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We dated syntectonic calcites on fault planes from the southern branch of the western North Anatolian fault (NAF) in northern Turkey using U-Th geochronology. We selected strike-slip faults that are kinematically related to the current regional strain field. The isotopic ages cluster around different periods during the past ~700 k.y. The most prominent cluster peak of 510.5 ± 9.5 ka (1σ) is consistent with the maximum cumulative strike-slip offset data and tectonic plate motions measured by GPS data, highlighting the fact that the present configuration of the NAF in the southern Marmara region started at ca. 500 ka or earlier. These new isotopic ages, combined with previous considerations of regional tectonics, reveal that faulting along the western NAF initiated primarily in the southern Marmara region at least a few hundred thousand years earlier than the timing suggested for the northern branch of the western NAF. This study presents an innovative approach to constrain the timing of initiation of currently active fault segments along the NAF in southern Marmara. U-Th geochronology of fault-hosted calcite thus has a wide application in determining absolute ages of fault episodes in wider shear zones along plate boundaries.

Bauxite is the world’s main source of aluminum and typically consists of gibbsite, boehmite, and minor amounts of diaspore. However, bauxite deposits from the North and South China blocks consist mostly of diaspore and associated minerals, including anatase and illite. Much of this illite is authigenic and occurs as three polytypes (1M, 1Md, and 2M1), with Kübler indices ranging from 0.23 to 0.47 indicating precipitation temperatures of 175° to 300°C. The Raman spectra of anatase show an intensity ratio of

Bangong-Nujiang Suture Zone (BNSZ) in central Tibet plays an important role in evaluating the formation and uplift mechanism of Tibetan Plateau. However, its Mesozoic tectonic evolution is ambiguous and intensely debated. In this study, Early Cretacesous adakites and sodium-rich arc rocks are identified in Western Qiangtang (WQ) and Northern Lhasa (NL) sub-terranes. Forty-four adakite samples from both WQ and NL have akin geochemical features, and are derived from partial melting of subducted oceanic crust with amphibole residual. Nineteen sodium-rich samples originated from a mixed source region between crustal sediment and enriched lithospheric mantle. These two parallel arc belts separated by the Bangong-Nujiang Suture Zone (BNSZ) represent the divergent double subduction of the Bangong-Nujiang Tethyan Ocean (BNTO). Combined with the previous studies, our new data suggest three significant magmatic flare-ups at ∼240–140 Ma, 135–105 Ma and 92–60 Ma in the WQ and BNSZ, and two at 135–105 Ma and 92–60 Ma in the NL. These asymmetrical magmatic activities indicate that the southern subduction may have commenced at about 135 Ma and experienced slab breakoff at the latest Early Cretaceous, and the northern subduction could trace back to L-Triassic (228 Ma) and experienced episodic low-angle subduction, slab rollback (190-140 Ma) and oceanic ridge subduction (135-100 Ma). The 100–92 Ma magmatic gap, 92–60 Ma magmatic flare-up and L-Cretaceous angular unconformities indicate that the double-sided subduction of the BNTO resulted in soft collision with oceanic lithosphere detachment.

Methods, Figures S1–S30, and data Tables S1 and S2.

A combined ultrasonic treatment, with de-ionized H2 O, dilute HAc or dilute HCl, of three Mid-Miocene glauconite samples was applied to K–Ar date the different separates in order to compare the results with those obtained by the Rb–Sr method using the same three samples and that were analyzed strictly in the same way. Two aliquots yield opposite elemental and K–Ar trends, which suggests different initial mineral compositions for the various pellets. The K–Ar data of two untreated and leached L7 and L8 aliquots are almost within analytical uncertainty from 17.3 ± 0.6 Ma to 19.6 ± 0.7 Ma (2?), while those of the third L10 sample are slightly higher at 22.1 ± 1.2 Ma (2?). Comparatively, the earlier published Rb–Sr ages of the three untreated samples and of the leached aliquots gave similar data for the L7 aliquots by an isochron at 18.1 ± 3.1 (2?) Ma and for the sample L8 by an isochron with an age of 19.6 ± 1.8 (2?) Ma, while the untreated L10 aliquot yields a very high Rb–Sr date of 42.1 ± 1.6 (2?) Ma. This untreated L10 glauconite fraction contains blödite, a Sr-rich carbonate that impacted the two isotopic systems differently. Generally, dilute HCl or HAc acids dissolve carbonates, sulfates, sulfites and oxides, while they do not affect the clay-type crystals such as glauconites. These soluble minerals can be identified indirectly, as here, by X-ray diffraction and the amounts of leached Na2 O, CaO and Fe2 O3 contents. Together with the leaching of some metallic trace elements, those of NaO confirm the leaching of metals and of blödite that are both hosted by the glauconite pellets. The occurrence of this Sr-enriched mineral explains the age differences of the non-treated aliquots and suggests a systematic leaching of any glauconite separate before isotope determination and, possibly, a comparison of the Rb–Sr and K–Ar results. Ultrasonic shaking appears appropriate for physical disaggregation of any contaminating grains that may remain hosted within the pellets, even after a preliminary H2 O wash, which may dissolve and remove the soluble minerals but not the H2 O-insoluble silicates. The K–Ar study completed here as a complement to a previous Rb–Sr study highlights, again, the importance of the preparation step in isotopic studies of glauconite-type and, by extension, of any clay material, as all occurring minerals can interfere in the final age determinations and, therefore, differently in the mineral assemblages. All those not in isotopic equilibrium need to be removed before analysis, including the soluble Sr or alkali-enriched ones. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. We would like to dedicate cordial thanks to the late Emeritus Professor Dr. Paul Pasteels for having allowed us to complete the Rb?Sr study of three glauconite separates by chemical and K?Ar analyses that became the basis of the present study. Two of us, who knew him for years, would also like to dedicate this, as a token of appreciation, to a very gentle colleague and a highly-respected scientist. Two anonymous reviewers are also sincerely thanked for their remarks, corrections and suggestions that were very useful to improve this presentation. The editorial team is also thanked for efficiency and constant availability during the final proofing round. Conflicts of Interest: The authors declare no conflict of interest.

