Zircon Geochronology Research Articles

Age, petrogenesis, and metamorphic modelling of high‐pressure garnet‐amphibolite from the Tethyan Himalayan Sequence of Bhagirathi Valley, Western Garhwal Himalaya

The Cenozoic Himalayan Orogeny is a manifestation of subduction and subsequent collision of the Indian lithosphere with the Asian Plate in the Eocene, resulting in the formation of intra‐terrane shear zones and regional metamorphic belt along the strike of the entire orogen. This metamorphic belt contains high‐pressure (HP) metamorphic rocks (garnet‐amphibolite, late‐stage granulite, and host gneisses) at various structural levels in the Himalayas. In the present study, we carried out geochemical, chronological, and metamorphic modelling of an exotic tschermakite‐bearing garnet‐amphibolite unit exposed within the Tethyan Himalayan Sequence of Western Garhwal Himalaya of India. Bulk‐rock geochemistry suggests the protolith's tholeiitic fractionation trend and trachy‐andesitic nature. U–Pb geochronology of zircon reveals an age spectrum with pronounced clusters at ~1,550 Ma, ~1,350 Ma, 1,100–1,150 Ma, 900–930 Ma, and ~550 Ma. There is a possibility that the protolith of the HP garnet amphibolite is magmatic. However, near‐concordant ages at certain intervals might suggest crustal components from multiple sources. Integrated geothermobarometry and P–T pseudosection modelling indicate high‐P/medium‐T conditions (~1.65 GPa and 650°C) of peak metamorphism. Based on these results, we infer that this garnet‐amphibolite represents pre‐Himalayan Indian lower crust and during India–Asia collision. The leading edge of the Indian continental lithosphere subducted where mafic and some of the felsic lithologies underwent HP garnet‐amphibolite facies metamorphism, and after a possible slab break‐off, these rocks exhumed during the Himalayan orogeny.

Metallogenesis of the Bakoshi-Kundila gold deposit in northern West Nigerian Subshield: Insights from pyrite chemical and sulfur isotopic compositions and zircon U-Pb geochronology

The Bakoshi-Kundila gold deposit, located in northern West Nigerian Subshield, in the southern trans-Saharan Orogenic Belt of West Africa, is a recent discovery and artisanally mined deposit. Like other Nigerian gold deposits, the mechanism and timing of gold precipitation remains unknown. In this study, we report the results of an integrated study of pyrite chemical and isotopic compositions and U-Pb on zircon geochronology to determine the gold precipitation mechanisms, fluid sources, and formation age of the gold mineralization. Two mineralization stages are recognized: (i) the Au-pyrite-quartz vein-type mineralization, including two generations of pyrite referred to as Py1a and Py1b, and (ii) wall rock disseminated-type Au-pyrite mineralization, comprising three pyrite types, Py2a, Py2b, and Py3. Py1 is Au-rich and As-poor pyrite and contain lattice-bound Au (Au+), nanoparticle Au (Au0), and native Au grains adsorbed on Py1b surface. Associated with Py1 are Ag-Te-Au bearing minerals. In contrast, Py2 and Py3 are As-rich and are less in Au; they contain only lattice-bound Au. Py1 grains have higher contents of Ag, Pb, Bi, Sb, Tl, and Cu which correlate with Au compared to those from Py2 and Py3. Py1 generations has lower δ34SV-CDT from –5.43 to –2.11 ‰ compared to the higher values of +3.63 to +5.47 ‰ obtained for the Py2 and Py3. These sulfur isotopes data are within the δ34S values of 0 ± 5 ‰ of the magmatic reservoir. U-Pb on zircon from Au-pyrite-quartz vein stage yielded older ages of 644.5 ± 2.2 Ma and 681.5 ± 1.8 Ma, compared to younger age of 606. 4 ± 1.8 Ma yielded by zircon grains from wall rock-type mineralization. Additionally, zircon grains from Au-bearing Tourmalinite yielded ages of 679 ± 1.3 Ma and 609.6 ± 7.1 Ma. We propose that Au mineralization at the Bakoshi-Kundila occurred during two periods in the Neoproterozoic: (i) an early ∼ 682 Ma (Cryogenian), possibly related to the emplacement of 683 Ma Yettiti granite and (ii) a second-stage Au disseminated in wall rock of granites and might have experienced 606–610 Ma Ediacaran metamorphism during the late tectonic events in West Nigerian Subshield.

