Type and amount of sediment generation are intimately connected to tectonic and climatic processes active at the earth's surface today as well as throughout the geologic past. Detrital single grains ...(sand to very coarse silt sized) from well-dated sedimentary formations serve as mineral tracers in sedimentary systems and record the sediment-forming processes. In this review, a selection of individual methods available to extract petrogenetic and chronological information from detrital mineral grains is compiled. Emphasis is placed on techniques, concepts, and their possibilities and shortcomings in defining the type and geologic history of source rocks, as well as the rates and relative proportions at which sediments are being eroded and delivered to basins. Statistical issues intrinsically coupled to the interpretation of detrital single-grain distributions are highlighted, as well as new emerging techniques. These include geochronology of phases like e.g. titanite, monazite, or rutile to overcome the common restriction to apatite or zircon bearing lithologies, as well as any kind of double or triple dating to extract both high-T and low-T thermochronological information from the very same detrital grains. Mineral pairs are especially suited to quantify the relative contributions of well-defined source rocks or areas to the sediment when the two phases (i) occur in contrasting rock types, (ii) are relatively stable under sedimentary conditions, and (iii) allow for extracting significant and detailed information on source rock petrology and chronology. In general, however, multi-method approaches are the only way to overcome ambiguous information from the sedimentary record. In combination with either independent information on sediment flux or erosion rates derived from single-grain thermochronology, the sediment-forming processes as well as their controlling mechanisms and overall geologic settings can be properly assessed.
Xenoliths recovered from the post-Variscan Bode dike system of the eastern Harz Mountains provide evidence for the existence of an Early Devonian magmatic arc system hidden beneath very low-grade ...metasedimentary rocks of the Rhenohercynian Zone, but also for Late Carboniferous–Early Permian crust reworking. This interpretation is based on petrographic observations and whole-rock geochemical analyses of granite xenoliths, in addition to results of zircon U–Pb dating and Hf isotope analyses. Zircon grains recovered from variably deformed granite xenoliths yield ages between 419 and 393 Ma, interpreted to reflect the timing of granite intrusion. Rare zircon xenocrysts of Archean (ca. 2.92–2.65 Ga) and Proterozoic age (ca. 1.5 to 0.56 Ga), all with subchondritic εHf
420 Ma
values (− 0.8 to − 5.5) indicate reworking of older crust. Compilation of age-Hf isotope data further suggests that the pre-Variscan granitoids beneath the Harz Mountains belong to the same magmatic arc system exposed widespread in the adjacent Mid-German Crystalline Zone, and interpreted to result from NW-ward subduction of the Rheic Ocean beneath Avalonia-Baltica. Zircon in xenoliths with granophyric texture yields ages at 400 Ma and 295–310 Ma, indicating re-melting of Devonian granitoid basement during post-Variscan rift-related magmatism, immediately prior to Bode dike intrusion.
Graphical abstract
Left: Late Devonian intrusion of magmatic arc granites during NW-ward subduction of the Rheic ocean beneath Avalonia-Baltica. Right: Formation of the Bode dike system and Harz granites during Late Carboniferous-Permian extension.
The estimation of the peak metamorphic temperature by Raman spectroscopy of carbonaceous material (RSCM) is influenced by several bias sources grouped in measuring conditions, spectral processing and ...sample heterogeneity. The measuring conditions (selected excitation wavelength) and the operator bias during spectral processing have a pronounced impact on the temperature estimate and thus on the comparability and portability of thermometric data obtained by RSCM. Several calibration lines of RSCM geothermometers are published already, but no standardised approach exists. Samples of carbonaceous material bearing metasediments with well‐established metamorphic conditions of the central and western Alps compile a reference series. By applying an automated, iterative and randomised curve‐fitting approach, a consistent and user input‐independent RSCM geothermometer is presented, which covers peak metamorphic temperatures from ca. 160 to 600 °C. The method is hardware independent because the measuring conditions bias is excluded by the use of the reference series and the automated curve‐fitting approach reduces the spectral processing bias effectively, increasing the method's comparability and portability. By distributing the reference series and the automated curve‐fitting software, a laboratory will be able to derive a laboratory specific calibration line for the RSCM geothermometer.