U-Th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late Quaternary crustal deformations. In this study, for the first time we correlate U-Th ages of travertine deposits in coseismic fissures along the North Anatolian Fault Zone with records of paleoseismological studies supported by historical earthquake catalogued data. U-Th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major Holocene earthquakes. Our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the North Anatolian Fault Zone. The periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies. At least six of the periods correspond to the earthquakes reported in the historical catalogues. The age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern North Anatolian Fault Zone with a mode at 130–330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault. Recorded events in carbonate veins indicate a close-epicenter (d VI) paleoearthquakes. Our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques. This tool has advantages over traditional paleoseismological methods for the understanding of long-term earthquake behavior, particularly for prehistoric late Pleistocene events which cannot be dated easily by traditional paleoseismological methods.

Calcite veins are commonly found at shallow depth (a few metres below the surface) in damage zones of active normal fault systems in southwest Turkey. Although earlier studies demonstrated the link between the vein formation and seismicity, the association of near-surface carbonate precipitation with climate-driven hydrological conditions (water table, amount of precipitation and evaporation, and water discharge) is poorly understood. In this study, using the U/Th dating method we investigate the timing of vein formation and the interrelationship between tectonic and climatic-related hydrological processes. Carbonate precipitation is interpreted to occur as a result of sudden pressure drops and CO2 release after earthquake-induced fracturing. Vein formation mostly occurred during glacial periods, which coincide with slow growth rates and higher oxygen isotope values of speleothems from the Eastern Mediterranean region. We relate these episodes to reduced winter rainfall due to the decrease in westerly flow in SW Turkey. These somewhat drier conditions influenced the chemical composition of circulating water, creating conditions conducive to carbonate precipitation and sealing of damage zones. These conditions also facilitated CO2 accumulation and overpressure build-up in the rupture zones. Failure of the faults resulted in the release of large volumes of CO2-rich fluids and the generation of shallow carbonate veins. It is proposed that during phases of increased winter rainfall CO2 is advected to the surface and discharged as passive degassing when meteoric water circulation is enhanced. While regional tectonics is the ultimate driver of fault activity and fracture formation, climate-driven near-surface hydrological changes may have played an important role in modulating CO2-rich fluid circulation and surface discharge.

Eastern Gondwana was subjected to subduction processes during the Middle-Late Jurassic, but how these processes affected intraplate deformation in eastern Australia is poorly understood. Here we present 40Ar/39Ar, K-Ar, and Rb-Sr geochronological data from illitic clay-bearing fault gouges associated with the northern part of the 200 km long, N-striking, dextral strike-slip, Demon Fault in eastern Australia. We show a major range of geochronological ages at 162.99 ± 0.74–152.1 ± 4.8 Ma, indicating that the Demon Fault was active during the Late Jurassic. This period partially coincides with the Middle-Late Jurassic deposition of widespread ash-fall tuffs in the Clarence-Moreton, Surat, and Eromanga basins. We propose that Middle-Late Jurassic intraplate tectonism in eastern Australia was influenced by subduction processes farther east, which produced extensive calc-alkaline magmatism in New Zealand from ~170 Ma. A global plate reorganisation event, related to the development of Early-Middle Jurassic sea-floor spreading of the Pacific Plate, possibly acted as the driving mechanism responsible for the intensification of magmatism and intraplate faulting in eastern Gondwana.

K-Ar isotopic dating has been applied to alkali-rich nanometer-sized illite separates of bentonites since the late 1990s. In the present study, K-Ar and Rb-Sr isotopic analyses were based on mineralogical determinations and morphological observations of similarly nm-sized separates (

Summary Accurately determining the age of hydrothermal ore deposits is difficult, because of lack of suitable mineral chronometers and techniques. Here we present the first LA-MC-ICPMS U-Pb age of carbonates from hydrothermal Sb deposits. Three stages of hydrothermal carbonates from the giant South China Sb metallogenic belt were identified: (1) pre-ore dolomite (Dol-I), (2) syn-ore calcite (Cal-II), and (3) post-ore calcite (Cal-III). The U and Pb isotopic data show that Cal-II yielded a lower intercept age of 115.3 ± 1.5 Ma (MSWD = 2.0), suggesting a Sb mineralization that corresponds to an extension event occurred during the early Cretaceous in South China. Although Cal-III yielded an age of 60.0 ± 0.9 Ma (MSWD = 1.5), indicating a potential tectonothermal event occurred in this belt during the early Cenozoic. Hence, in situ U-Pb dating of calcite offers a new way to determine the age of hydrothermal ore deposits., Graphical Abstract, Highlights • The syn-ore calcite yielded an in situ U-Pb age of 115.3 ± 1.5 Ma • The South China antimony mineralization occurred during the early Cretaceous • Calcite in situ U-Pb dating can determine the timing of hydrothermal mineralization, Thermochronology; Isotope Geochemistry; Geochemistry Methods; Ore Geochemistry