Geological framework of the concealed East Tennant area constrained by SHRIMP U–Pb zircon geochronology: Implications for Paleoproterozoic stratigraphic correlations in northern Australia

The fundamental geological framework of the concealed Paleoproterozoic East Tennant area of northern Australia is very poorly understood, despite its relatively thin veneer of Phanerozoic cover and its position along-strike from significant Au–Cu–Bi mineralisation of the Tennant Creek mining district within the outcropping Warramunga Province. We present 18 new U–Pb dates, obtained via Sensitive High Resolution Ion Micro Probe (SHRIMP), constraining the geological evolution of predominantly Paleoproterozoic metasedimentary and igneous rocks intersected by 10 stratigraphic holes drilled in the East Tennant area. The oldest rocks identified in the East Tennant area are two metasedimentary units with maximum depositional ages of ca. 1970 Ma and ca. 1895 Ma respectively, plus ca. 1870 Ma metagranitic gneiss. These units, which are unknown in the nearby Murphy Province and outcropping Warramunga Province, underlie widespread metasedimentary rocks of the Alroy Formation, which yield maximum depositional ages of 1873–1864 Ma. While parts of this unit appear to be correlative with the ca. 1860 Ma Warramunga Formation of the Warramunga Province, our data suggest that the bulk of the Alroy Formation in the East Tennant area is slightly older, reflecting widespread sedimentation at ca. 1870 Ma. Throughout the East Tennant area, the Alroy Formation was intruded by voluminous 1854–1845 Ma granites, contemporaneous with similar felsic magmatism in the outcropping Warramunga Province (Tennant Creek Supersuite) and Murphy Province (Nicholson Granite Complex). In contrast with the outcropping Warramunga Province, supracrustal rocks equivalent to the 1845–1810 Ma Ooradidgee Group are rare in the East Tennant area. Detrital zircon data from younger sedimentary successions corroborate seismic evidence that at least some of the thick sedimentary sequences intersected along the southern margin of the recently defined Brunette Downs rift corridor are possible age equivalents of the ca. 1670–1600 Ma Isa Superbasin. Our new results strengthen ca. 1870–1860 Ma stratigraphic and ca. 1850 Ma tectono-magmatic affinities between the East Tennant area, the Murphy Province, and the mineralised Warramunga Province around Tennant Creek, with important implications for mineral prospectivity of the East Tennant area.

Late Paleozoic cratonal sink: Distally sourced sediment filled the Anadarko Basin (USA) from multiple source regions

AbstractThe Anadarko Basin (south-central USA) is the deepest basin on the North American craton and occupies a region largely surrounded by major, late Paleo-zoic plate-margin (Marathon-Ouachita-Appalachian) and intraplate (Ancestral Rocky Mountains) orogenic systems, albeit a distal arm of the latter. The Anadarko Basin hosts an exceptionally voluminous record of Pennsylvanian strata, and much of this fill has been attributed to erosion of the adjacent Wichita uplift—composed of granitic and rhyolitic rocks of Cambrian age—separated from the basin by a fault zone exhibiting 12 km of vertical separation. This work incorporates thin-section petrography (102 samples) and U-Pb detrital zircon geochronology of sandstone samples (12 samples) from core and outcrop of the Middle Pennsylvanian Red Fork Sandstone (and equivalents) as well as slightly younger Upper Pennsylvanian units (Tonkawa, Chelsea, and Gypsy sandstones) in order to interpret drainage pathways and evolution of those pathways toward and into the Anadarko Basin (Oklahoma) and evaluate the relative importance of the major provenance regions.Our petrographic analysis indicates sandstones with arkosic compositions are limited to the region immediately adjacent to (north of) the Wichita uplift. All remaining samples, which reflect the vast bulk of sediment in the depocenter, including sediment on the northern and eastern Anadarko shelf, are litharenites. Analysis of kernel density plots of the U-Pb ages of detrital zircons together with multidimensional scaling analysis of the Middle Pennsylvanian samples indicate three groups of similar provenance: (1) samples dominated by Cambrian ages from locations directly adjacent to the Wichita uplift; (2) samples dominated by Neoproterozoic ages from locations along the northern shelf of the Anadarko Basin; and (3) samples dominated by Mesoproterozoic ages from locations along the eastern Anadarko shelf and the basin center. These samples are spatially discrete, indicating partitioning of drainage networks during the Middle Pennsylvanian, with two continental-scale fluvial systems entering the Anadarko Basin from the north (transversely) and east (axially). The lack of Cambrian ages in the depocenter and (northern) shelf samples indicate that the Wichita uplift supplied only limited sediment to the basin; sediment derived from the uplift was trapped in fringing fans directly adjacent to the uplift. In contrast to the patterns exhibited by the Middle Pennsylvanian samples, Upper Pennsylvanian samples exhibit more uniform U-Pb ages across the basin. This indicates the relatively rapid evolution of the Appalachian-derived northerly and easterly drainages into an integrated system that flowed axially across the (overfilled) mid-continent basins to the ultimate continental sink in the Anadarko Basin.

