Rift Research Articles

Two episodes of mid-Neoproterozoic mafic magmatism in the Hong'an Terrane, Central China: Records of continental rifting during the breakup of the Rodinia supercontinent

The mid-Neoproterozoic (800–635 Ma) tectonic regime along the northern margin of the Yangtze Block is still debated, particularly the timing and mode of transition from a subduction-related setting to a rifting-related setting. The new identification of two episodes of mafic magmatism, represented by (I) 736–710 Ma Daleishan and (II) 635 Ma Hong'an intrusions in the Hong'an Terrane, central China, provides new constraints on the nature of their mantle source and tectonic evolution of the northern Yangtze Block. (I) Daleishan mafic rocks are tholeiitic in composition and exhibit N-MORB- to arc-like trace element patterns. They have variable whole-rock initial 87Sr/86Sr (0.7041 to 0.7092), εNd(t) (−2.98 to +2.17), and εHf(t) (+3.37 to +10.25) values. Their magmatic zircons preserve relatively homogeneous δ18O (+4.50 to +6.01 ‰) and highly variable εHf(t) (+1.3 to +13.1) values. Chemical compositions and modeling results suggest that Daleishan rocks were derived from a depleted asthenospheric mantle source with involvement of recycled sediment component, and the magma subsequently underwent 5–15% contamination by the wall-rocks during its emplacement. (II) Hong'an mafic rocks mainly show E-MORB- to arc-like geochemical features with more enriched HfNd isotopes [zircon εHf(t) = −3.0 to +3.6; whole-rock εNd(t) = −6.87 to −0.75, and εHf(t) = −0.50 to +2.00], suggesting they were derived from the interactions between the asthenosphere and the previously-metasomatized lithospheric mantle. Integrating the new data with previous results for the Neoproterozoic rocks in the northern margin of the Yangtze Block (including the Qinling-Dabie orogen), we emphasize that episodic extension-related asthenosphere upwelling in a continental rifting setting, coupled with interactions between the asthenosphere and the lithosphere, played a prominent role in the formation of the 780–635 Ma bimodal-type magmatic rocks and diverse geochemical features in the mafic counterparts.

Landslide Mapping and Causes of Landslides in the China–Nepal Transportation Corridor Based on Remote Sensing Technology

The China–Nepal Transportation Corridor is vital to the country’s efforts to build a land trade route in South Asia and promote the Ring-Himalayan Economic Cooperation Belt. Due to the complex geological structure and topographical environment of the Qinghai–Tibet Plateau, coupled with the impact of climate change, the frequent occurrence of geological disasters has increased the operational difficulty of the China–Nepal Highway and the construction difficulty of the China–Nepal Railway. However, to date, there has been no systematic study of the spatial distribution of landslides along the entire route within the area, the factors influencing landslides at different scales, or the causes of landslides under different topographic backgrounds. There is an even greater lack of research on areas threatened by potential landslides. This study comprehensively applies remote sensing, mathematical statistics, and machine learning methods to map landslides along the China–Nepal transportation corridor, explore the influencing factors and causes of different types of landslides, and investigate the distribution characteristics of potential landslides. A total of 609 historic landslides have been interpreted in the study area and were found to be distributed along faults and locally concentrated. The strata from which landslides develop are relatively weak and are mainly distributed within 2 km of a fault with a slope between 20° and 30°. The direction of slope for the majority of landslides is south to south-west, and their elevation is between 4000 and 5000 m. In addition, we discovered a power law relationship between landslide area and volume (VL = 2.722 × AL1.134) and determined that there were 47 super-large landslides, 213 large landslides, and 349 small and medium-sized landslides in the area, respectively. Slope is the most significant influencing factor for the development of landslides in the area. Apart from slope, faults and strata significantly influence the development of large and medium-small landslides, respectively. We have identified 223 potential landslides in the region, 15 of which directly threaten major transport routes, mainly in the Renbu Gorge section of the China–Nepal Highway and the proposed China–Nepal Railway section from Peikucuo to Gyirong County. In addition, we also discussed the causes of landslides within three geomorphic units in the region. First, the combined effects of faulting, elevation, and relatively weak strata contribute to the development of super-large and large landslides in the Gyirong basin and gorge. Second, the relatively weak strata and the cumulative damaging effects of earthquakes promote the development of small and medium-sized landslides in the Xainza-Dinggye rift basin. Third, under the combined effect of the hanging wall effect of thrust faults and the relatively weak material composition, landslides of various types have developed in the Nagarzê mountain. It is worth noting that potential landslides have developed in all three geomorphic units mentioned above. This study provides data and theory to assist in the accurate mitigation and control of landslide hazards in the corridor.