Key Points
Based on a novel evaluation scheme and a reference series a standardized methodology to RSCM geothermometry is presented.
The Scaled Total Area (STA)‐RSCM approach will increase the comparability of RSCM geothermometric data.
The STA‐RSCM approach provides a continuous geothermometer from ca. 160 to 600 °C
Understanding the physical basics of tectonic events, related fluid flow and ore deposition represents one of the great challenges in modern geosciences. In this contribution, Sm-Nd ages of ...hydrothermal fluorites and U-Pb ages of carbonates and iron oxides from unconformity-related vein type deposits in the Schwarzwald next to the Upper Rhinegraben rift in SW Germany are used to distinguish different pulses of hydrothermal fluid activity and to understand their relation to large-scale tectonics and magmatism. While the fluorites are of Early Jurassic to Oligocene age, carbonate (calcite, dolomite, siderite) and hematite dated by U-Pb small-scale isochrons records formation from Permian to Quaternary with a clear culmination in the Neogene.
These new age-data in combination with microthermometry data of primary fluid inclusions from growth zones in the fluorites and carbonates are used to constrain the timing of fluid signatures. This contribution shows that the ages are correlated with changes in fluid properties and/or tectonic events in the evolving continental crust. Comparison with published thermochronological data, apparent ages of URG-related volcanic rocks and the tectono-sedimentary evolution of the Upper Rhinegraben rift show clear correlations between the intensity of hydrothermal mineralization (and, hence, the intensity of fracture-bound fluid flow) with the U-Pb carbonate ages. This method accordingly provides an excellent tool to date rift-related processes like fluid flow, ore deposition and tectonic activation or reactivation of fractures.
Fluid properties changed after the deposition of Middle Triassic Muschelkalk evaporites from low salinity, high temperature (1–6 wt.% NaCleq, 200–270 °C, cooling late-metamorphic basement fluids) to high salinity, moderate temperature (20–26 wt.% (NaCl + CaCl2), 50–170 °C, mixture of a modified bittern brine (“basement brine”) with halite dissolution brine). This change led to large scale ore deposition (fluorite-barite-quartz with Pb-Zn-Cu, Bi-Co-Ni-Ag-U, Fe-Mn ores). During the Paleogene and Neogene, previously separated aquifers from various sedimentary units were connected by juxtaposition of the fluid source rocks during Rhinegraben rifting, which resulted in variable salinity and temperature fluids (1–26 wt. % (NaCl + CaCl2), 50–350 °C) by a multi-component fluid mixing process. Typical mineralization related to this shows barren or Pb-Zn-Cu veins with large amounts of barite.
A silicic ignimbrite flare-up episode occurred in the Pannonian Basin during the Miocene, coeval with the syn-extensional period in the region. It produced important correlation horizons in the ...regional stratigraphy; however, they lacked precise and accurate geochronology. Here, we used U–Pb (LA-ICP-MS and ID-TIMS) and (U–Th)/He dating of zircons to determine the eruption ages of the youngest stage of this volcanic activity and constrain the longevity of the magma storage in crustal reservoirs. Reliability of the U–Pb data is supported by (U–Th)/He zircon dating and magnetostratigraphic constraints. We distinguish four eruptive phases from 15.9 ± 0.3 to 14.1 ± 0.3 Ma, each of which possibly includes multiple eruptive events. Among these, at least two large volume eruptions (>10 km
3
) occurred at 14.8 ± 0.3 Ma (Demjén ignimbrite) and 14.1 ± 0.3 Ma (Harsány ignimbrite). The in situ U–Pb zircon dating shows wide age ranges (up to 700 kyr) in most of the crystal-poor pyroclastic units, containing few to no xenocrysts, which implies efficient recycling of antecrysts. We propose that long-lived silicic magma reservoirs, mostly kept as high-crystallinity mushes, have existed in the Pannonian Basin during the 16–14 Ma period. Small but significant differences in zircon, bulk rock and glass shard composition among units suggest the presence of spatially separated reservoirs, sometimes existing contemporaneously. Our results also better constrain the time frame of the main tectonic events that occurred in the Northern Pannonian Basin: We refined the upper temporal boundary (15 Ma) of the youngest counterclockwise block rotation and the beginning of a new deformation phase, which structurally characterized the onset of the youngest volcanic and sedimentary phase.