Early Cambrian S-type granites in the Sakarya Zone, NE Turkey: A record for transition from subduction to post-collisional extension deduced from U Pb zircon age and Nd Hf isotopes

Cadomian realms have recently received much attention in the Alpine–Mediterranean orogenic belts, with discontinuous outcrops extending from the Alps to the İstanbul Zone, Menderes Massif, Taurides in Turkey and Iran as well. However, they have not been identified in the Sakarya Zone, northern Turkey to date. Here, we present, for the first time, zircon UPb geochronology, zircon Hf-isotopes and trace elements as well as whole-rock geochemistry and Nd-isotopes from the Karameşe metagranitoid in the Yusufeli (Artvin) area, NE Turkey. The zircon UPb age data demonstrate that the Karameşe metagranitoid intruded into the Precambrian basement units in the Early Cambrian (ca. 534–530 Ma). Zircon overgrowths in the Karameşe metagranitoid interpreted as a result of metamorphic overprint yielded ages of 328 Ma. This age indicates that the Sakarya Zone experienced the Variscan metamorphic events at 328 Ma. The Early Cambrian metagranitoid shows that some rocks in the basement of the Sakarya Zone date back to Precambrian in age. The Karameşe metagranitoid is an S-type granite, with high modal content of muscovite (~10%). The samples show highly peraluminous [A/CNK = molar Al2O3/(CaO + K2O + Na2O) = 1.34–1.58] and medium-K calc-alkaline geochemical affinities. The Karameşe metagranitoid displays low REE concentrations and a slight positive Eu anomaly and show slightly light REEs and LILEs enrichments, and HFSEs depletions. The samples have negative εNd(t) of −4.76 to −2.90 and εHf (t) of −4.75 to −1.08 values. These geochemical-isotopic characteristics reveal that the Karamaşe metagranitoid originated through fluid-absent muscovite dehydration melting of heterogeneous metasedimentary source rocks (mostly greywacke), with a minor input of juvenile mafic melt. We argue that the Early Paleozoic metagranitoids along the eastern Sakarya Zone is an expression of crustal thinning in the Cadomian orogenic belt in northern Gondwana, with the tectonic turnover from convergent margin to crustal extension possibly induced by break-off of Tornquist oceanic lithosphere which is a branch of Iapetus Ocean during Early Cambrian.

Multiple episodes of early Precambrian magmatism and tectonism in the Tarim Craton: A North China connection

The accretion and recycling of Archean-Paleoproterozoic continental crust is the key to understanding the formation and evolution of early continental crust. Early Precambrian metamorphic basement is well developed in the Aktashtagh area, southeastern margin of the Tarim Craton, northwestern China. We report zircon SHRIMP UPb dating, LA-MC-ICP-MS LuHf isotopic analysis and whole-rock geochemical analysis on 16 samples (mainly TTG, tonalite-trondhjemite-granodiorite) from Aktashtagh. Multiple episodes of early Precambrain magmatism, including 3.72 Ga, 3.63 Ga, 3.10 Ga, 2.83–2.69 Ga, 2.55–2.50 Ga, 2.05–2.02 Ga and 1.93–1.82 Ga events, have been identified in the Aktashtagh region. The most intense magmatism occurred in the late Mesoarchean to early Neoarchean. Significantly, 3.63 Ga and 3.10 Ga TTG rocks are identified, together with more extensive 2.8–2.7 Ga and ∼ 2.5 Ga TTG rocks. The TTG suites are dominated by tonalitic, with some trondhjemitic and grandioritic rocks. They show large variations in REE contents, are mainly distributed in the high- and medium-pressure fields in the Sr/Y-Y and La/Yb-Yb diagrams, and the 2.7 Ga TTG rocks commonly show higher and more variable Sr/Y and La/Yb ratios. The 3.63–3.10 Ga TTG rocks have magmatic zircon εHf(t) values of −3.9 to +3.1 and tDM1(Hf) model ages of 3.9–3.6 Ga, whereas the ∼2.7–2.51 Ga TTG rocks have magmatic zircon εHf(t) values of −13.4 to +2.1 and tDM1(Hf) model ages of 3.3–3.0 Ga. The ∼2.7 to ∼2.0 Ga meta-gabbroic-dioritic rocks have magmatic zircon εHf(t) values of −19.7 to +0.6 and tDM1(Hf) model ages of 3.2–2.4 Ga. Metamorphic zircon ages of 3.56 Ga, 2.75–2.73 Ga, 2.53–2.51 Ga, 2.03–1.96 Ga and ∼ 1.85 Ga are also recorded, whereas ∼2.83 Ga, 2.53–2.40 Ga, 2.05–2.02 Ga and 1.86–1.83 Ga crustally-derived K-rich granites are identified, with the most important occurring in the late Neoarchean and late Paleoproterozoic. In this regard, the Tarim Craton is similar to the North China Craton in its early Precambrian geological evolution. The main difference is that the Paleoproterozoic tectonothermal event in the Tarim Craton started as early as 2.00 Ga, whereas in the North China Craton it occurred between 1.95 and 1.80 Ga.