Predicting the thermal maturity of source rock from well logs and seismic data in basins with low-degree exploration

Vitrinite reflectance (Ro) is a significant geological index that evaluates the thermal maturity of source rock. However, measured Ro data and suitable evaluation methods are lacking, making it difficult to predict the thermal maturity of source rock in basin, especially in those with a low exploration degree. In this study, we propose a novel method for estimating Ro from well logs and seismic data using seismic velocity inversion and the vitrinite reflectance-mudstone porosity (Ro-ϕ) model. First, using a wavelet neural network, acoustic transit time curve was reconstructed from spontaneous potential, gamma rays, resistivity, and density logs, and new curve was used as inputs in a colored inversion to obtain seismic relative velocity. Second, a low-frequency model was established to counteract critical frequency and sequence framework constraints. Third, the seismic absolute velocity was merged by relative and low-frequency velocity components. Finally, Ro distributions were calculated using the Ro-ϕ model. Our findings indicate that the inversion effect improved with low-frequency supplement; compared with the graphic and geochemical method, the Ro-ϕ model predicted Ro in poor-data areas more accurately, with a relative error of <9.5205%. We also propose an explanation for the appearance of highly mature source rocks distributed from dispersion to aggregation in depression-rift transitions: the thick stratum in the downthrow wall of boundary faults promote source rock maturity in the rift period; hence, in an open depression, the source rocks in large subsidence areas are highly mature, particularly near the downthrow wall of a boundary fault, which has the highest maturity owing to the superimposed subsidence of the overlying rifted basin.

The Precambrian continental record: A window into early Earth environments

The Precambrian was characterized by unique palaeoenvironmental conditions in the Earth’s atmosphere, biosphere and geosphere. This study presents a global quantitative analysis of Precambrian sedimentary successions of aeolian, alluvial, fluvial, lacustrine and glacigenic origins, examined in the broader context of Earth evolution. In the Precambrian, an apparent scarcity of aeolian successions is observed. This may be linked to: (1) differences in atmospheric density, which controlled wind erosion and sedimentation; (2) different astronomical configurations, which may have influenced tides and atmospheric circulation, thereby affecting sand availability and the width of subtropical zones; (3) potentially hotter and more humid climates, restricting dry-sand availability; (4) a lack of vascular vegetation that could prevent reworking of aeolian deposits; (5) poor preservation potential; (6) misinterpretation of the Precambrian record. Mixed aeolian-alluvial strata are more abundant, perhaps because their preservation in the geological record was favoured by water tables sustained by incursions of alluvial systems into otherwise aeolian dominated environments. Aeolian deposits were preferentially accumulated during phases of supercontinental breakup, where rapidly subsiding rift basins provided accommodation suitable for preservation. Other than in the Neoproterozoic record, where glacigenic deposits dominate, alluvial strata are the most common and thickest type of continental deposit in the Precambrian. Precambrian braided alluvial systems were more widespread than in the Phanerozoic. Major alluvial systems formed preferentially during phases of supercontinent assembly, whereby alluvial systems drained major orogens, and long drainage pathways developed from supercontinent interiors to coastlines. In the Paleoproterozoic, ephemeral, saline to partly arid lakes developed extensively in the desertic interior of Columbia. Glacial deposits preferentially formed in the breakup phase of supercontinental cycles; this supports theories invoking enhanced chemical weathering of uplifted rift shoulders as a driver of carbon dioxide sequestration, global cooling, and glaciation. Overall, the number of identified continental successions increases towards the Precambrian-Phanerozoic boundary. This may be an artefact of an increasingly more complete stratigraphic record as time progresses. However, the abundance of continental successions varies on a quasi-periodic cycle of 500 – 700 Myr, with peaks coinciding with the tenure and breakup of Precambrian supercontinents.

