated in a highly fractured/faulted carbonate bedrock in SW Turkey were investigated through high-resolution U-series geochronology, microstructural and geochemical studies including C–O–Sr isotope and rare-earth element and yttrium (REY) analyses. Petrographical observations and geochronological data are interpreted as evidence that the calcite veins formed through a crack-seal mechanism, mostly accompanied/initiated by intensive hydraulic fracturing of the host limestone in response to high-pressure fluids, which is manifested by multi-stage breccia deposits. Microscale U-series dates (272.6–20.5 kyr) and geochemical compositions of the vein/breccia samples provide information on the timing and mechanism of the vein formation and identify the source of CO 2-bearing fluids responsible for the carbonate precipitation. d 18 O VPDB and d 13 C VPDB values of the calcite veins range between À5.9 and À1.7‰, and À10.6 and À4.6‰, respectively. The isotopic compositions of the veins show highly fluctuating values as calcite grew successively perpendicular to vein walls, which, in combination with microstructural and geochronological constraints, are interpreted to reflect episodic CO 2 degas-sing events associated with seismic and aseismic deformation. Oxygen and Sr isotope compositions (d 18 O VPDB : À5.9 to À1.7‰; 87 Sr/ 86 Sr: 0.7082 to 0.7085) together with REY concentrations indicate deep infiltration of meteoric waters with various degrees of interactions mostly with the host limestone and siliciclastic parts of the basement rocks. Oxygen and carbon isotope compositions suggest CO 2 degassing through intensive limestone dissolution. While majority of the veins display similar Post-Archaean Australian Shale (PAAS)-normalised REY variations, some of the veins show positive Eu PAAS anomalies, which could be indicative of contributions from a deeply derived, heated, and reduced fluid component, giving rise to multiple fluid sources for the calcite veins. Vein calcite formed in fault-induced fractures offers insights into structural features, genetic characterisation of the parental fluids, and late Quaternary degassing of subsurface CO 2 accumulations.
Multiple climate-sensitive trace element/Ca and stable isotope (O and C) profiles derived from Di... more Multiple climate-sensitive trace element/Ca and stable isotope (O and C) profiles derived from Dim Cave speleothems (S-SW Turkey) provide evidence of climatic changes and define a series of palaeohydrological conditions for the period ~10–90 kyr. Dim Cave speleothem Mg/Ca, Sr/Ca, U/Ca, Ba/Ca, and Y/Ca ratios demonstrate similar patterns over glacial–interglacial scales, in agreement with δ 18 O and δ 13 C records. Three episodes of more positive moisture balance (71–63 kyr, 51–40 kyr, and 18–10 kyr) were observed based on Y/Ca (and to a lesser extent Zr/Ca), 87 Sr/ 86 Sr ratios, calcite micromorphology, and growth rates. Increasing concentrations of Y, Zr (and U) and elevated 87 Sr/ 86 Sr ratios are attributed to enhanced levels of terrestrial input during these periods. Correlations between δ 13 C, δ 18 O and Mg/Ca during 40–18 kyr (corresponding with the lowest growth rate of ~0.8 mm/ kyr), 63–51, and 80–71 kyr (relatively low growth rates), as well as co-varying and enhanced Mg/Ca, Sr/Ca, and to a lesser extent Ba/Ca, ratios point to the prior calcite precipitation, wall rock interaction, and preferential dolo-mite dissolution over calcite in the host dolomitic limestone during these periods. This relationship suggests that water–rock interactions are maximised during episodes of slower drip rates of water through the karst under drier conditions. Chondrite-normalised rare earth element and yttrium (REY) patterns of the stalagmites reveal seawater signatures closely linked to the dolomitic limestone. Excluding the aragonite formation during ~80–75 kyr, which is an autogenic effect, trace element/Ca ratios appear to respond to millennial scale global cooling periods such as Heinrich events.