Provenance of sediments in the northern Manila Trench: An assessment from detrital zircon geochronology

Provenance of sediments in the northern Manila Trench: An assessment from detrital zircon geochronology

Origins of clay-rich strata in Cenozoic paleochannel deposits: an example from Suttor Formation, Queensland

Cenozoic sediments cover much of Queensland’s landscape and record changes in climate and flora that evolved in tandem with the tectonic evolution in eastern Australia, associated with uplift and erosion events arising from Late Cretaceous sea-floor spreading in the Coral Sea, leading to the passive margin we see today. In eastern Australia, incised and potentially fault-bounded valleys developed on the pre-Cenozoic landscape and were variably infilled at different times by siliciclastic sediments, carbonaceous muds and peat, and basaltic lava flows. This study examines a 100 m-deep drill core through one such siliciclastic-dominated paleochannel incised into upper Permian coal measures on the western limb of the Bowen Basin. Palynological analysis, core logging, hyperspectral logging of the core, X-ray diffraction (XRD), SEM–EDS and U–Pb zircon geochronology were used to investigate the age and origins of these clay-rich deposits. Palynological analysis confirmed that the strata belong to the upper Paleogene and Neogene Suttor Formation, a time when Australia’s climate has been interpreted to shift from wet and warm to a more arid setting. Core logging revealed that the sequence in the studied channel began as a breccia/alluvial fan with chaotic angular clasts of Permian laminated siltstone, tuff and coal floating in disturbed poorly lithified sand with evidence of soft sediment deformation, possibly initiated by localised faulting. These clasts were continually reworked and broken down into a clast supported pebble conglomerate capped by a series of claystone with intermittent carbonaceous claystone and lignite, interpreted to have formed in a lacustrine environment that could be localised on the floodplain (oxbow) or more regional in extent. Above this, and interpreted from palynology as corresponding to a climatic shift to more arid conditions, are well sorted but subrounded sugar sands and intermittent clays with abundant iron staining (?paleosols) interpreted to represent sandy ephemeral channels. These are overlain by extremely weathered undated basalts. The hyperspectral logging of the core and XRD studies of the white claystone samples indicate that they are kaolinite-rich, but observations under SEM–EDS noted that their honeycomb structure mimicked that of smectite. The presence of abundant zircon suggested the possibility of syndepositional volcaniclastics, but U–Pb zircon geochronology recorded an age of 272–254 Ma (middle to late Permian). Hence local recycling of the tuffaceous smectite-rich coal measures within the incised alluvial system, assisted by intense weathering under a warm and wet climate, and potentially acid leaching from the organic-rich layers was the origin of the kaolinite-rich clay strata. KEY POINTS Clay-rich Cenozoic paleochannels in the northern Bowen Basin belong to the upper Paleogene and Neogene Suttor Formation, based on palynological study. The clay-rich strata are developed by local recycling of middle to late Permian tuffaceous smectite-rich coal measures. The interpretation based on palynology and clay mineralogy confirm that Australia experienced a shift from wet and warm to a more arid climate during the upper Paleogene and Neogene.

Paleoproterozoic (ca. 2.1–1.9 Ga) dioritic-granitic magmatism in the Dunhuang Terrane, Northwestern China: Implications for petrogenesis and tectonic evolution