Correlating mantle cooling with tectonic transitions on early Earth

Abstract The dominant tectonic mode operating on early Earth (before ca. 2.5 Ga) remains elusive, with an increasing body of evidence suggesting that non-plate tectonic modes were likely more prevalent at that time. Thus, how plate tectonics evolved after that remains contentious. We performed two-dimensional numerical modeling of mantle convection at temperatures appropriate for the Hadean–Archean eons and show that subduction and rift systems may have spontaneously emerged on Earth from an earlier drip-and-rift–dominated tectonic mode in response to the secular cooling of the mantle. This cooling of the mantle was mediated by repeated events of rifting and dripping that likely occurred over a few hundred million years. As the mantle cooled, its effective viscosity and the thickness and strength of the lithosphere increased, which helped establish rigid plates and initiate plate tectonics on Earth.

Revisiting the stratigraphical, sedimentological and provenance evolution of Lingshan Island, offshore of east China: Implications for the destruction of the north China craton

The Cretaceous strata of Lingshan Island, offshore of East China, are a key sedimentary archive for understanding the destruction of the North China Craton (NCC). However, there has been limited progress in characterizing its stratigraphical, sedimentological and provenance evolution in the context of the progressive lithospheric thinning and magmatism associated with the destruction of the NCC. We report field logging data, sandstone framework petrography, and detrital and volcanic zircon U–Pb geochronology data from the Cretaceous strata of Lingshan Island, and correlate these data with coeval sediments in the Jiaolai Basin and volcanic units in the East China. Our results indicate rapid deposition of the Laiyang and Qingshan groups from c. 124–123 Ma with an upward thickening and coarsening succession from the lacustrine turbidites of the Laiyang Group to the deltaic rocks of the Qingshan Group, accompanied by an increase in volcanic activity up-section. Sandstone petrology and detrital zircon U–Pb ages indicates that the source areas for the Laiyang and Qingshan Groups were syn-depositional volcanic rocks and plutonic rocks, with some contributions from the Yangtze Craton and Sulu terrane. Our compilation of detrital zircon U–Pb ages (n = 8513) from the Cretaceous strata of Lingshan island and the Jiaolai Basin in the hinterland implies provenance contributions from four different sources. The zircon Th/U ratios from this large dataset suggests that Cretaceous magmatic zircons formed in an extensional setting (Th/U ratios >1 but with significant variation). The Eu anomalies in magmatic zircons (n = 550) from the Jiaodong Peninsula indicate continuous lithospheric thinning in Eastern China since c. 130 Ma, leading to the destruction of the NCC. Based on all available data, Lingshan Island most likely was a rift basin during the Cretaceous.

Carbonate production and reef building under ferruginous seawater conditions in the Cambrian rift branches of the Avalon Zone, Newfoundland

