Rodinia Supercontinent Research Articles

Zircon SHRIMP U-Pb Dating and Significance From Weathered Residual Kaolin Deposits on the Northern Margin of the Qinzhou-Hangzhou Suture Zone, China

Weathered residual Kaolin deposits on the northern margin of the Qinzhou-Hangzhou Suture Zone are characterized by more feldspar-containing minerals and fewer dark minerals. These deposits have attracted increasing attention because of their high whiteness, low harmful impurity content, low depth of weathered mineralization, and ease for mining. The ore-forming rock masses mainly include granite (granite porphyry), quartz porphyry, eurite, haplite, and other acidic veins; the ore-bearing walls are mainly of Upper Proterozoic. Previous studies suggested that dyke rocks related to Kaolin deposits in this belt belong to the Mesozoic, but there is a lack of information regarding specific mineralization ages. In this study, two dyke wall-type weathered residual Kaolin deposits were selected from the northern margin of the Qinzhou-Hangzhou Suture Zone (Dongxicun and Yinbeidong, Jiangxi Province, China) for zircon SHRIMP dating. Two zircon U-Pb-based ages were obtained: 843 ± 10 Ma from Dongxicun granite veins that intrude into the Neoproterozoic Jiuling rock masses; 152.3 ± 1.8 Ma for Yinbeidong granite porphyry veins that intrude into the Neoproterozoic Anlelin Formation. We suggest that the dykes related to the Kaolin deposits were formed in the Neoproterozoic and late Jurassic. The Neoproterozoic dyke may be related to the convergence, formation, or pyrolysis of the Rodinia Supercontinent and the late Jurassic dyke may be related to the subduction of the Paleo-Pacific Plate. These results provide a chronological basis for the investigation and evaluation of weathered residual Kaolin deposits on the Qinzhou-Hangzhou Suture Zone.

Early Evolution of the Adelaide Superbasin

Continental rifts have a significant role in supercontinent breakup and the development of sedimentary basins. The Australian Adelaide Superbasin is one of the largest and best-preserved rift systems that initiated during the breakup of Rodinia, yet substantial challenges still hinder our understanding of its early evolution and place within the Rodinian supercontinent. In the past decade, our understanding of rift and passive margin development, mantle plumes and their role in tectonics, geodynamics of supercontinent breakup, and sequence stratigraphy in tectonic settings has advanced significantly. However, literature on the early evolution of the Adelaide Superbasin has not been updated to reflect these advancements. Using new detrital zircon age data for provenance, combined with existing literature, we examine the earliest tectonic evolution of the Adelaide Superbasin in the context of our modern understanding of rift system development. A new maximum depositional age of 893 ± 9 Ma from the lowermost stratigraphic unit provides a revised limit on the initiation of sedimentation and rifting within the basin. Our model suggests that the basin evolved through an initial pulse of extension exploiting pre-existing crustal weakness to form half-grabens. Tectonic quiescence and stable subsidence followed, with deposition of a sourceward-shifting facies tract. Emplacement and extrusion of the Willouran Large Igneous Province occurred at c. 830 Ma, initiating a new phase of rifting. This rift renewal led to widespread extension and subsidence with the deposition of the Curdimurka Subgroup, which constitutes the main cyclic rift sequence in the Adelaide Superbasin. Our model suggests that the Adelaide Superbasin formed through rift propagation to an apparent triple junction, rather than apical extension outward from this point. In addition, we provide evidence suggesting a late Mesoproterozoic zircon source to the east of the basin, and show that the lowermost stratigraphy of the Centralian Superbasin, which is thought to be deposited coevally, had different primary detrital sources.