The implications of petrogenesis and tectonics of Paleoproterozoic (ca. 2.1–1.9 Ga) granitoid rocks in Dunhuang Terrane have hitherto received less attention. According to data from zircon UPb dating, the ages of dioritic gneiss, granodioritic gneiss and potassic granite are 2045 ± 44 Ma, 1998 ± 15 Ma and 1950 ± 38 Ma, respectively. The dioritic gneiss has MgO = 1.87–2.93 wt% (Mg# = 46.8–50.9), Yb ≤ 1.9 ppm and Y ≤ 18 ppm, with variable εHf(t) (−2.8 − +5.5) and εNd(t) (−5.6 − +1.3) values, indicating that the mantle wedge source above the subducted slab contributed with subduction fluids and ocean sediment melt in an arc setting. The granodioritic gneiss has relatively high MgO (3.00–1.83 wt%), variable Cr (13.5–106 ppm) and Ni (12.2–72.9 ppm), negative εHf(t) (−20.4 to −10.1) and εNd(t) (−15.2 to −12.8) values, and high P2O5 and TiO2 saturation temperatures (∼800 °C). These data indicate magma source of late Paleo- to early Mesoarchean (∼3.2–3.1 Ga) continental crust rocks. The potassic granite has high K2O (5.52–6.79 wt%) and low MgO (0.10–0.19 wt%) concentrations, low Mg# (37.7–44.6) values, and negative εHf(t) (−12.8 to −2.5) and εNd(t) (−10.6 to −4.8) values. These results suggest that pre-existing Neoarchean crustal rocks were partially melted possibly under transitional stage from syn- to post-collision. Compared with the adjacent areas, Paleoproterozoic (ca. 2.1–1.8 Ga) evolutionary period related to assembly of Columbia supercontinent in Dunhuang Terrane is comparable with that in northeastern Tarim Craton and southwestern Alxa Block, but terminated ∼100 Ma later than that in southeastern Tarim Craton (Aketashtage Terrane).

Decoding post‐orogenic sediment recycling and dispersal using detrital zircon core and rim ages

AbstractDetrital zircon (DZ) geochronology has become a popular tool in provenance studies during the past two decades. However, similar zircon crystallization ages from different source regions greatly hamper the interpretation of sediment dispersal and recycling processes. The Alleghenian–Ouachita–Marathon (AOM) foreland and vicinity in North America is a region where some dominant DZ age groups could come from both the southern Appalachians in the eastern United States and the Gondwanan terranes in Mexico. In this study, we present 1045 new DZ U–Pb ages and 81 DZ core–rim age pairs in lower Permian sandstone in the Permian Basin and Miocene sandstone in the eastern Gulf of Mexico (GOM). These new data were integrated with published DZ single U–Pb age and core–rim ages from syn‐ to post‐orogenic strata in the Permian Basin, Marathon foldbelt, southern Appalachian foreland basin and eastern GOM to interpret the sediment‐dispersal models in the AOM foreland and eastern GOM. Our models show that during the Leonardian Stage, sediments derived from the Appalachians were first delivered to the US midcontinent and then recycled to the Permian Basin; during the Miocene, sediment from the Appalachians fluxed to the eastern GOM, with no longshore mixing from the western GOM. These models based on the integration of single U–Pb and core–rim ages are consistent with published results that used other methods, including zircon single U–Pb age, zircon Hf isotopic data, zircon (U–Th)/He age, sedimentology and stratigraphy. Our results demonstrate that although some limitations exist, zircon core–rim age is a powerful tool, adding an extra constraint on the interpretation of sediment‐dispersal systems. This tool is particularly applicable to the post‐orogenic stage, during which the sediment pathways are more complicated because of the dominant input from distal sources. Insights gained in this study imply that this novel strategy of using core and rim ages could be integrated with other methods to better understand sediment dispersal.

‘I hate sand … it gets everywhere’—Phanerozoic sedimentary recycling from NW Africa

AbstractOver 10,000 published detrital zircon ages have been reprocessed (applying a +10% normal and reverse concordance range) and analysed to understand the evolution of the detrital zircon record of north‐west Africa during the Phanerozoic. Using dissimilarity and clustering analysis, shifts in detrital zircon populations allow interpretation of the evolution of source regions and source to sink systems throughout the Phanerozoic within the West Gondwana superfan. Previous thermochronology and field studies conducted across north‐west Africa indicate significant and sustained shifts in source regions in Meso‐Cenozoic times which are not recorded in the detrital zircon geochronology record. This discrepancy is most notable for Mesozoic to modern source to sink studies focused on the evolution of the Atlasic rift and opening of the Atlantic and Tethyan Oceans to the west and north respectively. Our results indicate a high degree of similarity between samples from Cambrian times onwards due to successive phases of sediment recycling. This highlights the need to integrate detrital zircon analysis with other techniques to provide confident reconstruction of sediment routing systems across Morocco. This systematic review also reveals the ubiquitous occurrence of Mesoproterozoic zircons within Moroccan sediment. No basement of this age is known from north‐west Africa—often described as the ‘Mesoproterozoic Gap’, which was thought to be a diagnostic feature of sediment derived from the West African Craton. However, zircons of this age form 7% of all analysed zircons and are present in sediments from at least 700 Ma. The presence of this population is interpreted as strongly diagnostic of provenance from either the Amazonian Craton or the Eastern Gondwana Orogen within Central Africa. Their presence in the Moroccan detrital record from the Neoproterozoic onwards raises questions about the position of the West African Craton in the Proterozoic, and for the spatial extent of Mesoproterozoic orogeny within north Africa.