AbstractThe characterization of carbonate production on rift basins is critical for understanding the nucleation and demise of reefs in tectonically active areas. A new petrographic and mineralogical analysis of Cambrian strata from the Avalon Zone in Newfoundland, based on scanning electron microscopy – back‐scattered electron detector and Raman spectrometer analyses, facilitates recognition of several episodes of Terreneuvian–Miaolingian carbonate production and associated precipitation of ironstone and phosphorite. These distinct units mainly developed on uplifted rift shoulders and basaltic lava palaeoreliefs, and reflect amalgamated high‐energy events, interrupted by scouring discontinuities (diastems) commonly lined by phosphatized and ferruginized microbial crusts. Mud‐mounds, in contrast, nucleated under calm conditions episodically punctuated by high‐energy episodes, where scattered thromboid structures occur as both clotted textures and distinct calcimicrobes. Precipitation of hematite/goethite versus chamosite couplets, both occluding primary porosities and replacing interlaminae and cortices of oncoids and coated aggregates, point to marine substrates close to the Fe‐redox boundary. Upwelling of phosphate‐rich ferruginous hydrothermal waters contributed to the precipitation of ironstone and phosphate interbeds. Ferruginous waters related to penecontemporaneous hydrothermal activity, reflected by the record of synsedimentary fissuring and stockwork ore bodies, were delivered to confined rift‐related horst‐and‐graben settings, largely controlled by the development of specific Cambrian carbonate and associated ironstone facies. The influence of ferruginous waters necessarily affected the record of climatically sensitive evaporitic pseudomorphs, reefs/mounds and phosphorites, which are then not suitable criteria to discriminate palaeolatitude, as demonstrated by a comparison of low‐latitude to middle‐latitude margins fringing Baltica, and the Avalonian and Atlas – Ossa‐Morena – Northarmorican rift transects of West Gondwana.

Provenance history, depositional conditions andtectonic settings during late Cenomanian – early Turonian time in the Gongola Sub-Basin of the Upper Benue Trough Nigeria: Evidence from major and trace elements geochemistry of the Kanawa shales from the Pindiga Formation

Newly analysed major and trace element compositions of the Kanawa shales deposited in the Pindiga Formation reveal the provenance history and depositional conditions during the late Cenomanian - early Turonian time in the Gongola Sub-Basin of the Upper Benue Trough. We conclude that the source of the siliciclastic detritus in the Kanawa shales of the Pindiga Formation are igneous rocks of predominantly intermediate chemistry with a temporal trend towards more felsic compositions. The source rocks presumably underwent intense chemical weathering with CIA, PIA and CIW values up to 89.51, 97.30, and 97.56, respectively, which led to enhanced shale deposition in the Gongola Sub-basin. Obtained relatively high Fe/Mn and Zr/Rb ratios in the Kanawa shales suggest deposition under relatively strong hydrodynamic conditions in presumably shallow water. Additionally, integrated bivariate plots of Ga/Rb vs. K2O/Al2O3, SiO2 vs. Al2O3+K2O + Na2O with the ratios of Sr/Ba, Rb/K, MgO/Al2O3x100, V/Cr, V/(V + Ni) V/(V + Cr), P/Ti and Ba/Ti indicate deposition under a warm, humid climate in dominantly anoxic and brackish water conditions under relatively low primary productivity conditions. This interpretation aligns with the global climate and redox conditions during the late Cenomanian – early Turonian times. The tectonic setting bivariate diagrams of K2O/Na2O vs. SiO2 and SiO2/Al2O3 vs. K2O/Na2O, as well as the high and low quartz multidimensional diagrams, reveal a rift basin in a passive margin depositional environment, confirming earlier works on the evolution of the Benue Trough.

The impact of Oligo-Miocene basaltic intrusions on the petroleum system in Gulf of Suez rift basin, Egypt: new insights into thermal maturity and reservoir quality

In recent years, the petroleum industry has prioritized the exploration of new and unconventional petroleum reservoirs. As a result, this study assessed the significance of basaltic intrusions from two key aspects: their impact on the thermal maturity of pre-rift source rocks and their potentiality as reservoirs. The present study attempts to integrate surface field investigations of basaltic dykes in Wadi Nukhul and Wadi Matulla as surface analogs with petroleum system modeling of pre-rift source rocks containing subsurface basaltic intrusions in the Abu Rudeis-Sidri field. Therefore, the fracture networks were observed in Wadi Nukhul and Wadi Matulla, suggesting that both the basaltic dykes and host rocks have interconnected fractures, which is critical for a high-quality reservoir of the dykes and efficient oil expulsion. As a result, the analysis of burial history, temperature, maturity, generation, transformation ratio, and expelled oil quantity revealed a significantly high value for basaltic intrusions. Moreover, the Abu Rudeis-Sidri field had a good petroleum system with thermally mature source rocks by basaltic intrusions. Furthermore, the fractured basaltic intrusions presented a high-quality oil reservoir well-sealed by the thick Rudeis Formation. Oil production has doubled since the discovery of this reservoir. This study introduces a novel approach to understanding the distribution pattern of basaltic intrusions in subsurface and surface analogs, which can serve as a model for exploring new potential unconventional basaltic reservoirs in the Gulf of Suez rift basin.