The tectonic context of hafnium isotopes in zircon

The assembly and dispersion of continental crust are first-order controls on paleogeography and geochemical cycles. The associated reworking of Earth's crust can be tracked with zircon initial hafnium (εHfT) through space and time. Here we apply a new method of quantitative analysis using εHfT density estimates based on a compilation of 155,329 εHfT values. Investigation of the global database reveals significant geographic and temporal bias in the εHfT record associated with sampling and regional tectonic events. Recent research has attempted to address global εHfT bias using resampling methods to augment gaps of low εHfT data density, which in turn obfuscates tectonic signals and artificially weights outliers. Instead, we evaluate εHfT density patterns for both igneous and detrital zircon on eight continental zones demarcated by Paleozoic sutures: Africa, Antarctica, Asia, Australia, Baltica, North America, Peri-Gondwana, and South America. Pairwise two-dimensional quantitative comparison highlights similarity in timing and εHfT values between zones, all of which can be linked to documented shared regional tectonism. Integration of all pairwise comparisons reveals that peak similarity corresponds to the timing of supercontinent amalgamation, and that the associated εHfT differs depending on the style of supercontinent amalgamation, particularly internal versus external orogenesis. The three most recent supercontinents produced distinctive εHfT signals, shared by the constituent continental zones. The supercontinents Rodinia and Pangea were constructed through collisions of marginal arc terranes, peripheral to ancient crust, and did not produce highly enriched εHfT values. In contrast, Ediacaran to Cambrian formation of the Gondwana supercontinent was largely the product of internal Pan-African orogens that formed directly after Neoproterozoic Rodinia rifting and arc accretion forming the Arabian Shield. The final assembly of Gondwana was dominated by continent-continent collisions of old radiogenic crust without establishment and accretion of extensive intervening depleted arc terranes, resulting in a more enriched distribution of εHfT values compared to prior and subsequent supercontinent formation. The secular εHfT record is the product of spatiotemporally biased sampling and preservation of specific orogenic belts with predictable εHfT data arrays, modulated by the amalgamation, tenure, and breakup of supercontinents through time.

Proterozoic basin–orogen framework in the northern Tarim Craton, China

The Tabei Uplift is the oldest unit in the Tarim Basin, but its initiation and evolution are unclear, which restricts our understanding of the Neoproterozoic basin–orogen framework of the northern Tarim Craton, and the breakup process at the margin of the Rodinia supercontinent. In this study, we analyzed U–Pb age spectra of detrital zircons from sedimentary rocks of the Tabei Uplift and surrounding regions. By integrating these data of outcrops, wells, and seismic investigation, we identify spatial–temporal changes in Neoproterozoic sedimentary provenances, establish a geological framework of basin–orogen structure, and elucidate the long-term evolution of the Tabei Uplift.Five sedimentary rock samples were dated by zircon U–Pb geochronology to constrain their depositional ages and regional stratigraphic correlations. Precambrian strata of Well YL1 in the Yuli region belong to the upper Cryogenian–lower Ediacaran (ca. 660 Ma); Precambrian strata of the Sawapuqi region belong to the Ediacaran (ca. 595 Ma); and strata of the Wikiritag region belong to the middle Paleozoic (ca. 410 Ma).Analysis of 3962 zircons from these 5 new samples and 54 published Neoproterozoic samples reveals temporal and spatial variations in their U–Pb age spectra. From the periphery of the northern Tarim Craton to the Tabei Uplift for a given period (such as the Tonian Aksu Group, Cryogenian, and Ediacaran), the proportion of Neoproterozoic zircons decreases, whereas the proportion of Neoarchean–Paleoproterozoic zircons increases. From the Tonian to the Ediacaran for a given location, the proportion of Neoproterozoic zircons decreases, whereas the proportion of Neoarchean–Paleoproterozoic zircons increases. Combining this information with a Neoproterozoic wedge structure in the northern Tarim Craton observed in three geological/seismic profiles, the North Tarim Orogen and adjacent rift basin are inferred to have formed simultaneously during the Neoproterozoic. The Proterozoic North Tarim Orogen served as the provenance for surrounding regions in the northern Tarim Craton. We propose two main phases of Proterozoic orogenesis in the northern Tarim Craton, during the Paleoproterozoic and Neoproterozoic. The Paleoproterozoic orogen was initiated at ca. 1.9–1.8 Ga and terminated at ca. 1.8 Ga, whereas the Neoproterozoic orogen was initiated at ca. 900–740 Ma and terminated at ca. 600 Ma. The temporal–spatial evolution of the Neoproterozoic basin–orogen framework in the northern Tarim Craton was closely related to the breakup process at the margin of the Rodinia supercontinent.

A Tonian volcano-sedimentary succession in Newfoundland, eastern North America: A post-Grenvillian link to the Asgard Sea?

Abstract Early Tonian bimodal volcanic and sedimentary rocks (the Pine Pond succession) were identified in the Appalachians of eastern Laurentia for the first time, with U-Pb ages of igneous zircon at 951.4 ± 9 Ma for a felsic tuff and 952 ± 10 Ma for a crosscutting granite sheet. This Neoproterozoic succession is part of the East Pond metamorphic suite on the Baie Verte Peninsula (Newfoundland, Canada), which also contains 1491 Ma orthogneiss and is consistent with deposition over Mesoproterozoic basement in a pre-Iapetan extensional setting. Collectively, the data suggest a correlation with the southern Labrador Pinware terrane of the Grenville Province, where 1.52–1.46 Ga bedrock is intruded by 975–950 Ma granite. In addition, the age and location of this 952 Ma succession are consistent with deposition on the western margin of the Asgard Sea. Thus, the Pine Pond succession provides a link between key events in the assembly of the supercontinent Rodinia: the end of the Grenville orogeny, which led to the amalgamation of Laurentia and Amazonia, and the early Neoproterozoic evolution of the Asgard Sea, which separated Laurentia and Baltica.

