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We investigated highly mature sedimentary rocks exposed along both sides of the Fram Strait in the northern North Atlantic using apatite fission track and (U-Th)/He thermochronology to obtain information on the thermal imprint of rifting and continental breakup processes along a sheared margin. Our data showed that the conjugate margins experienced several heating episodes, which we explain as resulting from heat transfer along segments of the De Geer Fracture Zone, a large continental transform system which connected magmatic centers north and south of the Fram Strait. Heating occurred prior to and during the Eurekan intraplate orogeny, which occupied the position of the present-day Fram Strait during the Eocene. Heat transfer may have caused or contributed to lithospheric weak zones, which focussed deformation during intraplate orogeny. Movements along the transform fault system continued during the Oligocene, after the end of the Eurekan Orogeny, causing further structural weakening of pre-existing fault zones. These were exploited during the final continental breakup leading to the opening of the Fram Strait. No unambiguous thermal signature associated with this latest stage of breakup was detected. Our data underline recent studies on the importance of structural inheritance and continental transform faults for the prolonged and complex processes of continental rifting and breakup.

An old large-scale landslide with a volume of 4.6 × 106 m3 located on the right bank of the Lancang River, Southwest China, was formed by the deep-seated toppling failure of a rock mass. The rock mass located downstream of the landslide toppled intensely with a maximum toppling depth exceeding 200 m and a volume over 1.5 × 108 m3. We studied the formation mechanism of the landslide and determined the most likely future instability range of the toppled rock mass. The results show that the toppled rock mass located downstream of the landslide could be classified into four zones, namely, highly toppled, moderately toppled, weakly toppled and normal rock mass, from the surface to the deep-seated rock mass along the slope according to three factors: the unloading intensity, variation in the occurrence of the rock layer, and toppling fracture zone. The bottom boundary of the highly toppled rock mass was limited by the depth of strong unloading of the rock mass. The landslide deposits mainly originated from the highly toppled rock mass, and the slip zone was formed based on the toppling fracture zones. The highly toppled rock mass in the rock slope located downstream of the landslide will be the most likely area of instability in the future.

The failure characteristics of roof strata in coal mining and the accurate prediction of mine water inflow are prerequisites for mine safety. Taking a typical coal mine in Southwest China as a case, a new type of similar material suitable for coal mine in exposed karst areas was developed. Through the physical and numerical simulation, the failure characteristics of overlaying rock in karst areas were analyzed. The results showed that the plastic zone developed and accumulated from the roof. After mining, the stress and displacement of overlying rock were divided into three areas along the mining direction. The middle area experienced the maximum change. Overall, the height of falling and water-conducting fracture zones in karst exposed areas was slightly lower than that in other areas. And then, the hydrogeological structure considering the water-conducting fracture zone was rationally generalized, and a three-dimensional numerical model for predicting mine water inflow was built. It was found that the numerical simulation method had the minimum error and the maximum accuracy than other traditional methods, and its results were the closest to the measured value, which could more truly reflect the dynamic formation process of mine water inflow. Graphical Abstract

The mineralogy of manganese nodules from the German license area in the eastern Clarion and Clipperton Zone (CCZ) of the central Pacific Ocean was studied using X-ray diffraction. Their individual nanometer to micrometer thick genetically different (hydrogenetic/diagenetic) layer growth structures were investigated using high-resolution transmission electron microscopy. Relationships between the mineral phases and metal content (e.g., Ni+Cu) were assessed with electron microprobe analyzer. The main manganese phase detected in nodules of this study was vernadite, a nanocrystalline and turbostratic phyllomanganate with hexagonal layer symmetry. In layer growth structures of hydrogenetic origin, Fe-vernadite dominates. Layer growth structures of suboxic-diagenetic origin contain three vernadite forms, which are the main Ni and Cu carriers. These Mn-phases were identified on the basis of their structural layer-to-layer distances (7 and 10 Å) and on their capacity to retain these distances when heated. The first form is 7 Å vernadite, which is minor component of the nodules. The second is a thermally unstable ∼10 Å vernadite collapsing between room temperature and 100°C, and the third is a thermally stable ∼10 Å vernadite collapsing between 100 and 300°C. Todorokite was neither detected in bulk nodules nor in any of the individual suboxic-diagenetic growth structures. Because the mineralogical composition of the nodule is quite homogeneous (only different vernadite-types), it is suggested that the content of Ni and Cu in the individual growth structures is controlled by their availability in the environment during individual growth phases. A profile through a CCZ nodule revealed that the thermal stability of the vernadites change from younger (thermally unstable vernadites, collapsing <100°C) to older growth structures (thermally stable 10 Å vernadites, collapsing >100°C) of the nodule accompanied with changes in type and amount of interlayer cations (e.g., Mg, Na, Ca, K). The stability of the vernadites is probably due to re-organization and incorporation of metals within the interlayer of the crystal structure.