The origin and tectonic evolution of the late Neoproterozoic rift basin in the Tarim Craton, NW China

The Cryogenian-early Paleozoic succession in the Tarim Craton is generally regarded as a continuous rift sequence that followed the prolonged superplume-related breakup of Rodinia. However, the rift architecture and origin of the late Neoproterozoic basin are poorly known, but these are important for the understanding of the tectonic evolution of the basin and for the evaluation of the hydrocarbon potential. This paper aims to elucidate the rift architecture, distribution, origin and evolution of the late Neoproterozoic Tarim Basin by integrating outcrop investigations with well and seismic data. The late Neoproterozoic magma-rich active rifting primarily occurred in the northeastern part of the basin, whereas other areas experienced slightly younger magma-poor passive rifting. The Ediacaran succession overlaps in the northern basement uplift to show a pre-Ediacaran unconformity occurs in the northern Tarim Craton, while a sub-Cambrian unconformity traverses the entire Tarim Craton and presents a distinct truncation in the southern basement uplift. A tiered architecture exists in which narrow, deep Cryogenian grabens are overlain by a broad Ediacaran depression. Two NE-striking rift systems developed in the northeastern and southwestern Tarim. It can be inferred from the compiled data that the late Neoproterozoic rift basin evolution in the Tarim Craton can be divided into four stages: early Cryogenian rifting, late Cryogenian fault-graben, Ediacaran intracratonic depression, and end-Ediacaran regional uplifting. These results suggest that documented Neoproterozoic retreating subduction-related slab failure/detachment processes led to both active and passive rifting, which contributed to the diverse continental rift architecture and evolution of the late Neoproterozoic Tarim Basin.

Sequence Stratigraphic Analysis of the Volcanic Rock–Evaporite–Clastic Rock Symbiotic Zone in the Fourth Member of the Shahejie Formation in the South of Laizhou Bay

Laizhou Bay Sag is a typical continental rift lake basin, which is affected by strike–slip activity, salt rock activity, volcanic activity, and paleoclimate change in the Tanlu fault zone, where three major lithologies—volcanic rock, clastic rock, and evaporite—mainly develop. In order to determine the sequence correspondence between the different lithologies in the study area based on drilling, logging data, and seismic data, it is determined that the fourth member of the Shahejie Formation in the southern Laizhou Bay mainly develops three types of sequences: clastic rock type sequences, salt lake type sequences, and volcanic rock/clastic rock type sequences. Two second-order sequence boundaries (SBs3L, SBs4L) and one third-order sequence boundary (SBs4U) were identified, and the principle of three divisions of system tracts (LST, TST, HST) and sedimentary processes in different types of sequences were determined by analyzing the stacking patterns of different sequences. Compared with the previous research results, this study provides a more detailed analysis of the sequence boundary definition of different blocks and different lithologic strata, and it improves the previous general sequence stratigraphic division method. Based on the study of distinct types of sequences, a unified stratigraphic framework is established in the whole zone, and the stratum thickness distribution of the fourth member of Shahejie Formation is smaller in the southwest and larger in the northeast. The study area is generally filled with pyroclastic rocks–evaporite–clastic rocks, changing from fan delta–saline lake filling to braided river delta–freshwater lake–fan delta filling from bottom to top. A sequence stratigraphic model for the comparison of steep slope–gentle slope differences is established to provide guidance for future oil and gas field exploration and development.