Paleomagnetism of the Main South American Precambrian Cratons

Here, we discuss the role of the main South American cratonic units in the Columbia and Rodinia supercontinents, and Gondwana megacontinent. According to paleomagnetic and geological data Amazonia and West Africa were linked to Baltica, Laurentia and Siberia forming West Columbia at ca. 1.78-1.75 Ga. The 1.78 to 1.42 Ga paleomagnetic data for Amazonia, Baltica and Laurentia suggest either, that West Columbia preserved its integrity, at least, up to 1.42 Ga, or Amazonia/West Africa broke-up from West Columbia at some time between 1.53 and 1.42 Ga.. On the other hand, the Congo/São Francisco, North China, Rio de la Plata, India and proto-Australia formed the East Columbia at ca. 1.78 Ga. However, the presently available Paleo to Mesoproterozoic paleomagnetic data for these cratonic blocks suggest that East Columbia was short-lived. At 1.1 Ga ago, Amazonia/West Africa, Congo-São Francisco, Kalahari and India probably formed a megacontinent that later collided with Laurentia and Baltica forming Rodinia at ca. 1.0 Ga. Most probably, Rodinia broke-up at ca. 750 Ma, when Congo/São Francisco, Kalahari and other smaller blocks rotated ca. 90° counterclockwise, closing the Brasiliano/Clymene ocean and docked against Amazonia/West Africa and Rio de la Plata at ca. 600-570 Ma ago forming West Gondwana.

New Magnetic Anomaly Constraints on the Antarctic Crust

AbstractThe Antarctic Digital Magnetic Anomaly Project’s first‐generation magnetic anomaly map (ADMAP‐1) was produced for the region south of 60°S from about 1.5 million line‐kms of airborne and marine magnetic anomaly data (Golynsky et al., 2001; https://www.bas.ac.uk/data/our‐data/maps/thematic‐maps/admap‐magnetic‐anomaly‐map‐of‐the‐antarctic/). The second‐generation ADMAP‐2 compilation (Golynsky et al., 2017; https://doi.org/10.22663/ADMAP.V2) incorporated an additional roughly 2.0 million line‐kms of airborne and marine magnetic anomaly data from international mapping through 2015. The present study integrates satellite magnetic observations from the Swarm mission with the near‐surface data of ADMAP‐2 to help fill the regional coverage gaps and better define the altitude behavior of the Antarctic's magnetic anomalies for enhanced geological analysis. The resulting satellite magnetic data‐supplemented compilation, ADMAP‐2s, yields further constraints on the enigmatic geology of the Gamburtsev Subglacial Mountains, Prince Charles Mountains, Wilkes Land, Dronning Maud Land, and other poorly explored Antarctic areas. It offers insights on the global tectonic processes and crustal properties of the Antarctic and helps to unify disparate geologic and geophysical studies by linking widely separated outcrops. It also supports studies on the geological controls of the Antarctic ice sheet, the crustal transitions between Antarctica and the adjacent oceans, and the geodynamic evolution of the Gondwana and Rodinia supercontinents.

Evolution of eastern segment of the Central India Tectonic Zone: an insight from a magnetotelluric study

SUMMARYThe collision process between the South Indian Block (SIB) and North Indian Block (NIB) resulted in the development of the complex crustal nature of the Central India Tectonic Zone (CITZ). The evolutionary past of CITZ covers a long geological time (∼1000 Ma), which corresponds to the assembly and spreading of Columbia and Rodinia supercontinents. Despite several studies in the western and central parts of the CITZ, the location of the suture zone between the SIB and NIB is still under debate. In addition to that, the crustal structure in the eastern segment of CITZ is yet to be resolved. Therefore, for the first time, a dense station coverage magnetotelluric (MT) study is carried out along a 275 km transect in the eastern segment of CITZ from Pandaria to Rewa. The complexity of the Central Indian Shear (CIS) and Tan Shear Zone (TSZ) are reflected as anomalous phases (beyond 90°) in the MT data. A deep crustal resistivity model derived from 2-D and 3-D inversion of the MT data brought out a high-to-moderate conductivity structure (10–100 Ω-m) in the middle of the surface expressions of CIS and TSZ. The conductive structure could be related to a deformation zone formed by tectonic interaction of the CIS and TSZ or multiple tectonic boundaries in the middle of the CIS and TSZ. The conductive structure observed in the southern limit of the CITZ also may indicate the tectonic boundary between the SIB and NIB. The high conductivity in the deformation zone may be explained by the collision-related metallic rich sediments and/or mylonite associated with interconnected fluids. Moderately conductive vertical features delineated from the MT model correlate with the intrabasinal faults which might have acted as the pathways for Deccan volcanism. This study suggests that the CITZ could have been developed under the transition of oceanic subduction to continental collision processes at multiple geological times.