ABSTRACT Electron spin resonance (ESR) and 230Th/234U ages of speleothem samples collected from k... more ABSTRACT Electron spin resonance (ESR) and 230Th/234U ages of speleothem samples collected from karstic caves located around 3000 m elevation in the Aladağlar Mountain Range (AMR), south-central Turkey, were determined in order to provide new insight and information regarding late Pleistocene climate. ESR ages were validated with the 230Th/234U ages of test samples. The ESR ages of 21 different layers of six speleothem samples were found to range mostly between about 59 and 4 ka, which cover the Marine Oxygen Isotope Stages (MIS) MIS 3 to MIS 1. Among all, only six layers appear to have deposited during MIS 8 and 5. Most of the samples dated were deposited during the late glacial stage (MIS 2). It appears that a cooler climate with a perennial and steady recharge was more conducive to speleothem development rather than a warmer climate with seasonal recharge in the AMR during the late Quaternary. This argument supports previous findings that suggest a two -fold increase in last glacial maximum mean precipitation in Turkey with respect to the present value.
Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Tur... more Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Turkey) and Dead Sea (Israel) fault zones were investigated structurally, geochemically and geochronologically. The results indicate major differences in the nature of calcite precipitates and temporal relationship to faulting. In the Düziçi Fault, calcite-filled veins and hydraulic fractures precipitated co-seismically during three consecutive faulting events. Calcite precipitated in veins at the Har Zefiyya Fault was controlled by near-surface karst processes. Initial opening of the veins occurred prior to about 500 ka and may represent the onset of an east-west contractional deformation. In the Carmel Fault Zone the calcite coating the fault plane precipitated by karst processes, with no evidence of subsequent deformation. Calcite fault gouge from the same site are a mix of host-rock gouge and newly formed authigenic calcite, and their overall geochemistry suggests pervasive fluid-rock interaction in the fault zone. In the Baraq Fault Zone the precipitation of calcite within syntectonic tension gashes and veins occurred prior to 540 ka by the pervasive infiltration of meteoric water into the fault zone. The results demonstrate that geochemical and structural analyses, combined with U-Th geochronology, can shed light on co-seismic and interseismic fault activity, and can potentially provide precise age constraints on the timing of brittle deformation.
We present a method to constrain the timing of fissure generation related to late Quaternary seis... more We present a method to constrain the timing of fissure generation related to late Quaternary seismic events using the uranium-series technique. Dated samples were from travertine deposits precipitated in co-seismic extensional fissures along major active faults in Western Turkey. Stable isotope and REE data indicate that the precipitation of the fissure travertines was not controlled by the hydrologic regime that is responsible for the speolethem deposition in the same region. Moreover, the REE composition and concentration of the water from which the fissure travertine precipitated were significantly different from those of the current geothermal waters in the study area. The carbonate generation in the co-seismic fissures is interpreted to be the product of rapid precipitation from deeply infiltrated and CO 2 -enriched surface water during seismic strain cycles. Results show that U-series dating of fracture-filling travertine deposits from seismically active areas provide important temporal information relevant to establishing recurrence intervals of late Quaternary and prehistoric major earthquake events. Precise dating of prehistoric earthquakes may be of great value for seismic hazard studies and earthquake forecasting research, for which accurate estimates of recurrence intervals are critical.
Geological Society, London, Special Publications, 2011
Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Tur... more Fault-related calcite precipitates taken from different segments along the East Anatolian (SE Turkey) and Dead Sea (Israel) fault zones were investigated structurally, geochemically and geochronologically. The results indicate major differences in the nature of calcite precipitates and temporal relationship to faulting. In the Düziçi Fault, calcite-filled veins and hydraulic fractures precipitated co-seismically during three consecutive faulting events. Calcite precipitated in veins at the Har Zefiyya Fault was controlled by near-surface karst processes. Initial opening of the veins occurred prior to about 500 ka and may represent the onset of an east-west contractional deformation. In the Carmel Fault Zone the calcite coating the fault plane precipitated by karst processes, with no evidence of subsequent deformation. Calcite fault gouge from the same site are a mix of host-rock gouge and newly formed authigenic calcite, and their overall geochemistry suggests pervasive fluid-rock interaction in the fault zone. In the Baraq Fault Zone the precipitation of calcite within syntectonic tension gashes and veins occurred prior to 540 ka by the pervasive infiltration of meteoric water into the fault zone. The results demonstrate that geochemical and structural analyses, combined with U-Th geochronology, can shed light on co-seismic and interseismic fault activity, and can potentially provide precise age constraints on the timing of brittle deformation.