Controls on organic matter enrichment of the early-middle Miocene lacustrine oil shale, central Tibet (SW China): New insights from clay minerals and geochemistry

The Lunpola oil shale is the largest lacustrine oil shale deposit in Tibet (SW China), which deposited in a Cenozoic lacustrine rift basin and contains abundant organic matter (OM), whereas the crucial factors that controlled the OM enrichment remain elusive. Here, we present new datasets of total organic carbon (TOC) contents, clay minerals and whole-rock geochemistry of the early-middle Miocene Middle Dingqinghu Formation oil shale from the Lunpola basin, central Tibet, in order to elucidate the paleoclimate, paleo-environment condition and the controlling factors on the OM enrichment of the lacustrine oil shale.Oil shales from the Lunpola East section have high TOC contents (avg. 9.60%), while the contiguous mudstones contain low TOC contents (avg. 0.44%). During the oil shale deposition, high smectite and kaolinite contents, low illite contents and low Sr/Cu ratios suggest strong chemical weathering and hence warm and humid climate, which may probably have close relationship with the mid-Miocene climatic optimum (MMCO). However, during the mudstone deposition, the relatively high illite and low smectite contents and higher Sr/Cu ratios suggest weak chemical weathering, indicating relatively arid climatic condition. The paleo-environment indexes (Corg/P, MoEF and UEF) and MoEF-UEF covariation reflect an anoxic bottom water condition during the oil shale deposition, while the mudstone formed in oxic-dysoxic water environment. The weak and moderate positive relationship between bio-productivity proxies (P/Ti and Cu/Ti ratios) and TOC contents reveal that the bio-productivity condition is not the crucial factor for the OM enrichment. Moreover, the water column environment was brackish and stratified during the oil shale deposition, and the sedimentation rate was moderate, which were also conducive to the OM preservation. The positive correlations between the TOC and the paleoclimate and paleoenvironment proxies demonstrate that warm and humid climate during the MMCO and anoxic water conditions play predominant roles in OM enrichment of the Lunpola lacustrine oil shale. Besides, modest sedimentation rate can prevent the dilution of OM, which can also promote the OM enrichment. This study can not only deepen the understanding of OM enrichment mechanism in lacustrine rift basin but also provide important information for predicting the distribution of the oil shale in the Lunpola Basin.

Upper Cambrian–Lower Ordovician conodonts from the southern margin of the Kopet-Dagh Basin, Saluk Mountains, Iran

A detailed Furongian to Tremadocian conodont biostratigraphy is established from the Saluk Mountains located in southern Kopet-Dagh, northeast Iran. Thirty species assigned to 17 genera were recovered from decimetre-scale limestone beds in a fine-grained siliciclastic succession, deposited in an intraplate rift system. The following biozones are established for the region, in ascending order: Proconodontus muelleri, Eoconodontus, Cordylodus intermedius, Cordylodus lindstromi, Cordylodus angulatus, Paltodus deltifer and Acodus triangularis interval zone. This low-to medium-richness conodont fauna comprises cosmopolitan euconodont species of Proconodontus, Eoconodontus, Cordylodus, Teridontus nakamurai, Semiacontiodus nogamii and a few long- ranging proto- and paraconodont species, which inhabited a narrow marine basin flanked by landmasses and formed by active rifting. It lacks shallow water tropical taxa and probably belongs to the Cold Domain of the Shallow Sea Realm. The occurrence of conodonts of the Paltodus deltifer Biozone in the uppermost part of the Qyzlar Formation in the Ghelli section suggests that the major episode of flood basalt volcanism in south Kopet-Dagh commenced in the late Tremadocian. Hadi Jahangir [Jahangir.hadi@nigpas.ac.cn] and Guanzhou Yan [gzyan@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, PR China.