The newly discovered ca. 1.35 Ga metamafic rocks in the Oulongbuluke Block, NW China, and its record for transition from the Columbia to Rodinia supercontinent

Abstract The Oulongbuluke Block is an integral part of the Columbia and Rodinia supercontinents, but the lack of rock records from the transitional period between the Columbia and Rodinia supercontinents during the mid–late Mesoproterozoic has impeded our understanding of the tectonic relationship of the Oulongbuluke Block, which lies between the Columbia and Rodinia supercontinents. In this contribution, we present a systematic petrographic, geochemical, and zircon U-Pb-Hf investigation of newly discovered metamafic rocks in the Oulongbuluke Block. The results show that the metamafic rocks have a protolith age of ca. 1.35 Ga and an arcrelated metamorphic age of ca. 1.11–1.09 Ga. The metamafic rock samples are geochemically characterized by relatively high FeOT/MgO and FeOT and low SiO2, MgO, and K2O + Na2O, which shows tholeiitic affinity. These metamafic rocks exhibit slight light rare earth element (LREE) depletion and flat heavy rare earth element (HREE) content with no obvious Eu anomalies and slightly negative Nb, Sr, and Zr anomalies. These conditions are similar to those of enriched midoceanic-ridge basalt (E-MORB) and normal mid-oceanic-ridge basalt (N-MORB). The metamorphic rocks studied also have positive zircon εHf(t) values (2.96–7.04). Hence, the protoliths of the metamafic rocks may have been produced by variable degrees of melting of spinel-phase lherzolite mantle in a mid-oceanic ridge setting that was probably induced by a mantle plume. The presence of metamafic rocks indicates that the Oulongbuluke Block experienced the final breakup of the Columbia supercontinent at ca. 1.35 Ga, and the ca. 1.11–1.09 Ga arc-related metamorphism coincided with the convergence of the Rodinia supercontinent. The tectonic setting of the Oulongbuluke Block changed from a mid-oceanic ridge setting to an arc setting during the mid–late Mesoproterozoic, which was likely a response to the transition from the Columbia supercontinent to Rodinia supercontinent.

Age and provenance of the Precambrian Middle Timan clastic succession: Constraints from detrital zircon and rutile studies

The Precambrian sedimentary succession of Middle Timan provides important information on the coeval history of Baltica prior to assembly of the Rodinia supercontinent. This study comprises a comprehensive integrated provenance study based on samples collected from Precambrian clastic rocks of the Chetlassky Kamen and Volsko-Vymskaya Ridge. The maximum depositional age of the studied succession is constrained as latest Mesoproterozoic – earliest Neoproterozoic based on the youngest detrital zircon and rutile ages. Metasandstone samples within the succession are arkose, sublitharenite and litharenite. The distributions of detrital zircon U-Pb ages from the studied metasedimentary rocks are very comparable, yielding approximately 50% Mesoproterozoic ages within the ranges 1470 – 1550 and 1170 – 1370 Ma, 45% Paleoproterozoic ages and 5% Archean ages, with predominant populations grouping at 2500–2700 and 1800–1900 Ma. Comparable detrital zircon age distributions within the coeval strata of northern Baltica suggest a common provenance area. Analysis of detrital rutile suggests the widespread distribution of latest Mesoproterozoic – earliest Neoproterozoic metamorphism within the provenance area. A comparison of detrital zircon age distributions from the coeval strata of Baltica and Laurentia also revealed a striking similarity. Therefore, we suggest that clasts were in fact predominantly sourced from the Grenvillian-Sveconorwegian Orogen, with possible reworking of older zircon grains from older sedimentary rocks involved in the deformation and uplift. Our data support the tectonic model invoking a continuation of the Grenvillian-Sveconorwegian Orogen further to the east across the Barents Sea from its closest modern outcrop in Scandinavia.