A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two ... more A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two locations at eastern part of the North Anatolian Fault Zone (NAFZ). The fault gouge samples contain no 2 M mica and consist chiefly of cryptocrystalline material, which is extensively altered to illitic clays (mixed-layered illite-smectite) and some carbonate minerals. The Rb-Sr isochrones of leachate, residue and untreated aliquots from various size fractions of samples yielded two different illite generations. The oldest illite authigenesis, which started at about 35.6 Ma might be inherited from pre-existing faults along the Tethyan suture zone. The authigenic illites from finer fractions correspond to an isochron age of 8.3 Ma, which is in agreement with the findings of previous works that may suggest a middle Miocene age for the initiation of the NAFZ. Our Sr isotope data indicate that the metamorphic fluids contain some mantle components and mobilised during fault movement.
A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two ... more A combined mineralogical and Rb-Sr isotopic investigation was conducted on fault gouges from two locations at eastern part of the North Anatolian Fault Zone (NAFZ). The fault gouge samples contain no 2 M mica and consist chiefly of cryptocrystalline material, which is extensively altered to illitic clays (mixed-layered illite-smectite) and some carbonate minerals. The Rb-Sr isochrones of leachate, residue and untreated aliquots from various size fractions of samples yielded two different illite generations. The oldest illite authigenesis, which started at about 35.6 Ma might be inherited from pre-existing faults along the Tethyan suture zone. The authigenic illites from finer fractions correspond to an isochron age of 8.3 Ma, which is in agreement with the findings of previous works that may suggest a middle Miocene age for the initiation of the NAFZ. Our Sr isotope data indicate that the metamorphic fluids contain some mantle components and mobilised during fault movement.
This study presents the first attempt to constrain the evolution of the North Anatolian Fault Zon... more This study presents the first attempt to constrain the evolution of the North Anatolian Fault Zone (NAFZ) by age dating and isotope tracing of clay minerals formed during near-surface faulting. Extensive illitic clay mineralisation occurred along the NAFZ related to hydrothermal alteration of the fault gouges and pseudotachylytes. Samples representing the pre-fault protoliths outside the fault zone do not contain authigenic illitic clay minerals indicating that hydrothermal processes were confined to the areas within the fault zone. K-Ar age data indicate that the hydrothermal system and the associated illite authigenesis initiated at ∼57 Ma. This process is interpreted to reflect the onset of significant strike-slip or transtensional faulting immediately after the continental collision related to the closure of the Neotethys Ocean. Following the initiation of the fault movements in the latest Paleocene-Early Eocene, displacements along the NAFZ have continued, with probably intensified fault activities at ∼26 Ma and later than ∼8 Ma. Oxygen isotope compositions of the illitic clays from different locations along the NAFZ are similar, with narrow ranges in δ 18 O values indicating clay precipitation from fluids with similar oxygen isotope compositions and crystallisation temperatures. The δ 18 O and δD values of the calculated fluid isotopic composition (δ 18 O = 5.9‰ to 11.2‰, δD = −59‰ to −73‰) are consistent with metamorphic and magmatic origin of fluids mobilised during active tectonism. The interpretation of the fluid flow history of the NAFZ is in agreement with that reported previously for some well-known large-scale high-angle fault zones, which similarly developed along collisional-type orogenic belts and are commonly associated with significant mesothermal ore mineralisation.