An example of a Neoproterozoic hyperextended margin: An integrated perspective of the basic magmatism recorded in the Andrelândia Basin, central Ribeira Orogen, SE-Brazil

Deformed amphibolite to granulite-facies metasedimentary rocks of Andrelândia and Raposos Group, associated metabasic rocks witnessed the evolutionary stage of the Andrelândia sedimentary basin, within Central Ribeira orogen, bordering the southern São Francisco Craton. Despite detailed geological maps and provenance studies, there is still a knowledge gap and debate on the stratigraphic pile and the age of sedimentation in the Andrelândia basin. New data regarding metabasic rocks interlayered in Andrelândia basin is presented, including detailed geological mapping, lithogeochemistry, Sm-Nd and Rb-Sr isotopes and LA-ICPMS U-Pb zircon geochronology. The metabasic rocks occur as centimetric to metric lenses with sharp contacts with the metasedimentary country rocks, displaying the same ca. 620–580 Ma age span of metamorphism and deformation. Geochemical results indicate high-TiO2 within-plate to low-TiO2 MORB to E-MORB signatures for lower and upper units of the distal Raposos Group. Additionally, only low-titanium MORB-like metabasites were found in the most proximal unit, Andrelândia Group. One sample within the Raposos Group yielded crystallization age of ca. 653 Ma, metamorphic overprint at ca. 579 Ma and Paleo to Mesoproterozoic inherited zircon grains. The metabasic rocks interleaved in the Andrelândia Group, Nd TDM model ages are between 1.10 and 1.90 Ga, with εNd (653 Ma) varying between −8 to + 2.1 and 87Sr/86Sr (653 Ma) values between 0.7144 and 0.7033. Nd TDM model ages are between 1.80 and 2.0 Ga, with negative εNd (653) −14 to −0.2 and initial 87Sr/86Sr between 0.7157 and 0.7043. The results indicate an isotopic similarity with the biotite schists of the Santo Antônio Unit, previously considered as arc-derived in an active margin setting. Together with previously published isotopic and geochronology data, and with the structural distribution of the units and tectonic interleaved basement slices in the distal Raposos Group, we envisage a tectonic model with syn-to-late depositional basic magmatism between ca. 760 to 653 Ma. The proposed model compares the evolution of Andrelândia-Raposos basin with modern hyper-extended magma poor rifted continental margin sedimentary basins as plausible tectonic setting. Finally, the results are compared with those from the Araçuaí orogen, the Northern part of the Araçuaí-Ribeira Orogenic System, displaying similarities in ages and composition.

SHRIMP U-Pb zircon geochronology of the carbonatite-hosted REE deposit of Kamthai, Late Cretaceous polychronous Sarnu Dandali alkaline complex, NW India: Links to plume-related metallogeny and CO2 outgassing at the K-Pg boundary

The carbonatite plug at Kamthai in the Late Cretaceous polychronous (66–89 Ma) Sarnu- Dandali alkaline complex (SDAC), NW India, is India’s only known carbonatite-hosted rare- earth-element deposit. The SDAC intrudes the Neoproterozoic (∼750 Ma) Malani silicic igneous suite in the Aravalli raton. The Kamthai carbonatite is a calcio-carbonatite dominated by calcite along with barite, strontianite, quartz, zircon and REE-bearing minerals. Textural features suggest an open-system exchange of the magma chamber at varying depths of crystallization. REE patterns are smooth and characterized by strong LREE enrichment, as typical of carbonatites. SHRIMP dating of 12 spots on three magmatic zircons from the carbonatite yielded a concordia age of 66.1 ± 1.4 Ma and an indistinguishable average 206Pb/238U mean age of 68.4 ± 1.8 Ma. The obtained U-Pb ages unambiguously link the carbonatite emplacement to the Deccan Large Igneous Province, i.e. the Réunion hotspot near the K-Pg (Cretaceous-Paleogene) boundary in the polychronous set-up of the SDAC. These ages are also indistinguishable from the 68.53 ± 0.16 Ma magmatic pulse recorded from the nearby Mundwara polychronous alkaline complex and the 69.7 ± 0.2 Ma alkaline sills from the Tethyan suture zone in Pakistan, which are regarded to be earliest manifestations of the Réunion hotspot in the Indian sub-continent. Our results in the context of REE mineralization in the Kamthai deposit have also implications with respect to CO2 outgassing, induced by at least four near-synchronous carbonatitic eruptions in NW India, and to triggering the mass extinction near the K-Pg boundary.