Tectonic–sedimentary evolution during initiation of the Tarim Basin: Insights from late Neoproterozoic sedimentary records in the NW basin

Tectonic setting and sedimentary basin evolution during initiation of the Tarim Basin, China, are controversial, which restrain hydrocarbon explorations in the basin. Sedimentary stratigraphic framework is a key to reconstruct basin evolution and to determine the tectonic environment in which the basin has been formed. Here we, taking the northwestern Tarim Basin as an example, carried out a detailed investigation on the Neoproterozoic sedimentary records in the basin. The results shown that the NW Tarim Basin, during the Neoproterozoic era, was characterized by a paleogeographic evolutionary pattern of deep-water–glacial–littoral–platform facies, corresponding to an upward-thinning/fine sedimentary stratigraphic framework evolving from clastic rocks through mixed clastic-carbonate rocks to carbonate rocks. This stratigraphic sequence framework is comparable with the depositions of sedimentary basin obeying evolution path from syn-rifting during the pre-Cryogenian period, through rifting-to-depression transformation during the Cryogenian-early Ediacaran period, to syn-depression during the late Ediacaran period. The rifting–depression basin evolution path, may be of basin significances, implied that initiation of the Tarim Basin was in a continental rifting environment and was a long-term, continuous, pulsating process that proceeded at the same time as the global breakup of the Rodinia supercontinent.

Geochemical and zircon U-Pb-Hf isotopic study of volcanic rocks from the Yaolinghe Group, South Qinling orogenic belt, China: Constraints on the assembly and breakup of Rodinia

The tectonic mechanism responsible for the Neoproterozoic magma generation at the northern margin of the Yangtze craton is crucial to understanding the assembly and breakup of the Rodinia supercontinent. Here, we present a systematic study of the petrology, whole-rock geochemistry and geochronology of mafic and felsic volcanic rocks from the Yaolinghe Group, which outcrops mainly in the Shangnan area (north) and the Wudang area (south) of the South Qinling orogenic belt along the northern margin of Yangtze craton. Basalts from the Shangnan area are tholeiitic and calc-alkaline and indicated an arc environment. They have a LA-ICP-MS zircon U-Pb age of 847 ± 5 Ma with positive εHf(t) values of + 6.93 to + 8.79 and TDM1 model ages of 1130–1053 Ma. The rhyolites from this area exhibit geochemical characteristics similar to S-type granites and have a zircon U-Pb age of 841 ± 7 Ma, with a wide range of εHf(t) values of + 1.02 to −11.40 and TDM2 model ages of 2453–1674 Ma. This is different from the rhyolites from the Wudang area, which reveal geochemical affinities similar to A2-type granites, with a zircon U-Pb age of 788 ± 28 Ma, uniform negative εHf(t) values of −8.75 to −0.15 and TDM2 model ages of 2214–1663 Ma. Both rhyolites were sourced from partial melting of Paleoproterozoic crust with minor input of mantle material, but were formed in an arc setting and a post-collision extension setting, respectively. The 663–644 Ma mafic volcanic rocks from the Wudang area are enriched in Th, U, Nb and Ta, similar to oceanic island basalts and have positive zircon εHf(t) values ranging from + 9.24 to + 4.89 with TDM1 model ages peaking at 1018 Ma. They were derived from partial melting of an asthenospheric mantle source that had been modified by slab-derived melts and erupted during late Neoproterozoic continental rifting. Combining our results with existing data, we suggest that the South Qinling orogenic belt resulted from bidirectional subduction of the South Qinling Ocean between the Douling block and the Yangtze craton at ca. 950–750 Ma, accompanied by the formation of a trench-arc-basin system along the Douling block and an Andean-type continental arc belt at the northern margin of the Yangtze craton. After accretion, the amalgamated Douling block and Yangtze craton were affected by oceanic subduction of the Mirovoi Ocean at ca. 750–680 Ma, and subsequent continental rifting at ca. 680–620 Ma. The model further poses that the Yangtze craton was assembled to the periphery of the Rodinia supercontinent.