We present a new approach to identifying the source and age of paleofluids associated with low-te... more We present a new approach to identifying the source and age of paleofluids associated with low-temperature deformation in the brittle crust, using hydrogen isotopic compositions (dD) and 40 Ar/ 39 Ar geochronology of authigenic illite in clay gouge-bearing fault zones. The procedure involves grain-size separation, polytype modeling, and isotopic analysis, creating a mixing line that is used to extrapolate to dD and age of pure authigenic and detrital material. We use this method on samples collected along the surface trace of today's North Anatolian Fault (NAF). dD values of the authigenic illite population, obtained by extrapolation, are 289 6 3&, 290 6 2&, and 297 6 2& (VSMOW) for samples KSL, RES4-1, and G1G2, respectively. These correspond to dD fluid values of 262& to 285& for the temperature range of 1258C 6 258, indistinguishable from present-day precipitation values. dD values of the detrital illite population are 245 6 13&, 260 6 6&, and 264 6 6& for samples KSL, G1G2, and RES4-1, respectively. Corresponding dD fluid values at 3008C are 226& to 245& and match values from adjacent metamorphic terranes. Corresponding clay gouge ages are 41.4 6 3.4 Ma (authigenic) and 95.8 6 7.7 Ma (detrital) for sample G2 and 24.6 6 1.6 Ma (authigenic) and 96.5 6 3.8 Ma (detrital) for sample RES4-1, demonstrating a long history of meteoric fluid infiltration in the area. We conclude that today's NAF incorporated preexisting, weak clay-rich rocks that represent earlier mineralizing fluid events. The samples preserve at least three fluid flow pulses since the Eocene and indicate that meteoric fluid has been circulating in the upper crust in the North Anatolian Keirogen since that time.
Speleothem-based stable isotope records are valuable in sub-humid and semi-arid settings where ma... more Speleothem-based stable isotope records are valuable in sub-humid and semi-arid settings where many other terrestrial climate proxies are fragmentary. The Eastern Mediterranean is one such region. Here we present an 80-kyr-long precisely-dated (by U-series) and high-resolution oxygen (δ 18 O) and carbon (δ 13 C) records from Dim Cave (~36°N) in SW Turkey. The glacial-interglacial δ 18 O variations in the Dim Cave speleothem are best explained in terms of changes in the trajectories of winter westerly air masses. These are along a northerly (European) track (isotopically less depleted) during the early last glaciation but are gradually depressed southward closer to the modern westerly track along the North African coast (more depleted) after c.50 kyr and remain in the southern track through the Last Glacial Maximum. The southward displacement of the westerly track reflects growth of the Fennoscandian ice sheet and its impact on westerly wind fields. Changes in δ 13 C are interpreted as reflecting soil organic matter composition and/or thickness. δ 13 C values are significantly more negative in interglacials reflecting active carbonic acid production in the soil and less negative in glacial times reflecting carbonate rock values. Several Heinrich events are recorded in the Dim record indicating intensification of westerly flow across this part of the EM.
The geochemical features of the volatiles dissolved in artesian thermal waters discharged over th... more The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins (Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO 2 up to about 340 mlSTP/L H2O marked by a δ 13 C TDC (Total Dissolved Carbon) ranging from −16.9 to +0.18‰ vs PDB, while CH 4 concentrations vary from 4.4 × 10 −5 to 4.9 mlSTP/L H2O . Helium contents were between 9 and N 2800 times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12 mlSTP/L H2O . Helium isotopic composition was in the 0.02-0.21 Ra range (Ra = air-normalized 3 He/ 4 He ratio). The three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the west-central and hottest part of the GAB despite no evidence of recent volcanism. We found that the partial pressure of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian waters from a vast area of N542,000 km 2 , provide new constraints on volatile injection, and show that fluids' geochemistry can provide additional and independent information on the geo-tectonic settings of the Great Artesian Basin and its geothermal potential.