Sedimentology and chronostratigraphy of the Apt Basin, Southeastern France: lacustrine response to late Paleogene cooling and regional rifting

The Apt Basin, sub-basin of the wider Manosque Basin of southeastern France, contains deposits of Eocene-Oligocene lake systems that were part of a broader network of evaporative lakes and lagoons spread across the European Cenozoic rift system. The onset and mechanisms of subsidence in the rift system, the interconnectivity of these lakes, and their response to the transition into the Oligocene icehouse are poorly understood. This study aims to clarify these points by examining the stratigraphy and depositional environments in the Apt Basin. We correlate and date Eocene to lowermost Oligocene geological units using a basin-wide facies model combined with sedimentological and geochronological approaches. We show the existence of three lacustrine phases, each separated by complete lake drying events: (1) an Ypresian (?) − Lutetian lake-marsh system dominated by palustrine carbonates; (2) a Bartonian (?) − Priabonian siliciclastic fluvio-deltaic and saline lake system; and (3) a lower Rupelian saline carbonate lake system. The presence of a lake system during the Ypresian (?) − Lutetian suggests an onset of basin subsidence before most other basins of the rift system in southeastern France, and is associated with the late Pyrenean deformation phase. The initiation of the second lacustrine phase marks the beginning of E-W extension and the formation of the Apt Basin as an individual horst &amp; graben system. Based on facies distribution, we demonstrate the hydrological isolation of the Apt Basin from other basins and the improbability of any marine connection during the first two phases. This isolation is less certain for the third phase. We show a close synchronicity between the second lake drying event and the Eocene-Oligocene Transition. The third lacustrine phase, dominated by carbonate production and low siliciclastic input, is interpreted as reflecting a long-term decrease in surface runoff associated with the fall into the Oligocene icehouse.

Magma‐Assisted Continental Rifting: The Broadly Rifted Zone in SW Ethiopia, East Africa

AbstractThe Gofa Province and Chew Bahir Basin in the Broadly Rifted Zone (BRZ) between the southern Main Ethiopian Rift (sMER) and the northern Kenya Rift (nKR) record early volcanism and associated faulting in East Africa; however, the spatiotemporal relationships between volcanism and faulting remain poorly constrained. We applied apatite (U‐Th)/He (AHe) and zircon (U‐Th)/He (ZHe) thermochronometry to Neoproterozoic basement rocks from exhumed footwall blocks of the extensional Gofa Province and Chew Bahir Basin, and analyzed our result in the context of well‐dated regional volcanic units in the BRZ to unravel the interplay between tectonic exhumation, faulting and volcanism. Single‐grain AHe ages ranging from 1.0 to 136.8 Ma were recorded in 32 samples, and single‐grain ZHe ages from three samples range between 142.2 and 335.6 Ma. The youngest AHe ages were obtained from the Chew Bahir Basin and the narrow deformation zone in the Gofa Province. Our thermal modeling results reflect little or no significant regional crustal cooling prior to extensive volcanism, which started at about 45 Ma. Conversely, new and previously published thermal history models suggest that widespread crustal cooling related to regional extension occurred between ∼27 and 20 Ma. Thermal modeling results from subsets of samples indicate that following this initial diffuse extensional deformation, renewed exhumation occurred along a narrow zone within the Gofa Province and the Chew Bahir Basin during the middle to late Miocene (15‐6 Ma) and Pliocene (&lt;5 Ma), respectively. The crustal cooling phases follow a regional trend in volcanic episodes. For example, initial cooling between 27 and 20 Ma corresponds with the end of widespread flood‐basalt volcanism (45–28 Ma), suggesting that spatially diffuse normal faulting may have initiated shortly after the emplacement of voluminous and areally extensive flood basalts. The Miocene and Pliocene shifts in deformation along the Mali‐Dancha and Bala‐Kela basins in the Gofa Province and the Chew Bahir Basin, respectively, may indicate strain localization during the late stage of rifting and ongoing tectonic interaction between the sMER and the nKR. Our results support the notion of crustal weakening by massive volcanism as a precursor to widespread extensional faulting, and thus offer further insights into magma‐assisted deformation processes in the East African Rift System.