Neoproterozoic extensional basins and its control on the distribution of hydrocarbon source rocks in the Yangtze Craton, South China

• Neoproterozoic source rocks in the Yangtze Craton. • Structural and sedimentary patterns of the extensional basins evaluated. • The source rocks are related to the extensional basins, climate and life evolution. • Favorable areas for the source rock distribution are predicted. Hydrocarbon exploration in the Neoproterozoic extensional basins in the Yangtze Craton of South China has made prominent progresses in the past decades. However, the spatial distribution of source rocks across the craton still remains unclear. Here, we use outcrop observations, borehole data, and reflective seismic profiles to investigate the prototype, distribution and sediment infilling of these basins in the Yangtze Craton during the periods of source rock deposition. The basin prototype is categorized based on its tectonic origin and structural-sedimentary feature as follows. (1) During the deposition of the Datangpo Formation, rift basins extensively developed, band are characterized by a series of graben or half graben structures that consist of basin-controlling normal faults. The source rocks in the Datangpo Formation were deposited as the inner shelf basin or deep shelf facies, obtaining high thickness (i.e., 200 m) in the Wuling rift basin. (2) During the deposition of the Doushantuo Formation, the intracratonic rift basin and passive continental margin basin formed. These basins were controlled by syn-depositional faults that inherited the existing rift fault structures. The source rocks of the Doushantuo Formation were deposited as shelf lagoon, slope to deep-water basin facies. (3) During the deposition of the Dengying Formation, the intraplatform rift basin and passive continental margin basin developed with influence of regional tectonic extension. Not only are these basins affected by the preexisting faults, but also by the newly developed syn-depositional faults. The argillaceous source rocks of the Dengying Formation deposited as slope and deep-water basin facies. Further in-depth analyses revealed that a range of mechanisms may have contributed to the formation and distribution of source rocks in the Yangtze Craton, such as the break-up of the Rodinia Supercontinent, paleaolatitudes, glacial-interglacial geological events, basin extension and sedimentary environments. By integrating the distribution of the source rocks and the late tectonic reworking, this study predicts several targets for the source rock distribution in the Yangtze Craton, including in the central Sichuan, northeastern Sichuan, southern Shanxi, western Hubei, northeastern Guizhou-western Hunan, and the northeastern Guangxi-central Hunan areas.

The implication of two episodic Precambrian supercontinents convergence events from enriched mantle beneath the Yangtze Block: Constraints from the Zhangbaling mafic rocks

The Yangtze Block bears witness to a prolonged Precambrian evolutionary history and records the assembly of Precambrian supercontinents. Significantly, compared with the widely recognized ancient continental crustal growth and reconstruction, subduction-related mafic magmatism contains detailed possess of crust-mantle interaction in convergent plate boundaries. This paper reports Neoproterozoic mafic igneous rocks, represented by the 808–787 Ma amphibolites, from the Zhangbaling Uplift, northeastern sector of the Yangtze Block. Their prominent arc-affinity trace-element geochemical compositions with high concentration of LILE, the trough of Th, U, Zr and Hf in the spider diagram as well as natural δ18O values (5.3–6.5‰), indicate an interaction between the lithospheric mantle wedge peridotite and slab-derived fluids during early Neoproterozoic subduction event, and deficient in the involvement of felsic melts from crustal materials and sediments. Analyses of radioisotopes for amphibolites yield extremely low zircon εHf(t) (−25.3 to −3.6) and whole-rock εNd(t) (−17.1 to −10.4) values respectively, corresponding to an enriched mantle source. However, in consideration of the fact that the recycled slab-derived fluids is difficult to alter the isotopic composition (especially hafnium) of lithospheric mantle compared with its geochemical characteristics. Meanwhile, on the compilation of all Precambrian subduction-related magmatism in the Yangtze Block, it appears that the enriched isotopic signature in amphibolites is mainly inherited from the Paleoproterozoic (ca. 2.0 Ga) lithospheric mantle beneath the Yangtze Block, and extremely negative εHf(t) values (–25.3 to –18.4) further reflect prominent crust-mantle interaction correspond to the assembly of Columbia supercontinents. Therefore, the Zhangbaling mafic rocks witness the modification of lithospheric mantle by two episodic subduction events during Paleoproterozoic and Neoproterozoic respectively, which provide new evidence for the Yangtze Block to get involved in the reconstruction of Columbia and Rodinia supercontinents.

