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The deep‐seated spontaneous coal‐seam fire occurred in the southwestern part of the Upper Silesian Coal Basin (S Poland), confirmed by oxygenated compounds emission to over‐ and underlying rocks. The fire was dated at 19.2–19.8 Ma using the 39Ar‐40Ar method and palaeomagnetism. It was initiated in the Carpathian foreland thanks to a normal faulting in response to thrust‐loaded deflections of the Carpathian foreland lithosphere during collision of tectonic plates (Alcapa and stable Europe). The orogenic loading caused this normal faulting in the foreland and triggering the flexural mechanism of foredeep subsidence and forebulge uplift. Thanks to the dating of rocks affected by the spontaneous coal fire initiated during the rapid uplift of coal‐bearing rocks, when they became exposed to the aeration zone, the age of these mountain‐building processes in the Carpathians has been precisely defined. [ABSTRACT FROM AUTHOR]

SIMS U‐Pb zircon dating of metaigneous rocks of the Nordbreen Nappe from the West Ny‐Friesland terrane (Eastern Basement Province of Svalbard) yields crystallization ages of 1,761 ± 4 Ma for a felsic metatuff and 1,373 ± 4 Ma for a metagabbro dyke. The Palaeoproterozoic age of the metatuff is similar to previously obtained ages for various felsic rocks from the study area, whereas the Mesoproterozoic age of the metagabbro has not been thus far documented on Svalbard. However, a similar age pattern has been reported from Northeast Greenland. Therefore, we conclude that the West Ny‐Friesland terrane can be correlated with age equivalent units of Northeast Greenland. We also explore similarities and dissimilarities between the study area and other terranes of Svalbard and speculate on regional‐scale correlations. Together, the presented new ages provide critical piercing points in palaeogeographic reconstructions of the relatively poorly understood circum‐Arctic region. [ABSTRACT FROM AUTHOR]

Abstract: The low‐temperature thermal history of the Holy Cross Mountains (HCM) is investigated by apatite fission track and apatite and zircon (U–Th)/He thermochronology. Our results provide constraints on the deformation history of Palaeozoic basement rocks in the transition area from Precambrian to Palaeozoic Europe that are exposed from beneath Permian–Mesozoic sediments within the HCM. Late to post‐Variscan cooling of the Palaeozoic strata from maximum temperatures is shown to be a major feature of the HCM. This cooling likely followed a heating event related to burial and/or hot fluid circulation along the Holy Cross Fault in the late Carboniferous. The central part of the HCM shows a rapid cooling event caused by tectonic inversion, which started in the Late Cretaceous. However, this event was less pronounced in the western margin of the HCM, where slow cooling continued throughout the Mesozoic with only minor acceleration of the cooling rate since the latest Cretaceous. [ABSTRACT FROM AUTHOR]

Abstract: The post‐impact orogenic evolution of the world class Ni–Cu–PGE Sudbury mining camp in Ontario remains poorly understood. New temporal constraints from ore‐controlling, epidote–amphibolite facies shear zones in the heavily mineralised Creighton Mine (Sudbury, South Range) illuminate the complex orogenic history of the Sudbury structure. In situ U–Pb dating of shear‐hosted titanite grains by LA‐ICP‐MS reveals new evidence for shear zone reworking during the Yavapai (ca. 1.77–1.7 Ga), Mazatzalian–Labradorian (1.7–1.6 Ga) and Chieflakian–Pinwarian (1.5–1.4 Ga) accretionary events. The new age data show that the effects of the Penokean orogeny (1.9–1.8 Ga) on the structural architecture of the Sudbury structure have been overestimated. At a regional scale, the new titanite age populations corroborate that the Southern Province of the Canadian Shield documents the same tectonothermal episodes that are recorded along orogenic strike within the accretionary provinces of the Southwestern United States. [ABSTRACT FROM AUTHOR]