The extensional Val Roveto Fault, which is the longest exhumed potentially-seismogenic structure of central Apennines, Italy, is examined to constrain earthquake-related fluid circulation and fluid sources within shallow carbonate-hosted faults. The study focuses on fault-related comb and slip-parallel veins that are calcite-filled and cut through the principal surface of the Val Roveto Fault. We observe multiple crack-and-seal events characterized by several veining episodes, probably related to different slip increments along the fault plane. We show that vein calcite precipitated in Late Pleistocene time below the present-day outcrop level at a maximum depth of similar to 350 m and temperatures between 32 and 64 degrees C from meteoric-derived fluids modified by reactions with crustal rocks and with a mantle contribution (up to similar to 39%). The observed warm temperatures are not compatible with a shallow (

Sequential leaching was completed by successive interactions of ultra-pure H2O, HAc, HCl and HNO3 with silicified/carbonated Archaean whole rocks from Barberton Greenstone belt of South Africa. The purpose of this experiment was an identification of the minerals interacting with each reagent and, therefore, a detailed succession of isotopically dated tectonic-thermal episodes recorded in these minerals. The contents of the major, trace and rare-earth elemental, together with the Sr, Nd and Pb isotopic compositions of untreated, leachate and residue triplets allowed identification and analysis of various types of carbonates and sulfates mixed with insoluble silicates. The samples yield two overall geological age milestones at 2.9 ± 0.1 and 2.1 ± 0.1 Ga, as well as varied age values, some with large uncertainties. A further event at about 1.6 ± 0.1 Ga is suggested probably in relation with the emplacement of the Bushveld complex or of further intrusive complexes of the Kaapvaal Craton. While the basics of the different used isotopic systems can be considered to be similar, the Rb-Sr method appears to be the best suited to detail the studied rocks, especially their sensitive soluble minerals. The Sm-Nd method is less flexible because of its inherent need of widely ranging Sm/Nd ratios that depend on the mineral assemblage. In the case of the Rb-Sr ages well constrained by isochron arrays, more similar ages were obtained by tentatively called isotrends that consist in data points slightly scattered along the arrays giving higher uncertainties, especially with the Sm-Nd method. The fact that these isotrends gave similar ages in addition to those of the isochrons comforts the historic evolution of the studied material. These scatters most probably correspond to slight changes in the chemical characteristics of minerals leached by the successive reagents, but analytical uncertainties cannot be completely excluded, especially in the case of the HNO3 leaching step. Finally, the Pb-Pb method appears to be of a more limited application, possibly because of possible metal contamination of the host rocks, either during their evolution in a region characterized by metal-rich concentrations or more recently during discrete surficial to sub-surficial alteration/weathering processes. In terms of leaching efficiency, that with H2O removed expectedly the lowest amounts of soluble components followed by HNO3, the two efficient removers being dilute HAc and HCl. In turn, the obtained geochronological ages consolidate previously published ages that concentrate on post-depositional tectonic-thermal events within the Kaapvaal Craton during about 1.0 Ga. However, they also suggest some reconsideration for other ages of the literature.

Central Anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back-arc extension generating non-uniformly distributed stress fields. In this study, we provide direct field evidence of various stress directions and investigate carbonate-filled fracture systems in the Central Anatolian Volcanic Province using U/Th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress. Field data reveal two independent fracture systems in the region. Successive fracture development has been controlled by two different volcanic eruption centers (Hasandag Composite Volcano and Acigol Caldera). Trace element, and stable (C and O) and radiogenic (Sr) isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems. The U/Th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka. The NNE-trending first fracture system was formed as a result of strain cycles in a period from 149 +/- 2.5, through 91 +/- 1.5 to 83 +/- 2.5 ka BP. Subsequent deformation events represented by the ENE-trending second fracture zone have been triggered during the period of 53 +/- 3.5, 44 +/- 0.6 and 34 +/- 1 ka BP before the first fracture zone resumed the activity at about 4.7 +/- 0.15 ka BP. Although further studies are needed to evaluate statistical significance of age correlations, the periods of carbonate precipitation inferred from U-Th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events. (C) 2017 Elsevier Ltd. All rights reserved.

The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. 87Sr/86Sri = 0.7042–0.7044, 143Nd/144Ndi = 0.5128–0.5129, 206Pb/204Pbi = 18.90–18.94, eHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker [Ts/(Ts + Tm)] all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process.