Locating northern Qiangtang on the margin of Gondwana or Laurasia? Evidence from detrital zircon geochronology

• The Permian sandstones of the northern Qiangtang terrane are quite possibly sourced from Gondwana-affinity terranes, such as the southern Qiangtang and Lhasa terranes. • The northern and southern Qiangtang terranes were essentially a unified block during the Late Paleozoic. • The northern Qiangtang terrane was located on the northern margin of Gondwana during the Permian. The relationship between the northern Qiangtang terrane and other blocks in Gondwana and Laurasia continents is still controversial. Here we report U-Pb ages of detrital zircons from the Lower-Middle Permian Nuoribagaribao Formation in the northern Qiangtang terrane, which provides new evidence to constrain the tectonic affinity of the northern Qiangtang terrane during the Late Paleozoic. Sandstones from the middle and upper parts of the Nuoribagaribao Formation contain dominant Ordovician to Devonian (480–360 Ma, peaking at 368 Ma) and Late Paleoproterozoic to Early Mesoproterozoic (1800–1400 Ma, peaking at 1557 Ma) detrital zircons. The U-Pb age spectrum of detrital zircons of them is consistent with those of the Carboniferous strata in the southern Qiangtang and Lhasa terranes to the south; this indicates that rather than being sourced from the Yangtze Block to the east and the Eastern Kunlun-Qaidam-Qilian terrane to the north, the sediments of the Nuoribagaribao Formation were most probably sourced from the Carboniferous strata in the southern Qiangtang and Lhasa terranes to the south or shared the same sources as them. The high similarity of detrital zircon age patterns between the northern and southern Qiangtang terranes, together with other lines of geological evidence, such as paleomagnetism and paleontology, indicate that the northern and southern Qiangtang terranes were essentially a unified block during the Late Paleozoic and were located on the northern margin of Gondwana.

Late Paleozoic to early Mesozoic tectonic evolution of Japan based on crystal morphologies and U–Pb ages of detrital zircons from the middle Permian sedimentary succession, Maizuru Belt, Southwest Japan

• Detrital zircon geochronology for middle Permian sandstones in Maizuru Belt. • We determined the question of Permian collisional interpretation of Japan. • Collision of island arc and Sino-Korean Block happened at middle Permian. • Tectonic evolution accompanied by collision of island arc and Sino-Korean Block. The late Paleozoic to early Mesozoic collision-related orogeny in Japan needs to be studied to understand the tectonic evolution of Japan and East Asia. Morphological analysis and U–Pb ages of detrital zircons from sandstones of the middle Permian sedimentary succession (the Mushikawa Formation), Maizuru Belt, Southwest Japan, were used to constrain the timing of the tectonic evolution during the island arc collision and their provenance characteristics. Detrital zircon age ranges from the sandstones changed stratigraphically upward. Sandstones from the lower and upper successions contained zircon grains with main age clusters of ca. 300–260 Ma and multiple age clusters of ca. 2300–1800 and 500–270 Ma, respectively. The late Paleozoic zircons are mostly long and less rounded, while those of the Precambrian to middle Paleozoic zircons are mostly short and rounded. U–Pb ages and morphological features indicate that the late Paleozoic zircons were derived from a nearby region, whereas the pre-late Paleozoic zircons were supplied from distant sources and strong hydrodynamic conditions at the time of deposition. Combining the results of this study with the geological information of East Asia revealed that the sources changed from the Southern zone of the Maizuru Belt to multiple areas, such as the Southern and Northern zones of the Maizuru Belt, Oeyama Ophiolite, Sino–Korean Block, and Central Asian Orogenic Belt. Moreover, the results of this study support that the island arc and continental margin of the Sino–Korean Block collided during the middle Permian.

Origin, timing and paleogeographic implications of Paleogene karst bauxites in the northern Transdanubian range, Hungary

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.

Introduction pages, Nova Geodesia 2(3), 2022

Nova Geodesia (https://novageodesia.ro), Issue 3, Volume 2, 2022: The papers published in this issue represent interesting novelties in different topics of geodetic science. Among the exciting articles, we invite readers to find news about: Identification and evaluation of the risk induced by landslides based on G.I.S. models of spatial analysis, a case study: Bicazu Ardelean, Romania; Correlation between land surface temperature (LST) and normalized difference vegetation index (NDVI) in Wardha Valley Coalfield, Maharashtra, Central India; Tectonic evolution of the Qinling Orogenic Belt, Central China – new evidence from geochemical, zircon (U-pb) geochronology and HF isotopes.