Dating the timing of motion on crustal shear zones is of tremendous importance for understanding the assembly of orogenic terranes. This objective is achieved in this paper by combining petrological and structural observations with novel developments in in situ U-Th-Pb geochronology of allanite. A greenschist facies shear zone within the Mont Blanc Massif is documented. Allanite is synkinematic and belongs to the mylonitic assemblage. LA- ICP- MS U-Th-Pb isotope analyses of allanite reveal high contents and highly radiogenic isotopic compositions of the common-Pb component. The use of measured Pb-isotope compositions of associated minerals (feldspars and chlorite) is critical for accurate common-Pb correction, and provides a powerful mechanism for linking allanite growth to the metamorphic assemblage. A mean 208Pb/232Th age of 29.44 ± 0.95 Ma is accordingly taken for synkinematic allanite crystallisation under greenschist facies conditions. This age reflects the timing of the Mont Blanc underthrusting below the Penninic Front and highlights the potential of directly dating deformation with allanite. [ABSTRACT FROM AUTHOR]

The end of the Neoproterozoic is punctuated by glacial deposition, but the chronology of these deposits is hindered presently by the paucity of geochronological data. Here, we present new radiometric dating for the basal Sete Lagoas cap carbonate deposits that overlie glacial units in the São Francisco craton. Six samples from aragonite-pseudomorph crystal-rich facies, showing pristine textures and constant 87Sr/86Sr ratios around 0.7075, yielded a Pb–Pb isochron age of 740 ± 22 Ma, which is interpreted as the depositional age for these remarkably preserved rocks. This age can be used to infer a low-to-moderate palaeolatitude of 20–30° for carbonate (and glacial) deposition. In addition, as it overlaps the ages obtained for the oldest Neoproterozoic glacial successions, our result reinforces the idea of a long-standing ‘Sturtian’ interval, suggesting that this event represents either different discrete glaciations or a protracted event encompassing almost 80 Ma. [ABSTRACT FROM AUTHOR]

In order to decipher the origin of eclogite in the high-P/T Sanbagawa metamorphic belt, SHRIMP U–Pb ages of zircons from quartz-bearing eclogite and associated quartz-rich rock (metasandstone) were determined. One zircon core of the quartz-rich rock yields an extremely old provenance age of 1899 ± 79 Ma, suggesting that the core is of detrital origin. Eight other core ages are in the 148–134 Ma range, and are older than the estimated age for trench sedimentation as indicated by the youngest radiolarian fossil age of 139–135 Ma from the Sanbagawa schists. Ages of metamorphic zircon rims (132–112 Ma) from the quartz-rich rock are consistent with metamorphic zircon ages from the quartz-bearing eclogite, indicating that eclogite facies metamorphism peaked at 120–110 Ma. These new data are consistent with both the Iratsu eclogite body and surrounding highest-grade Sanbagawa schists undergoing coeval subduction-zone metamorphism, and subsequent re-equilibration under epidote amphibolite facies conditions during exhumation. Terra Nova, 00, 1–9, 2004 [ABSTRACT FROM AUTHOR]

The Ericiyes Basin is a trans-tensional basin situated 20 km north of the regional Ecemiş Fault Zone. Recently it has been hypothesized that faulting within the Erciyes Basin links with the Ecemiş Fault Zone further south as part of a regional Central Anatolian Fault Zone. New 40Ar/39Ar dating of volcanic and volcaniclastic rocks adjacent to faults, both along the margins and in the centre of the Erciyes Basin, constrains the timing of basin inception and later faulting. Extensional faulting occurred along the eastern and western margins of the basin during the Early Messinian (latest Miocene). Sinistral and minor normal faulting were active along the axis of the basin during the early Pleistocene. These fault timings are similar to those inferred for the Ecemiş Fault Zone further south, and support the hypothesis that faulting within the Erciyes Basin and the Ecemiş Fault Zone are indeed linked. Terra Nova, 00, 1–9, 2004 [ABSTRACT FROM AUTHOR]