Cappadocia Geothermal Province (CGP), central Turkey, consists of nine individual geothermal regions controlled by active regional fault systems. This paper examines the age dating of alteration minerals and the geochemistry (trace elements and isotopes) of the alteration minerals and geothermal waters, to assess the evolution of CGP in relation to regional tectonics. Ar–Ar age data of jarosite and alunite show that the host rocks were exposed to oxidizing conditions near the Earth’s surface at about 5.30 Ma. Based on the δ18O–δD relationhip, water samples had a high altitude meteoric origin. The δ34S values of jarosite and alunite indicate that water samples from the southern part of the study area reached the surface after circulation through volcanic rocks, while northern samples had traveled to the surface after interacting with evaporates at greater depths. REY (rare earth elements and yttrium) diagrams of alteration minerals (especially illite, jarosite and alunite) from rock samples, taken from the same locations as the water samples, display a similar REY pattern to water samples. This suggests that thermal fluids, which reached the surface along a fault zone and caused the mineral alteration in the past, had similar chemical composition to the current geothermal water. The geothermal conceptual model, which defines a volcanically heated reservoir and cap rocks, suggests there are no structural drawbacks to the use of the CGP geothermal system as a resource. However, fluid is insufficient to drive the geothermal system as a result of scanty supply of meteoric water due to evaporation significantly exceeding rainfall.

Australian terranes concealed beneath Mesozoic cover record complex Precambrian tectonic histories involving a successive development of several Proterozoic to Palaeozoic orogenic systems. This study presents an integrated approach combining K–Ar, 40Ar–39Ar, and Rb–Sr geochronologies of Precambrian authigenic illites from the recently discovered Millungera Basin in north-central Australia. Brittle deformation and repeated fault activity are evident from the sampled cores and their microstructures, probably associated with the large-scale faults inferred from interpretations of seismic surveys. Rb–Sr isochron, 40Ar–39Ar total gas, and K–Ar ages are largely consistent in indicating late Mesoproterozoic and early Proterozoic episodes (∼1115±26, ∼ 1070±25, ∼1040±24, ∼1000±23, and ∼905±21 Ma) of active tectonics in north-central Australia. K–Ar results show that illites from fault gouges and authigenic matrix illites in undeformed adjacent sandstones precipitated contemporaneously, indicating that advection of tectonically mobilized fluids extended into the undeformed wall rocks above or below the fracture and shear (fault gouge) zones. Isotopic age data clearly indicate a Mesoproterozoic minimum age for the Millungera Basin and thus previously unrecorded late Mesoproterozoic–early Neoproterozoic tectonic events in north-central Australia. This study provides insight into the enigmatic time–space distribution of Precambrian tectonic zones in central Australia, which are responsible for the formation of a number of sedimentary basins with significant energy and mineral resources.

We investigate the temporal variations in stable carbon and oxygen and radiogenic Sr isotope as well as rare earth element contents of Akkaya travertine deposits in the Eskipazar region, northwest Turkey. U-Th age data indicate that studied travertines in the periphery of the 1944-earthquake rupture of the North Anatolian Fault Zone formed in a time span of 93 to 1.8 ka BP. The younger group is represented by fissure-filling carbonates whereas the older sequence is composed of veins with varying crystallization ages that are injected to bedded travertines. The age data on vein injections and fissure-ridge travertines in the Akkaya site indicate the seismic reactivation along the west-central part of the North Anatolian Fault Zone to be intensified at least 4 periods (1.8, 20, 47 and 88 ka BP) during the last 90 ka. δ18O and δ13C systematics of Akkaya travertines, which are precipitated by CO2–rich fluids depressurized during episodic seismic unrest, are in the range from −15.86 to −7.67‰ (VPDB) and 4.66–8.68‰ (VPDB), respectively. δ18O of the fluid equilibrating with the studied travertines is estimated in the range of −11.2 to −10.2‰ which is quite consistent with the average value (−12.3‰) reported for the Akkaya thermal spring. Stable isotope values of travertines indicate modification by rapid CO2 degassing associated with seismic events. Helium isotope compositions of gas phase and dissolved gas of thermal fluids in the area refer to mantle contribution up to 12 %. Sr isotope values of Akkaya travertines are probably originated from Upper Cretaceous marine limestones or mafic basement rocks. REY contents are about 3 orders of magnitude lower than those of basement lithologies.

The interior of the Australian continent shows evidence for late Quaternary to Recent fault-controlled mantle 3 He and CO 2 degassing. A series of interconnected NW-striking sinistral faults, the Norwest fault zone (NFZ), in south-central Australia are associated with travertine mounds, the latter show a regular spacing of 50–70 km. U-series ages on 26 samples range from 354 ± 7 to 1.19 ± 0.02 ka (2 σ errors) and suggest a clustering every ∼3–4 ka since ∼26 ka. Geochemical data demonstrate a remarkable mantle-to-groundwater connection. Isotopic data indicate that the groundwater is circulating to depths >3 km and interacting with Neoproterozoic/Cambrian basement and mantle volatiles. 3 He/ 4 He isotope ratios show that the He comes in part from the mantle. This demonstrates that the NFZ cuts through the entire crust and provides pathways for mantle degassing. Scaling relationships suggest that the series of sinistral faults that make up the NFZ are interconnected at depths and have a significant strike length of 60–70 km or more. The NFZ occurs where a major compositional boundary and a significant heat flow anomaly occurs, and a major step in lithospheric thickness has been mapped. We discuss a tectonic model in which recent stress field, heat flow and lithospheric structure in central Australia reactivated a set of steeply dipping Neoproterozoic faults, which may now be growing into a crustal/lithospheric-scale structure.