Petrogenesis and tectonic implications of Maoniushan monzogranites in the western margin of the Yangtze Block, Southwest China: Constraints from geochemistry, zircon U–Pb geochronology, and Hf–Nd–Sr isotopes

The Neoproterozoic granites along the western margin of the Yangtze Block are crucial for understanding the evolution of the Rodinia supercontinent and crust–mantle interaction. Based on a regional geological survey, this study analyses the zircon U–Pb geochronology, Lu–Hf isotope, whole‐rock Sr–Nd isotopes, and geochemistry of the Maoniushan granites along the western margin of the Yangtze Block and discusses the Neoproterozoic tectonic evolution history of the Mianning–Maoniushan belt. The results show that the Maoniushan granites belong to calc‐alkaline weak peraluminous monzogranite. The granites are enriched in large‐ion lithophile elements (i.e., Rb, Sr, Cs, and Ba) but relatively depleted in high‐field‐ strength elements (i.e., Nb, Ta, U, and Th). The zircon saturation temperature (TZr) ranges from 628 to 766°C, and the weighted average 206Pb/238U ages of zircon range from 771 ± 30 to 759 ± 26 Ma. The εHf(t) values range from −2.0 to +7.2, with TDM2 model ages ranging from 1,797 to 1,208 Ma. The whole‐rock Sr–Nd isotopic data show (87Sr/86Sr)i ratios of 0.7039–0.7093, and the εNd(t) values range from +1.25 to +1.76 with TDM2 model ages ranging from 1,303 to 1,344 Ma. These findings indicate the presence of deep Mesoproterozoic crustal materials in the source area. The Maoniushan monzogranites belong to I‐type granite, which is formed by the partial melting of the basic rocks and pelites in the ancient lower crust due to the metasomatism of fluids from the subducted oceanic crust. The Maoniushan monzogranites may be formed in the process of transformation from regional thickening to thinning under the oceanic crust subduction setting.

Mesoproterozoic magmatism redefines the tectonics and paleogeography of the SW Yangtze Block, China

The geodynamic setting of the Yangtze Block and its paleogeography in the reconstructed Rodinia supercontinent during the late Mesoproterozoic is loosely constrained due to the limited geological information reported. In this contribution, we identify a new suite of amphibolites in the SW Yangtze with an 1175 ± 5 Ma emplacement age. Geochemical modeling demonstrates they were derived from low-degree (3.5%–6.5%) partial melting of spinel lherzolite mantle. Additionally, three suites of late Mesoproterozoic granites in the SW Yangtze Block are revisited by providing new zircon U-Pb-Hf-O isotopes and whole-rock geochemical data. The granites have been dated to emplace during 1060–1042 Ma and have Zr + Nb + Y + Ce and Tzr values mostly at 304–576 ppm and 831–886 ℃, respectively, similar to A-type granites. Zircon Hf-O isotopic data indicate two subgroups of granites, in which one group has suprachondritic εHf(t) values of + 2.4 to + 11.4 with δ18O values of 6.5‰ to 7.4‰ while the other group has εHf (t) values of −3.9 to +1.5 with δ18O values of 10.0‰–11.6‰. The first group of granites was mainly derived from partial melting of mafic tholeiitic rocks while the second group of granites was mainly formed by partial melting of metasedimentary rocks. Integrated with published work, we propose that an intra-continental rift basin was developed in the SW Yangtze Block during ∼ 1.2–1.04 Ga, arguing against a late Mesoproterozoic orogenic event in the SW Yangtze Block. Statistical analyses based on compiled zircon U-Pb-Hf isotopes from Laurentia, Yangzte, and Amazonia show that the Yangtze has an isotopic affinity with west Nuna. These continents likely remained united during the transition from Nuna/Columbia to Rodina along the western periphery of the Rodinia supercontinent.

Geology, Petrographic Characteristics and Tectonic Structure of Paleoproterozoic basement of Kabul Block (North Eastern Afghanistan), Initial Findings