The Re–Os (rhenium–osmium) chronometer applied to molybdenite (MoS2 ) is now demonstrated to be remarkably robust, surviving intense deformation and high-grade thermal metamorphism. Successful dating of molybdenite is dependent on proper preparation of the mineral separate and analysis of a critical quantity of molybdenite, unique to each sample, such that recognized spatial decoupling of 187 Re parent and 187 Os daughter within individual molybdenite crystals is overcome. Highly precise, accurate and reproducible age results are derived through isotope dilution and negative thermal ion mass spectrometry (ID-NTIMS). Spatial decoupling of parent–daughter precludes use of the laser ablation ICP-MS microanalytical technique for Re–Os dating of molybdenite. The use of a reference or control sample is necessary to establish laboratory credibility and for interlaboratory comparisons. The Rb–Sr, K–Ar and 40 Ar/39 Ar chronometers are susceptible to chemical and thermal disturbance, particularly in terranes that have experienced subsequent episodes of hydrothermal/magmatic activity, and therefore should not be used as a basis for establishing accuracy in Re–Os dating of molybdenite, as has been done in the past. Re–Os ages for molybdenite are almost always in agreement with observed geological relationships and, when available, with zircon and titanite U–Pb ages. For terranes experiencing multiple episodes of metamorphism and deformation, molybdenite is not complicated by overgrowths as is common for some minerals used in U–Pb dating (e.g. zircon, monazite, xenotime), nor are Re and Os mobilized beyond the margins of individual crystals during solid-state recrystallization. Moreover, inheritance of older molybdenite cores, incorporation of common Os, and radiogenic Os loss are exceedingly rare, whereas inheritance, common Pb and Pb loss are common... [ABSTRACT FROM AUTHOR]

Two granitoid intrusions within the Bu Khang extensional complex in central Vietnam have been dated by U–Pb and Rb–Sr geochronology. A monazite U–Pb age of 26.0 ± 0.2 (2σ) Myr was obtained for the Bu Khang pluton and 23.7 + 1.6/–1.7 Myr for monazite, allanite and zircon from the Dai Loc intrusion. These ages date crystallization of magmas previously assigned Precambrian to Devonian. Rb–Sr analyses of K-feldspar and biotite fractions from the samples yield ages of 19.8 ± 0.6 (2σ) Myr and 19.6 ± 0.5 Myr, respectively. The thermal history recorded by the different geochronometers implies an average exhumation rate of ∼2 mm yr-1 corresponding to ∼9 km of unroofing. Magmatism was either (i) induced passively by lithospheric thinning driven by changes in regional tectonic stresses, or (ii) triggered actively by an ascending plume. Tertiary exhumation and magmatism documented elsewhere in Indochina (e.g. Ailao Shan-Red River and Wang Chao shear zones) favours a regional tectonic cause for extension and granitoid magmatism in the Bu Khang complex. On the other hand, the presence of an upwelling thermal anomaly since at least 35 Ma, causing mantle melting below Indochina, is supported by shear-wave velocity variations in the mantle, and source geochemistry of both the Bu Khang plutons and the Red River belt intrusions. In either case, Tertiary exhumation of the Bu Khang complex can account for previously undocumented NE–SW-directed extension, which is required in northern Vietnam to account for structural changes related to the opening of the South China Sea. [ABSTRACT FROM AUTHOR]

Fission-track thermochronology has been applied to apatite, zircon and titanite from various depths of the Baltic Shield. Burial due to Sveconorwegian (Grenville) and Caledonian foreland sedimentation is revealed. Titanite and zircon fission-track ages from surface samples (from eastern Sweden) do not vary significantly and average ∼ 850 Myr. It is suggested that Sveconorwegian sediments reached a thickness of at least 8 km in eastern Sweden. Exhumation of these sediments was succeeded by deposition of Lower Palaeozoic cover rocks. Apatite fission-track ages along a transect from SW to NE across the shield, increase from ∼ 300 Myr to ∼ 900 Myr and yield the Phanerozoic history of subsidence and exhumation. Apatite fission tracks, in the basement of the thickest parts of the foreland basin, were totally annealed. These results suggest a > 600 km wide Caledonian foreland basin filled by Devonian sediments that were > 2.5 km thick in southern and western Sweden, thinning to the east (in Finland). [ABSTRACT FROM AUTHOR]