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 CO2-bearing fluids responsible for the carbonate precipitation. δ18OVPDB and δ13CVPDB values of the calcite veins range between −5.9 and −1.7‰, and −10.6 and −4.6‰, 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 CO2 degassing events associated with seismic and aseismic deformation. Oxygen and Sr isotope compositions (δ18OVPDB: −5.9 to −1.7‰; 87Sr/86Sr: 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 CO2 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 EuPAAS 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 CO2 accumulations.

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 δ18O and δ13C 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), 87Sr/86Sr ratios, calcite micromorphology, and growth rates. Increasing concentrations of Y, Zr (and U) and elevated 87Sr/86Sr ratios are attributed to enhanced levels of terrestrial input during these periods. Correlations between δ13C, δ18O 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 dolomite 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.

The history of thermal and fluid flow events is of crucial importance to understand the mechanism of hydrocarbon maturation. The northern South China Sea (SCS) contains abundant hydrocarbon resources with high heat flow anomalies, but the mechanisms responsible for modification of thermal regimes are poorly understood. Here we conducted the first high-precision Rb-Sr isochron dating and geochemical analyses of authigenic illites separated from the Palaeogene sandstones in the Beibuwan Basin, northern SCS. Eight high-precision Rb-Sr isochron ages reveal three major thermal and fluid flow events in the Beibuwan Basin, northern SCS. The 34.5 ± 0.9 Ma and 23.6 ± 0.8 Ma events occurred in the western area are probably related to the Eocene-Oligocene transition characterised by a significant regional unconformity resulted from intensive uplift of Hainan Uplift and Oligocene-Miocene transition marked by a post-rift unconformity, respectively. By contrast, the 31.2 ± 0.6 Ma event affecting the eastern area appears to be closely associated with the igneous intrusion dated by zircon U/Pb to 32.3 ± 0.7 Ma. REE and stable isotope characteristics indicate that the illites from the western area formed within a meteoric-hydrothermal system, whilst those from the eastern area were likely precipitated from fluids heated by the large-scale igneous intrusion at higher water/rock ratios. Moreover, our data in conjunction with palaeo-temperature reconstructions show that the fluid flow events had profound effects on the rapid organic maturation in the northern SCS.

In the easternmost segment of the North Anatolian Fault (NAF) zone there are discrepancies in earthquake characteristics arising from differences between geodetically determined and geologically observed slip rates. We investigated the spatial distribution of deformation across a NAF fault segment, Turkey. Field observations were conducted on the offset of physiographic features along the principle fault and on a carbonate-filled fissure system a few hundred meters away from the main slip zone. Considering the rheology of the geological units, we propose distributed deformation across the principal fault strand in a stretching zone causing sigmoidal simple-shear rotation of the carbonate-filled fissure system. Since the fissure system is made up by previously dated alternating carbonate bands formed during distinct rupture events, the sigmoidal deformation provides an opportunity to understand the off-fault deformation rate in the stretching zone. Comparing displacement data of the sigmoidal carbonate vein with isotopic age results indicates an off-fault deformation of 15.72±2.83 mm per year for the Holocene, which corresponds to at least 50% of the geodetically estimated annual slip across the fault. The results indicate that distributed deformation needs to be taken into account in terms of the discrepancies on earthquake characteristics of active fault systems.

The understanding of the relationship between the geochemistry of fluids circulating during travertine deposition and the presence of active faults is crucial for evaluating the seismogenetic potential of an area. Here we investigate travertines from Pamukkale and Resadiye (Turkey), sited in seismic regions and next to thermal springs. These travertines formed similar to 24,500-50,000 (Pamukkale) and similar to 240-14,600 years (Resadiye) BP. We characterize fluid inclusions (FIs) and studied concentration of H2O, CO2, O-2 + N-2, and He-3, He-4, Ne-20, and Ar-40, and bulk composition (trace elements and delta C-13-delta O-18). FIs from both localities are mainly primary with low salinity and homogenization temperature around 136-140 degrees C. H2O is the major component followed by CO2, with the highest gas content measured in Pamukkale travertines. Concentrations of Ne-Ar together with O-2 + N-2 indicate that travertines from both areas precipitated from atmosphere-derived fluids. The He-3/He-4 is 0.5-1.3 Ra in Pamukkale and 0.9-4.4 Ra in Resadiye. Samples with R/Ra > 1 are modified by cosmogenic He-3 addition during exposure to cosmic rays. Excluding these data, FIs of Resadiye are mostly atmosphere-derived. This implies a shallow formation where the circulation was dominated by meteoric waters, which is consistent with their young age. Instead, FIs of Pamukkale show mixing of mantle-, crustal-, and atmosphere-derived He, indicating that these travertines formed in lithospheric fractures. Based on the delta C-13(CO2) and delta O-18 of bulk rocks, we infer that travertines formed involving crustal- (mechanochemical rather than organic) and mantle-derived CO2. Trace elements of Pamukkale and Resadiye show comparable rare earth element patterns. We conclude that travertines formed in response of seismogenetic activity.