Temporal and spatial distribution and genesis of primary indium deposits around the world

Because rare dispersed elements including indium play an increasingly extensive and indispensable role in the field of modern high technology, the exploration, development and research of its resources are in full swing. The abundance of indium in the earth's crust is extremely low, and its original independent deposits have not been found so far. Indium is mainly parasitic in bulk non-ferrous metal deposits in the form of associated by-products. Because of its origin, the genetic types of indium deposits are as diverse as those non-ferrous metal deposits it parasitizes. The distribution of indium in geological time and earth space is uneven. The formation of indium ore deposit is closely related to tectonic-magmatic activity. It is the product of plate tectonic movement, continental rifts and mantle plumes or mantle hotspots in the interior of ancient continents. The emergence of indium ore deposit is inseparable from magmatic activity, especially granite magmatic activity. Ore-forming materials mainly come from the upper mantle and/or deep crust. Indium deposits formed under high temperature conditions have enrichment mechanisms. In addition to the enrichment factors of traditional metal deposits, the enrichment of nano-scale indium minerals through the nano effect is also a very important enrichment method. The indium deposits formed at the end of the differentiation and evolution of granite magma may not be enriched in one go, but is the result of multiple enrichments.

Mesoproterozoic Strike-Slip Faulting within the Åland Rapakivi Batholith, Southwestern Finland

Paleostress inversion analysis of outcrop data from brittle fault structures within the Mesoproterozoic 1.58 Ga Åland rapakivi granite, southwestern Finland, revealed two separate strike-slip faulting stages. Stage 1 is dominated by dextral slip along E–W-trending faults under WNW–ESE to NNW–SSE compression, whereas Stage 2 displays less prominent faulting localized in an orthogonal network of N–S and E–W trending faults that developed under NE–SW compression. Relative age constraints indicate that faulting occurred between 1.58 and 0.5 Ga, and further correlation with previously published results indicate a 1.55–1.4 Ga age for Stage 1 faulting, while Stage 2 is compatible with previously described fault reactivations between 1.3–1.2 Ga. To place the results of the fault analyses in a wider framework, we conducted a regional structural interpretation using bathymetric, topographic, and geophysical datasets and reviewed previously published results. Based on the above, we attribute the emplacement of the 1.6–1.5 Ga rapakivi granites and the subsequent development of the Mesoproterozoic sedimentary basins to the reactivation of inherited Paleoproterozoic shear zones during Mesoproterozoic crustal extension. As such, this study contributes towards understanding the relationships between magmatism and strain localisation in continental (failed) rift settings.

Ichnological analysis and paleoenvironmental inferences of Neogene meandering fluvial deposits in Continental Rift of Southeastern Brazil

Ichnological analysis and paleoenvironmental inferences of Neogene meandering fluvial deposits in Continental Rift of Southeastern Brazil

Научная школа «Кайнозойский континентальный рифтогенез»: от основания к развитию (к 95-летию со дня рождения академика Н.А. Логачева)

The article, prepared in connection with the 95th anniversary of N.A. Logatchev's birth, highlights his role in the development of N.A. Florensov's ideas about Cenozoic continental rifting in the Baikal area. The author's vision of his path as a scientist is given, having established himself in his youth and uniting specialists of various profiles in his mature age into a new scientific direction "Cenozoic Continental Rifting", within the framework of which systematic knowledge about the Baikal and other Cenozoic continental rift systems was obtained.

Мониторинг окислительно-восстановительного потенциала подземных вод в режиме реального времени на Култукском полигоне в конце 2023 – начале 2024 г.: сопоставление электрических эффектов с землетрясениями в центральной части Байкальской рифтовой системы

The results of real-time observations of the oxidation-reduction potential (ORP) in groundwater from two wells in the Kultuk area from December 2023 to March 2024 are presented. Variations of this parameter show reorganizations, accompanied by short episodes of single earthquakes and longer intervals of earthquake series in the central part of the Baikal Rift System. A change from low to high ORP values accompanies the general transition from strong to weak earthquakes. The uneven variations in ORP of the monitoring stations are suggested to associate with piezoelectric effects that arise when seismic waves act on quartz of the ordered tectonite structures in different active structures of the South Baikal basin: in its marginal Obruchev fault and in the axial Kultuk tectonic step.