The Paleoproterozoic basement of Kabul Block is a cratonic basement in north eastern Afghanistan. Precambrian Kabul Block including metamorphic rocks only takes place at the base of the study area. The Neo-Proterozoic Welayati formation overlies the Paleo-Proterozoic Sherdarwaza formation with a tectonic contact, and they both overlay Khair Khana formation. In the region, Alghoi meta granitoid intruded into both Khair Khana and Sherdarwaza formations. The Khair Khana formation contains of granulites, granitic gneisses ve amphibolites. The mineral assemblages of granulites are plagioclase + quartz + K-feldspar + orthopyroxene + clinopyroxene (diopside/augite). Granitic gneisses are observed as hornblende gneiss, garnet-biotite gneiss and pyroxene-gneiss. Hornblende-gneisses include hornblende + quartz + K-feldspar mineral assemblage, garnet-biotite gneisses are evident with plagioclase + quartz + K-feldspar + biotite (red) + garnet mineral assemblage, and pyroxene gneisses include quartz + plagioclase + biotite + clinopyroxene mineral assemblage. Amphibolites consist of hornblende + plagioclase + quartz ± zoisite ± sphene ± ilmenite ± apatite mineral assemblage. The Sherdarwaza formation contains marbles, amphibolites, biotite gneisses, micaschists and migmatites. Marbles consist of calcites ± quartz ± apatite. In amphibolites, harnblende + plagioclase + quartz ± epidote ± zoisite ± garnet mineral assemblage are observed. Biotite gneisses include plagioclase + quartz + microcline + biotite ± sphene ± apatite ± zircon mineral assemblage. Micachists consist of quartz + plagioclase + microcline + biotite ± sphene ± apatite mineral assemblage. Migmatites include plagioclase + quartz + microcline +biotite ± sphene ± apatite mineral assemblage. Alghoi meta granitoid is generally observed as stocks and small masses, and sometimes it shows foliation. It consists mainly of meta granites. The meta granites that show granular texture include plagioclase + quartz + K-feldspar + biotite + hornblende. The Welayeti formation contains quartzite, kyanite-garnet-staurolite schist, garnet-mica schist, kyanite-garnet-mica schist and garnet-muscovite schist. Quartzite include quartz ± muscovite ± biotite. They are observed hornblende + quartz + plagioclase ± garnet ± epidote ± zoisite ± rutile ± magnetite in amphibolites. Kyanite-garnet-staurolite schists are evident with staurolite + kyanite + garnet + mica + biotite + quartz + plagioclase ± apatite ± epidote ± ilmenite ± monazite mineral assemblage. Garnet-mica schists and kyanite-garnet-mica schists include quartz + plagioclase + biotite + muscovite + kyanite + garnet ± chlorite ± apatite ± tourmaline ± sphene ± rutile. In garnet-muscovite schists, muscovite + quartz + plagioclase + garnet ± tourmaline ± apatite ± zircon are observed. The granulites in Kabul Block are together with granite gneisses, and they can be separated under one formation. Granulites show different mineral compositions, Usually, they are without garnet, in some cases they include garnet. The amount of plagioclase is higher in them according to other rocks. In some cases, the composition of granulites is very similar to that of quartz mangarites that indicates high temperature and pressure of the metamorphism process and shows that this block is related to a segment of Columbia and Rodinia supercontinents during Paleoproterozoic collisional events.

Neoproterozoic A-type granites in northern Beishan Orogenic Belt: Early response of the Rodinia supercontinent break-up

Neoproterozoic A-type granites in northern Beishan Orogenic Belt: Early response of the Rodinia supercontinent break-up

Tectonic Evolution of the Neoproterozoic Tusham Ring Complex, Northwestern India: Constraints from Geochemistry and Zircon U-Pb Geochronology, and Implications for Rodinia Supercontinent History

Tectonic Evolution of the Neoproterozoic Tusham Ring Complex, Northwestern India: Constraints from Geochemistry and Zircon U-Pb Geochronology, and Implications for Rodinia Supercontinent History

ХАНКАЙСКИЙ МАССИВ: ГЕТЕРОГЕННОСТЬ ФУНДАМЕНТА И РЕГИОНАЛЬНЫЕ КОРРЕЛЯЦИИ

The results of geochronology studies on metagranitoids (U-Pb SIMS) and ophiolites (Sm-Nb) from the Khanka massif are considered. New and published data define the Early Neoproterozoic Matveevka-Nakhimov terrane with early suprasubduction magmatism of 935 and 915 Ma, intraplate and Pacific-type transform margin magmatism of 850-880 and 757 Ma, and the Late Neoproterozoic-Early Cambrian Dvoryan and Tafuin terranes with suprasubduction magmatism of 543, 520, 517 and 513 Ma. Between these two parts of the massif there is a suture (Voznesenka and Spassk terranes) formed by Ediacaran-Cambrian shelf deposits and a Cambrian accretionary prism with ophiolites older than 514 Ma. The greater part of the Khanka massif formed late in the Cambrian with the Kordonka island arc terrane accreted at the end of the Silurian. The Sergeevka terrane of the Ordovician island arc joined it through Early Cretaceous strike-slip movements. Heterogeneous structures of the main part of the Khanka massif can be traced to the north by the analogous stages of magmatism and metamorphism, where the Jiamusi massif (including the East Bureya terrane) is an Early Neoproterozoic block and the eastern Songnen massif (including the West Bureya terrane) is a Late Neoproterozoic-Cambrian block. Between these two blocks is the Spassk-Wuxingzhen-Melgin suture formed by their collision late in the Cambrian. The Bureya-Songnen-Jiamusi-Khanka superterrane formed as a part of the Gondwana supercontinent about 500 Ma ago through orogeny and accretion of the Rodinia supercontinent fragments.