Çöpler porfiri-epitermal altın yatağı, Tetis Alpin-Himalaya orojenik kuşağında açılmalı tektonizma sonucugelişen orta Eosen yaşlı plütonik sokulumlarla ilişkili bir altın yatağıdır. Plütonik kayaçlar (granodiyorit porfir, diyorit porfir) Geç Paleozoyik-Mesozoyik yaşlı metapelit ve metakarbonat kayaçlar içerisine sokulum yaparak porfiri-epitermal bir Cu-Au yatağı oluşturmuş ve hidrotermal alterasyon zonlarının (potasik, fillik, propilitik, arjilik) gelişimine neden olmuştur. Bu çalışmada, önceki araştırmacılarca yerel ve sınırlı alanda geliştiği belirtilen süperjen alterasyonun aksine, geniş yayılım sunan arjilik alterasyon zonlarının mineralojik-petrografik özelliklerinin ortayakonulması amaçlanmıştır. Bu kapsamda, optik ve taramalı elektron mikroskop (SEM ve SEM-EDS), X-ışınları kırınımı (XRD), O-H izotop jeokimyası ve K/Ar yaş tayini incelemeleri gerçekleştirilmiştir. Aşırı killeşmiş granodiyorit porfirlerde bile, ilksel porfiritik doku izlenebilmekte, ince-kristalli kil ve kuvarslar homojen ve yer yer mikrolaminasyonlar şeklinde gözlenmektedir. Simektit ve karışık-tabakalı illit-simektit (I-S) mineralleri yapraksıtüysü,illit ve kaolinitler levhamsı biçimler sergilemektedir. Kuvars ve jarositler özşekilli kristaller, kristobalitlerkurtçuk görünümlü, bu çalışmada ilk kez belirlenen krandallitler ise ince-taneli granüler topluluklar şeklinde gözlenmektedir. Arjilik zona ait örnekler fillik zona yakın iç kesimlerde (ileri arjilik zon) kuvars + I-S, kuvars + krandallit + jarosit ve kristobalit, dış kesimlerde (arjilik zon) ise kuvars + simektit + kaolinit birliktelikleri sergilemektedir. Simektitler dioktahedralbileşime sahiptir (d060

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 (δD) and 40Ar/39Ar 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 δD 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). δD values of the authigenic illite population, obtained by extrapolation, are −89 ± 3‰, −90 ± 2‰, and −97 ± 2‰ (VSMOW) for samples KSL, RES4-1, and G1G2, respectively. These correspond to δD fluid values of −62‰ to −85‰ for the temperature range of 125°C ± 25°, indistinguishable from present-day precipitation values. δD values of the detrital illite population are −45 ± 13‰, −60 ± 6‰, and −64 ± 6‰ for samples KSL, G1G2, and RES4-1, respectively. Corresponding δD fluid values at 300°C are −26‰ to −45‰ and match values from adjacent metamorphic terranes. Corresponding clay gouge ages are 41.4 ± 3.4 Ma (authigenic) and 95.8 ± 7.7 Ma (detrital) for sample G2 and 24.6 ± 1.6 Ma (authigenic) and 96.5 ± 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.

The Warburton–Cooper–Eromanga basins of central–eastern Australia contain a number of reactivated fracture–fault networks that relate to a complex and poorly understood thermal and tectonic evolution. Authigenic illite was sampled from two prominent features of the Warburton–Cooper basins: the Gidgealpa–Merrimelia–Innamincka Ridge, composed of anticlinal imbricate thrust fault blocks, and the synclinal Nappamerri Trough. These sample sets were investigated using a combination of clay mineralogical, trace element and stable isotope analyses to deduce the palaeofluid chemistry associated with past tectonothermal perturbations. The Nappamerri Trough hosts the highly radiogenic Big Lake Suite granite and part of one of Australia’s larger on-shore oil and gas reserves. Calculated fluid stable isotope values from the trough, in conjunction with calculated palaeotemperatures, indicate an influx of evolved high-latitudinal meteoric waters under an extremely high geothermal gradient (∼100 °C km −1 ) and high water/rock ratios consistent with an extensional environment. Such high water/rock ratios resulted in intense alteration of the granite during which it underwent substantial enrichment in the heat-producing elements (HPE), particularly Th. This hydrothermal system is interpreted to result from continent-wide transmission of tensional stress originating from episodic rifting of the eastern Australian margin in the mid Cretaceous, as dated by Sm–Nd, Rb–Sr and Ar–Ar. The Gidgealpa–Merrimelia–Innamincka Ridge, by contrast, is marked by a lower, but still elevated, palaeogeothermal gradient (∼42 °C km −1 ) and calculated fluid isotopic values compatible with evolved basinal fluids of meteoric origin under low water/rock ratio conditions. Distinct trace element compositions of residue and leachate aliquots further indicate two periods of fluid flow with unique chemical compositions. In light of previous geochronology, these events are interpreted as westward extensions of widespread crustal tensional stress that affected much of central and eastern Queensland in the Carboniferous and Late Triassic. Integrated analyses of authigenic illite provide evidence for three periods of fluid flow and elevated thermal regime associated with regional tectonism during the Carboniferous, Late Triassic and Cretaceous. Our data further show that due to the extremely high geothermal gradient and water/rock ratios, Cretaceous fluid flow had profound effects on the surrounding geology, which may have formed/enhanced two of Australia’s most significant energy resources.