In two companion papers, we report the detailed geological and mineralogical study of two emblematic serpentinized ultramafic bodies of the western North Pyrenean Zone (NPZ), the Urdach massif (this paper) and the Saraille massif (paper 2). The peridotites have been exhumed to lower crustal levels during the Cretaceous rifting period in the future NPZ. They are associated with Mesozoic pre-rift metamorphic sediments and small units of thinned Paleozoic basement that were deformed during the mantle exhumation event. Based on detailed geological cross-sections and microprobe mineralogical analyses, we describe the lithology of the two major extensional fault zones that accommodated: (i) the progressive exhumation of the lherzolites along the Cretaceous basin axis; (ii) the lateral extraction of the continental crust beneath the rift shoulders and; (iii) the decoupling of the pre-rift cover along the Upper Triassic (Keuper) evaporites and clays, allowing its gliding and conservation in the basin center. These two fault zones are the (lower) crust-mantle detachment and the (upper) cover decollement located respectively at the crust-mantle boundary and at the base of the detached pre-rift cover. The Urdach peridotites were exposed to the seafloor during the Late Albian and underwent local pervasive carbonation and crystallization of calcite in a network of orthogonal veins (ophicalcites). The carbonated serpentinized peridotites were partly covered by debris-flows carrying fragments of both the ultramafics and Paleozoic crustal rocks now forming the polymictic Urdach breccia. The mantle rocks are involved in a Pyrenean overturned fold together with thin units of crustal mylonites. Continent-derived and mantle-derived fluids that circulated along the Urdach crust-mantle detachment led to the crystallization of abundant metasomatic rocks containing quartz, calcite, Cr-rich chlorites, Cr-rich white micas and pyrite. Two samples of metasomatized material from the crust-mantle detachment yielded in situ zircon U/Pb ages of 112.9±1.6 Ma and 109.4±1.2 Ma, thus confirming the Late Albian age of the metasomatic event. The cover decollement is a 30-m thick fault zone which also includes metasomatic rocks of greenschist facies, such as serpentine-calcite association and listvenites, indicating large-scale fluid-rock interactions implying both ultramafic and continental material. The lowermost pre-rift cover is generally missing along the cover decollement due to tectonic disruption during mantle exhumation and continental crust elision. Locally, metasomatized and strongly tectonized Triassic remnants are found as witnesses of the sole at the base of the detached pre-rift cover. We also report the discovery of a spherulitic alkaline lava flow emplaced over the exhumed mantle. These data collectively allow to propose a reconstruction of the architecture and fluid-rock interaction history of the distal domain of the upper Cretaceous northern Iberia margin now inverted in the NPZ.

With more underground coal mining, soil subsidence and fracture have increasingly developed and resulted in changed hydrological progress; however, the effects of subsidence fracture on plant water uptake patterns remain largely unknown. This study aimed at investigating whether there were variations in soil water transport and plant water use patterns in subsidence fracture zone and fracture-free zone compared to the non-mining areas. The isotopically labeled water (2H) injection experiments were conducted and the MixSIAR model was used to explore the mechanism of soil water infiltration and water sources of Artemisia Desertorum in a semi-arid coal-mining area. The results showed that: (1) the proportion of the preferential flow in the subsidence fracture zone from the water balance equation was 18.2%; (2) in non-mining zone, 59.7% of water used by Artemisia Desertorum was from the 10–20 cm soil profile layer; (3) in the fracture-free zone, 46.6% and 39.4% of water were from the 40–60 cm and 0–10 cm layers, respectively; and (4) in the subsidence fracture zone, 85.9% of water derived mainly from the 40–60 cm layer. This study provided new insights into soil water transport and plant water uptake patterns in the subsidence fracture zone of coal-mining areas.