Paleogene karst bauxites in the northeastern Transdanubian Range and their cover sequences provide valuable sedimentary archives, despite their weathered nature and vague paleontological records. ...U–Pb detrital zircon geochronology combined with heavy mineral analysis indicates ‘local’ Alpine aeolian and fluvial sources and ‘distant’ aeolian sources connected to the Bohemian Massif. Records of episodic Paleogene volcanic eruptions related to igneous complexes of the Adamello and probably also the Bergell, Recsk and Balkan Peninsula, are reflected by euhedral zircon crystals. Their U–Pb geochronology supplies age constraints for the phases of subaerial exposure of the karstic surface and the accumulation of bauxitic protoliths and helps to improve the existing stratigraphic records and to define stages of denudation in the northeastern Transdanubian Range. Distinct phases of subaerial exposure and accumulation of the bauxite's protoliths are identified as ca. 42, 35 and 31 Ma; alternating with episodes of subsidence, represented by siliciclastic and carbonatic sequences at ca. 38, 32 and 31 Ma. Besides Paleogene volcanism, zircon dating also revealed contributions from the Middle Triassic tuffs of the Transdanubian Range. Garnet, epidote, kyanite, staurolite, and xenotime/monazite crystals suggest fluvial drainage of diverse metamorphic units of the Austroalpine basement from the Eastern- and Southern Alps, which also supplied most of the pre-Mesozoic zircons. However, the unexpectedly high proportion of Variscan ages in the bauxites most likely relate to igneous rocks of the Bohemian Massif, thus suggesting additional long-distance aeolian sources. The new data allow for detailed reconstructions of the Paleogene evolution and palaeogeography of the northeastern Transdanubian range.
Formation and evolution of the Pannonian Basin as part of the Mediterranean region was accompanied by eruptions of compositionally diverse magmas during the Neogene to Quaternary. The long-lasting ...magmatic activity began with some of the most voluminous silicic eruptions in Europe for the last 20 Myr. This paper describes the eruption chronology of this volcanic activity using new, high-quality zircon U-Pb dates, and provides the first estimates on the volume and areal distribution of the volcanic products, characterizes the magma composition and discusses the silicic magmatism in a region, where the continental lithosphere underwent significant extension. A thorough zircon geochronological study was conducted on samples collected from ignimbrites and pyroclastic fall deposits exposed in the Bükkalja Volcanic Field. In-situ LA-ICP-MS analysis on zircon grains provided a fast, cheap and accurate method for such detailed geochronological work, where the volcanic products occur in scattered outcrops that often have poor stratigraphic constraints. The interpreted eruption ages were determined from the youngest zircon age population within the samples and this methodology was validated by new single zircon CA-ID-TIMS dates and sanidine Ar-Ar ages. The volcanism covers about 4 Myrs, from 18.2 Ma to 14.4 Ma and involved at least eight eruptive phases. Within this, four large eruption events were recognized at 14.358 ± 0.015 Ma (Harsány ignimbrite), 14.880 ± 0.014 Ma (Demjén ignimbrite), 16.816 ± 0.059 Ma (Bogács unit) and 17.055 ± 0.024 Ma (Mangó ignimbrite), which are found in areas across the Pannonian Basin and elsewhere in central Europe. Considering all the potential sources of silicic ash found in the Paratethys sub-basins around the Pannonian Basin and along the northern Alps and in central Italy, we suggest that they were probably derived almost exclusively from the Pannonian Basin as shown by zircon U-Pb dates presented in this paper and published comparable age data from several localities. The new eruption ages considerably refine the Early to Mid-Miocene chronostratigraphy of the Pannonian basin, where the extensive volcanoclastic horizons are used as important marker layers.