The Proterozoic (~1.43 Ga) Velkerri Formation (McArthur Basin, Northern Territory) is believed to host one of the world’s oldest petroleum systems. Drilling and production tests demonstrated the encouraging potential of this unconventional gas resource and current efforts are aimed at better defining the extent of the gas and liquid-rich portions of this shale play. In this context, we conducted a comprehensive characterisation of specimens from the Amungee Member of the Velkerri Formation (previously referred to as the Middle Velkerri) sampled along a thermal maturity gradient from wells drilled across the Beetaloo Sub-basin. The scope of our analysis was to shed light on how the organic matter in the Velkerri Formation is affected by thermal maturity and how this affects the pore structure of the host rock. To this end, we integrated light and electron microscopy imaging with Raman spectroscopy and pyrolysis techniques to define the maturity of the sediments and visualise the shale pore network. In concert with the direct imaging, bulk samples were experimentally tested to measure their gas permeability and gas adsorption capacity. The results indicate that porosity is mostly organic-hosted with pore size dominated by meso- and micro-pores (i.e.

Widespread travertine deposits occur in the southwestern Great Artesian Basin (GAB) in central Australia. Priestley et al. (2018) reported uranium-series ages of travertine deposits and concluded that elevated travertine deposition rates are synchronous with wet periods and that times of travertine deposition represent times of high regional rainfall. We propose an alternative explanation that CO2 degassing from the mantle associated with active faulting played a major role in travertine precipitation in the southwestern GAB.

The Warburton-Cooper basins, central Australia, include a multitude of reactivated fracture-fault networks related to a complex, and poorly understood, tectonic evolution. We investigated authigenic illites from a granitic intrusion and sedimentary rocks associated with prominent structural features (Gidgealpa-Merrimelia-Innamincka Ridge and the Nappamerri Trough). These were analysed by 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd geochronology to explore the thermal and tectonic histories of central Australian basins. The combined age data provide evidence for three major periods of fault reactivation throughout the Phanerozoic. While Carboniferous (323.3 ± 9.4 Ma) and Late Triassic ages (201.7 ± 9.3 Ma) derive from basin-wide hydrothermal circulation, Cretaceous ages (~128 to ~86 Ma) reflect episodic fluid flow events restricted to the synclinal Nappamerri Trough. Such events result from regional extensional tectonism derived from the transferral of far-field stresses to mechanically and thermally weakened regions of the Australian continent. Specifically, Cretaceous ages reflect continent-wide transmission of tensional stress from a > 2500 km long rifting event on the Eastern (and southern) Australian margin associated with break-up of Gondwana and opening of the Tasman Sea. By integrating 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd dating, this study highlights the use of authigenic illite in temporally constraining the tectonic evolution of intracontinental basins that would otherwise remain unknown. Furthermore, combining Sr- and Ar-isotopic systems enables more accurate dating of authigenesis whilst significantly reducing geochemical pitfalls commonly associated with these radioisotopic dating methods.

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 Permian - upper Cretaceous], Tookoonooka [55-65. km; ~. 125. Ma], Talundilly [~. 84. km; ~. 125. Ma], Mount Ashmore [>. 100. km; end-Eocene] and Warburton twin structures [>. 400. km; 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]), Tookoonooka and Talundilly). Deformed Qz/PDFs allow recognition of shock metamorphism in buried impact structures, where original Qz/PDFs were bent, recrystallized and/or clouded during formation of the central uplift and hydrothermal activity triggered by the impact. Planar deformation in quartz can also occur in explosive pyroclastic units but are limited to Boehm lamella (Brazil twins) with single lamella sets {0001}. It has been suggested that a class of microstructures in quartz, referred to as metamorphic deformation lamella (Qz/MDL), occur in endogenic tectonic-metamorphic terrains. However, no type locality has been established for Qz/MDL of non-impact origin.

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 ( 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.

We report two Ar-40/Ar-39 illite ages from fault gouge directly above the current trace of the Alpine Fault in New Zealand at Gaunt Creek (1.36 +/- 0.27 Ma) and Harold Creek (1.18 +/- 0.47 Ma), and one Ar-40/Ar-39 illite age from fault gouge from the Two Thumbs Fault on the east side of the Southern Alps. Metamorphic muscovite clasts inherited into the Alpine Fault gouge yielded Ar-40/Ar-39 ages of 2.04 +/- 0.3 Ma at Gaunt Creek and 11.46 +/- 0.47 Ma at Harold Creek. We also report Rb-Sr muscovite-based multimineral ages of Alpine Schist mylonite adjacent to the dated fault gouge at Harold Creek (13.1 +/- 43 Ma) and Gaunt Creek (8.9 +/- 3.2 Ma). Ar-40/Ar-39 muscovite ages from the Gaunt Creek mylonite yielded plateau ages of 1.47 +/- 0.08 Ma and 1.57 +/- 0.15 Ma. Finally, we report zircon fission track (0.79 +/- 0.11 and 0.81 +/- 0.17 Ma) and zircon (U-Th)/He ages (0.35 +/- 0.03 and 0.4 +/- 0.06 Ma) from Harold Creek.& para;& para;We interpret the fault gouge ages to date growth of newly formed illite during gouge formation at temperatures of similar to 300-350 degrees C towards the base of the seismogenic zone. Simple backcalculation using current uplift/exhumation and convergence rates, and dip angles of 45-60 degrees at the Alpine Fault support that interpretation. We infer that the fault gouge ages record faulting and gouge formation as the rocks passed very rapidly through the brittle-ductile transition zone on their way to the surface. Rb-Sr and Ar-40/Ar-39 ages on muscovite from Alpine Schist mylonite date muscovite growth at similar to 11 Ma together with a younger phase of cooling/shearing at similar to 1.5-2 Ma. Our ages from the Alpine Schist indicate extremely rapid cooling exceeding 200 degrees C/Ma. The fault gouge age from the Two Thumbs Fault is significantly too old to have formed as part of the late Neogene/Quaternary Southern Alps evolution. Crown Copyright (C) 2017 Published by Elsevier B.V. Ail rights reserved.