Tectonic evolution of the Qinling Orogenic Belt, Central China – new evidence from geochemical, zircon (U-pb) geochronology and HF isotopes

The paper deals with a review of tectonic evolution in different regions of China with the help of different techniques and models. Tectonic evolution shows that in the shallow layers of China the structural impact is not solid, and huge structural zones are deficient within the list and incline zones where the principal wretchedness and delicate slant zones framed. The Qinling Orogenic Belt (QOB) situated between the North China Craton (NCC) and the Yangtze Craton (YZC) is made from the Northern Qinling Belt (NQB) and the Southern Qinling Belt (SQB). The Hf isotopic creations of zircons from the different rocks recommend that the NQB most likely created on the cellar of the southern NCC. The stones in the SQB show zircon age spectra and Hf-isotope structures like those in the northern YZC, recommending a nearby proclivity. We thusly decipher the SQB to have created on the cellar of the northern YZC. Incorporating the new information in this investigation with those from past works, we propose another structural model for the development and advancement of the QOB during late Mesoproterozoic to early Paleozoic including the accompanying significant occasions: (1) Late Mesoproterozoic to early Neoproterozoic (Grenvillian) toward the north subduction of the Songshugou Ocean; Early-center Neoproterozoic (870-800 Ma) bidirectional subduction and impact; Middle Neoproterozoic (∼800-710 Ma) post-crash expansion; Middle-late Neoproterozoic (710-600 Ma) inside plate augmentation; Late Neoproterozoic-early Paleozoic (600-520 Ma) opening of the Shangdan Ocean; and Early Paleozoic (520-420 Ma) subduction-crash. We accordingly follow in any event two unmistakable Wilson cycles in the QOB.

Mid−late Neoproterozoic tectonic evolution of the northern margin of the Yangtze Block, South China, as constrained from the detrital zircon record

The northern margin of the Yangtze Block (NYB) experienced distinct tectono-magmatic evolution during the mid- and late-Neoproterozoic, as compared with the northwestern margins of the Yangtze Block (NWYB), although the geodynamic mechanism remains controversial. The South Qinling Belt (SQB), which forms the northernmost NYB, is a significant target for studying the Neoproterozoic tectonic evolution of the NYB. Here we present U-Pb geochronology and Lu-Hf isotopes of detrital zircons from clastic rocks belonging to the Yaolinghe and Wudangshan Groups in the SQB. The U-Pb ages reveal that the maximum depositional ages are respectively ca. 630 Ma and ca. 680 Ma for the Yaolinghe and Wudangshan Groups in the Ankang and Wudang Uplifts. Based on the compilation of U-Pb ages and Hf−Nd−O isotopic data as well as multidimensional scaling (MDS) analysis, clastic rocks of the Yaolinghe Group are suggested to be sourced mainly from the NWYB, whereas those of the Wudangshan Group were derived mostly from the NWYB and the NYB. The data compiled also indicate ca. 800−680 Ma northeastward migration of magmatism in response to slab rollback and ca. 680−600 Ma eastward migration of magmatism resulting from slab tearing. A tectonic model is proposed that envisages an arcuate subduction system around the Yangtze Block during the mid−late Neoproterozoic. The continuous slab rollback and slab tearing underneath the NYB resulted in an extensional environment at that time. The rocks in the NWYB underwent uplift and erosion, and the detritus was transported to the NYB. The new model can well account for the two distinct groups of volcanic rocks in the Yaolinghe Group.

The Evolution of Permian Source-to-Sink Systems and Tectonics Implications in the NW Junggar Basin, China: Evidence from Detrital Zircon Geochronology

The basin type of the Junggar Basin changed during the Permian, but the time constraint of the tectonic evolution remains unclear. Besides, the fan deltas developed in the Permian in the Mahu Sag in the northwestern of the oil-rich basin. However, the provenances of the sedimentary systems remain unclear. Based on petrology and detrital zircon U-Pb ages, this study investigates the source-to-sink systems evolution and tectonics implications. Abundant lithic clasts in sandstones with low compositional and textural maturity imply proximal sources. The dating results showed a dominant peak (310–330 Ma) and a secondary peak (400–440 Ma) in the northern Mahu Sag, only one peak at 295–325 Ma in the central Mahu Sag, several peaks at 270–350 Ma in the southern Mahu Sag, and multiple peaks at 370–450 Ma in the Zhongguai Uplift. Thus, the north-western Junggar Basin was divided into four major source-to-sink systems, with adjacent central West Junggar as the main provenance and northern and southern West Junggar as the secondary provenance. The proportion of sediment supply from the southern and northern West Junggar is higher during the Middle-Late Permian. It suggests that the source-to-sink systems show inheritance and evolve from a single provenance into a complex provenance, indicating the uplift of West Junggar. The tectonic inversion may occur early in the Middle Permian and the response to tectonic activity is stronger in the southern West Junggar than in the northern West Junggar.