The Eastern Warburton Basin, Northeast South Australia, features major geophysical anomalies, inc... more The Eastern Warburton Basin, Northeast South Australia, features major geophysical anomalies, including a magnetic high of near-200 nT centred on a~25 km-wide magnetic low (b100 nT), interpreted in terms of a magmatic body below 6 km depth. A distinct seismic tomographic low velocity anomaly may reflect its thick (9.5 km) sedimentary section, high temperatures and possible deep fracturing. Scanning electron microscope (SEM) analyses of granites resolves microbreccia veins consisting of micron-scale particles injected into resorbed quartz grains. Planar and sub-planar elements in quartz grains (Qz/PE) occur in granites, volcanics and sediments of the >30,000 km-large Eastern Warburton Basin. The Qz/PE include multiple intersecting planar to curved sub-planar elements with relic lamellae less than 2 μm wide with spacing of 4-5 μm. Qz/PE are commonly re-deformed, displaying bent and wavy patterns accompanied with fluid inclusions. U-stage measurements of a total of 243 planar sets in 157 quartz grains indicate dominance of ∏{10-12}, ω{10-13} and subsidiary §{11-22}, {22-41}, m{10-11} and x{51-61} planes. Transmission Electron Microscopy (TEM) analysis displays relic narrow ≤1 μm-wide lamellae and relic non-sub grain boundaries where crystal segments maintain optical continuity. Extensive sericite alteration of feldspar suggests hydrothermal alteration to a depth of~500 m below the unconformity which overlies the Qz/PE-bearing Warburton Basin terrain. The data are discussed in terms of (A) Tectonic-metamorphic deformation and (B) impact shock metamorphism producing planar deformation features (Qz/PDF). Deformed Qz/PE are compared to re-deformed Qz/PDFs in the Sudbury, Vredefort, Manicouagan and Charlevoix impact structures. A 4-5 km uplift of the Big Lake Granite Suite during 298-295 Ma is consistent with missing of upper Ordovician to Devonian strata and possible impact rebound. The occurrence of circular seismic tomography anomalies below the east Warburton Basin, the Poolowana Basin and the Woodleigh impact structure signifies a potential diagnostic nature of circular tomographic anomalies.
The discovery of large asteroid impact structures, likely and possible impact structures, onshore... more The discovery of large asteroid impact structures, likely and possible impact structures, onshore and offshore the Australian continent Woodleigh [120 km;~360 Ma], Gnargoo [75 km; Lower Permianupper Cretaceous], Tookoonooka [55-65 km;~125 Ma], Talundilly [~84 km;~125 Ma], Mount Ashmore [N 100 km; end-Eocene] and Warburton twin structures [>400km; pre-end Carboniferous]) requires re-examination of the diagnostic criteria used for their identification. Bouguer anomalies of established impact structures (Chicxulub [170 km; 64.98 ± 0.05 Ma], Woodleigh impact structure and Gnargoo probable impact structure display a unique structural architecture where pre-impact structural ridges are intersected and truncated by the outer ring of the circular structure. Seismic reflection data outline circular central uplift domes, basement plugs and rim synclines. Sharp circular seismic tomography anomalies indicate low velocity columns under both the Woodleigh impact structure and Warburton probable impact, hinting at deep crustal fracturing. Deformed, curved and clouded intra-crystalline planar deformation features in quartz (Qz/PDFs), displaying Miller indices ({10-11}, {10-12}, {10-13}) diagnostic of shock metamorphism, abound around exposed established impact structures (Vredefort [298 km; 2023 ± 4 Ma], Sudbury [~250 km; 1850 ± 3 Ma], Charlevoix [54 km; 342 ± 15 Ma], Manicouagan [100 km; 214 ± 1 Ma])