The metaluminous Soultz-sous-Forets 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 hydrothermally-derived 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 CO2-rich solutions was integral for titanite breakdown and the resultant metasomatic assemblage. The influx of CO2-rich fluids concomitantly with chloritisation of biotite produced fluids enriched in FCO3−. We, therefore, hypothesise that after the alteration of titanite, remnant HCO3− or FCO3−-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 HPO42− derived from apatite dissolution.

The emplacement of calcite-filled veins perpendicular to the Dead Sea Fault Zone in northern Israel reflects strain partitioning during transpression. We present structural, geochemical, and U–Th geochronological data that constrain the mechanism, conditions and timing of vein formation. Vein walls are strongly brecciated and commonly cemented with coarsely crystalline calcite, whereas calcite-filled veins are composed of wall-parallel bands of calcite crystals. Elongated blocky and fibrous calcite crystals grew perpendicular to the vein walls and are characterised by a truncate sealing-hiatus morphology, indicating episodes of partial or complete sealing of the fractures during calcite precipitation. Stable isotope and rare-earth element and yttrium (REY) analyses indicate that calcite-filled veins precipitated by karst processes, involving meteoric water and limited fluid-rock interactions. U–Th dating results show a prolonged history of vein growth. While some veins initiated prior to 500 ka, the majority of the veins were active between 358 and 17 ka. Age constraints on vein activity correspond to an ∼E–W regional shortening phase in this sector of the Dead Sea Fault Zone, associated with an increased component of convergence during the late-Pleistocene.

The Early–mid Cretaceous marks the confluence of three major continental-scale events in eastern Gondwana: (1) the emplacement of a Silicic Large Igneous Province (LIP) near the continental margin; (2) the volcaniclastic fill, transgression and regression of a major epicontinental seaway developed over at least a quarter of the Australian continent; and (3) epeirogenic uplift, exhumation and continental rupturing culminating in the opening of the Tasman Basin c. 84 Ma. The Whitsunday Silicic LIP event had widespread impact, producing both substantial extrusive volumes of dominantly silicic pyroclastic material and coeval first-cycle volcanogenic sediment that accumulated within many eastern Australian sedimentary basins, and principally in the Great Australian Basin system (>2 Mkm3 combined volume). The final pulse of volcanism and volcanogenic sedimentation at c. 105–95 Ma coincided with epicontinental seaway regression, which shows a lack of correspondence with the global sea-level curve, and alternatively records a wider, continental-scale effect of volcanism and rift tectonism. Widespread igneous underplating related to this LIP event is evident from high paleogeothermal gradients and regional hydrothermal fluid flow detectable in the shallow crust and over a broad region. Enhanced CO2 fluxing through sedimentary basins also records indirectly, large-scale, LIP-related mafic underplating. A discrete episode of rapid crustal cooling and exhumation began c. 100–90 Ma along the length of the eastern Australian margin, related to an enhanced phase of continental rifting that was largely amagmatic, and probably a switch from wide–more narrow rift modes. Along-margin variations in detachment fault architecture produced narrow (SE Australia) and wide continental margins with marginal, submerged continental plateaux (NE Australia). Long-lived NE-trending cross-orogen lineaments controlled the switch from narrow to wide continental margin geometries.

Intensive carbonate and clay mineral authigenesis took place throughout the Late Permian Bowen-Gunnedah-Sydney basin system in eastern Australia. We conducted isotopic and trace element analyses of carbonate and clay minerals from clastic sedimentary rocks of the Gunnedah Basin and the Denison Trough in the Bowen Basin. Rb-Sr isochron age data of the illitic clays are consistent with episodic hydrothermal fluid flow events that occurred in association with Gondwana rifting accompanied by alkaline magmatism at similar to 85 Ma and similar to 95 Ma. Stable isotope data of carbonate and clay minerals from the Gunnedah Basin are indicative of meteoric waters from a high-latitude environment as the main fluid source, whereas trace element, Sr and Nd isotope data highlight mixing of meteoric fluids with magmatic and/or crustal components, with a possible input from marine carbonates for some samples. Trace metals, oxygen and strontium isotopes of dawsonites from the Denison Trough are interpreted to have been mobilised by fluids that interacted with evolved clastic sedimentary and marine carbonate end members. According to the carbon isotope data, CO2 for calcite and ankerite precipitation was sourced mainly from thermal degradation of organic matter and magmatism, whereas the CO2 used for dawsonite formation is inferred to have been derived from magmatic and marine sources. In the low permeability environments (particularly in coal seams), the increasing accumulation and oversaturation of CO2 particularly promote the precipitation of dawsonite. (C) 2011 Elsevier Ltd. All rights reserved.