The cumulative volume of the volcanic material formed during this 4 Myr long silicic volcanism is estimated to be >4000 km3, consistent with a significant ignimbrite flare-up event. Zircon crystallization ages indicate magma intrusions and formations of magma reservoirs in the continental crust for prolonged period, likely >1 Myr prior to the onset of the silicic volcanism accompanied with sporadic andesitic to dacitic volcanic activities. Mafic magmas were formed by melting of the thinned lithospheric mantle metasomatized previously by subduction-related fluids and emplaced at the crust-mantle boundary. They evolved further by assimilation and fractional crystallization to generate silicic magmas, which ascended into the pre-warmed upper crust and formed extended magma storage regions. Zircon Hf isotope and bulk rock Sr-Nd isotopic data indicate a sharp decrease of crustal and/or increase of asthenospheric mantle input after 16.2 Ma, suggesting that by this time the crust, and the lithospheric mantle was considerably thinned. This magmatism appears to have had a structural relationship to tectonic movements characterized by strike-slip and normal faults within the Mid-Hungarian Shear Zone as well as vertical axis block rotations, when the two microplates were juxtaposed. Our new zircon ages helped to refine the age of two major block-rotation phases associated with faulting. This volcanism shows many similarities with other rift-related silicic volcanic activities such as the Taupo Volcanic Zone (New Zealand) and the Basin and Range Province (USA).
•Summary of the massive Miocene silicic volcanism in the Pannonian Basin resulting >4000 km3 tephras•Eruption chronology of the volcanism based on >1400 U-Pb zircon dates from 19 samples.•Distal tephras in Paratethys sub-basins are correlated with three of the largest eruptive phases of the Pannonian Basin.•Recognition of the largest volcanic eruption episode in Europe for the last 20 Myr•The 18.2 to 14.4 Ma volcanism was coeval with continental rifting of the Pannonian Basin.
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•Integrated provenance analysis for reconstructing the Cretaceous source to sink system in NE China.•Permo-Carboniferous granitoids belong to the Jura-Triassic igneous units.•A large ...Cretaceous proto-basin proposed covering most of NE China.•The roll-back, and two-stage flat slab subduction of the Paleo-Pacific plate dominated the Cretaceous basin-and-range system.
The Cretaceous sedimentary successions in NE China are largely incomplete as the basins are inverted and younger strata are eroded. Except for the Songliao Basin, whose depositional record has remained relatively intact, the burial record to the east was interrupted in the late Early or Late Cretaceous. There is still controversy on the possible connection between the Songliao Basin and the eastern basin group, as well as the extent of the previously suggested “pan-Sanjiang” proto-basin that covered most current eastern satellite basins. To address these questions, we studied modern river catchments of variable sizes from sediment-supplying basement highs that cover most of eastern NE China to track the intense denudation events and provenance changes through the Cretaceous. We found a great inconsistency between detrital age patterns of the modern river sands and the spatial proportions of the source units. The detrital age distributions allow to re-evaluate the basement units that are mostly composed of the Triassic–Jurassic igneous suite and some metasedimentary units with Paleozoic ages, but the contribution from Proterozoic formations is negligible. Combining the newly dated modern catchment detrital U-Pb ages, the region-wide compilation of the basement emplacement ages, and the U-Pb ages in the Cretaceous formations in NE China, we systematically refine the Cretaceous provenance history. In the Early Cretaceous, the eastern satellite basins accumulated sediments from the Lesser Xing’an range (LXR) in the west, Zhangguangcai range (ZGCR) in the south, and the Nadanhada terrane (NT) in the east. The sediment of the southern Songliao Basin derived from the North China Craton (NCC) and from ZGCR but barely from the Great Xing’an Range (GXR). The Jiamusi uplift (JU) did not provide sediments to the eastern satellite basins and the Songliao Basin.