The Savcili Fault Zone represents one of the most prominent regional-scale intraplate fault syste... more The Savcili Fault Zone represents one of the most prominent regional-scale intraplate fault systems in central Turkey, recording the collisional events following the closure of Neo-Tethys in the eastern Mediterranean region. It consists of anastomosing reverse/thrust faults with WNW-ESE direction that placed rocks of the Central Anatolian Crystalline Complex on Paleogene sedimentary units. Structural measurements and kinematic indicators show that faults within the Savcili Fault Zone (SFZ) have top to the NE and NW sense of brittle deformation. Stable isotope (δ 18 O and δ D) and trace element data indicate that fault gouge illites precipitated from deep basinal brines. These fluids were mobilized during phases of compressional deformation and migrated upward along thrust faults toward shallow brittle deformation zones. Rb-Sr and Ar-Ar geochronology of fault gouges in two cataclastic zones demonstrates age variability for two different dating techniques (Rb-Sr: 40.9 ± 1.5 Ma and 22.9 ± 1.3 Ma; Ar-Ar: 46.45 ± 0.25 Ma and 29.8 ± 0.13 Ma). We argue that Rb-Sr dating provides ages more closely reflecting the timing of fault movements because of potential contamination of illite by excess 40 Ar. Accordingly, the SFZ was active during at least two phases; the middle Eocene and late Oligocene to early Miocene, which is consistent with the relative age constraints suggested by field relationships. Geochronology combined with structural field evidence indicates a rapid change in stress regime from extension to contraction at~40 Ma that continued until at least~23 Ma. Direct dating of brittle faulting provides a prolific approach for determining the absolute timing of tectonic events in areas that have largely relied on indirect information.
The metaluminous Soultz-sous-Forêts monzogranite, France, is highly evolved and contains elevated... more The metaluminous Soultz-sous-Forêts monzogranite, France, is highly evolved and contains elevated concentrations of rare-earth elements (REE), Y and particularly Th. Primary accessory minerals include fluorapatite, allanite-(Ce) and Th-rich titanite. Primary titanite has been altered to anatase + calcite + quartz + synchysite-(Ce) ± bastnaesite-(Ce) or anatase + calcite + quartz + monazite-(Ce) + xenotime-(Y) ± thorite. Fluorocarbonate-bearing assemblages are restricted to those samples exhibiting minor selective alteration, whereas those containing phosphate-rich assemblages formed in pervasively altered samples that have experienced high fluid/rock ratios. Comparative electron-microprobe analysis of primary and hydrothermallyderived accessory phases found middle REE, Y and Th concentrations depleted in synchysite-(Ce) relative to primary titanite. Such depletions are not seen in phosphate-rich samples containing monazite-(Ce) and xenotime-(Y). Variability in elemental concentrations may be attributed to distinct fluid chemistries and hence, lead to differential mobility during alteration. Following previous experimental work and mineralogical observations, the ingress of CO 2 -rich solutions was integral for titanite breakdown and the resultant metasomatic assemblage. The influx of CO 2 -rich fluids concomitantly with chloritisation of biotite produced fluids enriched in FCO 3 − . We, therefore, hypothesise that after the alteration of titanite, remnant HCO 3 − or FCO 3 − -rich fluids were able to mobilise significant proportions of MREE, Y and Th not accommodated into the synchysite-(Ce) structure. Conversely, those samples rich in monazite-(Ce) and xenotime-(Y) retained their REE, Y and Th concentrations due to the presence of aqueous HPO 4 2− derived from apatite dissolution.
Geochronological (U-Pb, U-Th-total Pb, Sm-Nd) and geochemical (REE, 87 Sr/ 86 Sr, δ 18 O, δ 13 C)... more Geochronological (U-Pb, U-Th-total Pb, Sm-Nd) and geochemical (REE, 87 Sr/ 86 Sr, δ 18 O, δ 13 C) tracing of intraplate tectonism and associated fluid flow in the Warburton Basin, Australia
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