In the Late Cretaceous, the eastern satellite basins received sediments from the exhumed JU but barely from ZGCR and LXR. The Songliao Basin still accumulated the sediments from the NCC, some south part of ZGCR, and GXR but minor from the central and northern ZGCR and LXR. Between the latest Early Cretaceous and early Late Cretaceous, a much wider proto-basin was suggested in NE China than previously assumed. It covered during its maximum extension period the current Songliao Basin, the eastern satellite basins, the LXR, ZGCR, JU, and partial GXR basement areas. The provenance change is induced by the Paleo-Pacific plate motion change, i.e., with the subduction direction change, the roll-back, and two-stage limited flat slab subduction trigged the formation of the basin-and-range system in NE China since the Early Cretaceous. Moreover, we suggest conducting modern sand provenance analysis to detect, verify or re-classify the ages of the zircon-bearing units, especially at a reconnaissance prospecting on areas covered by imprecise large-scale geological maps only to reveal the catchment better.
Ciomadul is the youngest volcanic system in the Carpathian-Pannonian Region recording eruptive activity from ca. 1 Ma to 30 ka. Based on combined zircon U-Th and (U-Th)/He geochronology, Ciomadul ...volcanism is divided into two main eruptive periods: Old Ciomadul (1 Ma – 300 ka; OCEP) and Young Ciomadul Eruptive Period (160–30 ka; YCEP). OCEP activity comprises Eruptive Epochs 1–3, whereas new ages for eight lava domes and four pyroclastic units belonging to the YCEP lead to its further subdivision into two eruptive epochs: Eruptive Epochs 4 and 5. The extrusion of most of the lava domes occurred between 160 and 90 ka (Eruptive Epoch 4) during three eruptive episodes at ca. 155 ka, 135 ka and 95 ka (Eruptive Episodes 4/1, 4/2 and 4/3, respectively) along a NE-SW lineament, which is perpendicular to the regional NW-SE trend of the Călimani-Gurghiu-Harghita volcanic chain. Eruptive Epoch 5 occurred after a ca. 40 kyr of quiescence at ca. 55–30 ka, and is mainly characterized by explosive eruptions with a minor lava dome building activity. All of the dated pyroclastic outcrops, together with the lava dome of Piscul Pietros, belong to the older Eruptive Episode 5/1, with an eruption age of 55–45 ka. The eruption centers of Eruptive Epoch 5 are located at the junction of the conjugated NW-SE and NE-SW lineaments defined by the older eruptive centers. The whole-rock geochemistry of all studied samples is fairly homogeneous (SiO2 = 63–69 wt%, K2O = 3–4 wt%). It also overlaps with the composition of the lava domes of the Old Ciomadul Eruptive Period, implying a monotonous geochemical characteristic for the past 1 Myr. The eruption rates for the Ciomadul volcanism were determined based on the erupted lava dome volume calculations, supplemented with the eruption ages. The activity peaked during the Eruptive Epoch 4 (160–90 ka), having an eruption rate of 0.1 km3/kyr. In comparison, these values are 0.05 km3/kyr for the YCEP (160–30 ka) and 0.01 km3/kyr for the overall Ciomadul volcanism (1 Ma–30 ka). Based on the geochemical characteristics, the quiescence periods and the lifetime of the complex, as well as the relatively small amount of erupted material, this volcanic system can be placed in a subduction-related post-collisional geodynamic setting, which shows strong chemical similarities to continental arc volcanism. The commonly found long repose times between the active phases suggest that the nature of a volcano cannot be understood solely based on the elapsed time since the last eruption. Instead, comprehensive geochronology, coupled with the understanding of the magma storage behavior could be a base of hazard assessment for volcanic fields, where the last eruptions occurred several 10's of thousand years ago and therefore they are not considered as potentially active.
•Combined zircon U-Th and (U-Th)/He geochronology for eruption dating•A volcanic activity unit-based conceptual model for the youngest volcanism in the Carpathian-Pannonian Region•The role of the long repose times to understand the nature of a volcanic field•Eruption behavior of a post-collisional volcano with monotonous geochemistry
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