The hydrogeological conditions of the Qianbei coalfield are complex, and karst water in the roof rock frequently disrupts mining operations, leading to frequent water inrush incidents. Taking the representative Longfeng Coal Mine as a case study, research was conducted on the development pattern of the water-conducting fracture zone and the water inrush mechanisms beneath karst aquifers. On the basis of key stratum theory and calculations of the stratum stretching rate, the karst aquifer in the Changxing Formation was identified as the primary key stratum. It was deduced that the water-conducting fracture zone would develop into the karst aquifer, indicating a risk of roof water inrush at the working face. Numerical simulations were used to study the stress field, displacement field, and plastic zone distribution patterns in the overlying roof strata. Combined with similar simulation tests and digital speckle experiments, the spatiotemporal evolution characteristics of the water-conducting fracture zone were investigated. During the coal mining process, the water-conducting fracture zone will exhibit a \"step-type\" development characteristic, with the fracture morphology evolving from vertical to horizontal. Near the goaf boundary, the strain gradually decreases, and the instability of the primary key stratum significantly impacts the mining space below, leading to the closure of interlayer voids or the redistribution of water-conducting fissure patterns. Field measurements of the water-conducting fracture zone reveal that postmining roof fractures can be classified into tensile-shear, throughgoing, and discrete types, with decreasing water-conducting capacity in that order, the measured development height of the water-conducting fracture zone (51 m) aligns closely with the theoretical height (51.37 m) and the numerical simulation height (49.17 m). Finally, from the perspective of key stratum instability, the disaster mechanisms of dynamic water inrush and hydrostatic pressure water inrush beneath the karst aquifers in the northern Guizhou coalfield were revealed. The findings provide valuable insights for water prevention and control efforts in the Qianbei coalfield mining area.

To clarify water-conducting fracture zones (WCFZ) development under repeated mining, this study focuses on Huayang Coal Mine's Working Face 15101, adopting an integrated multi-method framework (experimental testing-visual verification-theoretical simulation). Borehole water injection tests are conducted to obtain the variation of WCFZ's permeability coefficient and its developmental height; by observing fracture morphology through borehole television, a quantitative correlation between “permeability coefficient and fracture structure” is established. The study also utilizes theoretical calculations and numerical simulations to predict WCFZ height evolution, and systematically reveals the development characteristics of WCFZ under repeated mining and the law governing its influence on the permeability of overlying strata. Results indicate that the permeability coefficients of the caving zone and fracture zone are 4.9–8.2 and 1.6–4.6 times those of the original rock strata, respectively. This pattern is supported by the fracture morphology observed through borehole television. Numerical simulations find that mining the No. 15 coal seam increases the No. 9 coal seam's overlying WCFZ height by approximately 11.4%. With the study comparing field measurements (75.31 m), theoretical analysis results (68.87 m, approximately 8.6% lower), and numerical simulations (73.87 m, approximately 1.9% lower), the final WCFZ height after repeated mining is determined by field measurements. These findings improve understanding of repeated mining-induced WCFZ and guide roof water hazard mitigation in similar mines.

Abyssal plains of the Clarion Clipperton Fracture Zone (CCZ) in the NE Pacific Ocean probably harbour one of the world’s most diverse ecosystems. Gaining a basic understanding of the mechanisms underlying the evolution and persistence of CCZ biodiversity in terms of biogeography and connectivity has both scientific merit and informs the development of policy related to potential future deep-sea mining of mineral resources at an early stage in the process. Existing archives of polychaetes and isopods were sorted using a combined molecular and morphological approach, which uses nucleotide sequences (cytochrome c oxidase subunit I (COI)) and morphological information to identify appropriate sample sets for further investigations. Basic patterns of genetic diversity, divergence and demographic history of five polychaete and five isopod species were investigated. Polychaete populations were found to be genetically diverse. Pronounced long- and short-distance dispersal produces large populations that are continuously distributed over large geographic scales. Although analyses of isopod species suggest the same, spatial genetic structuring of populations do imply weak barriers to gene flow. Mining-related, large-scale habitat destruction has the potential to impact the continuity of both isopod and polychaete populations as well as their long-term dispersal patterns, as ecosystem recovery after major impacts is predicted to occur slowly at evolutionary time scales.

The Red Sea provides an opportunity to study the processes during the transition from continental rifting to early-stage seafloor spreading during ocean initiation. We delineate variations of lithospheric architecture and the nature of extension along the Red Sea region through joint interpretation of gravity and geoid anomalies and gravity-topography transfer functions. We use lithospheric-scale models to compare stretching factors with upper mantle gravity anomaly, residual mantle Bouguer anomaly, and effective elastic thickness. Based on our observations, the Red Sea is divided into four segments; each having distinct lithospheric characteristics and stretching styles. These are: (i) southernmost Red Sea and Danakil having regionally weak and stretched lithosphere, (ii) southern Red Sea with fully developed seafloor spreading and asymmetric lithospheric architecture, (iii) central Red Sea having discontinuous magma accretion with newly formed seafloor spreading, and (iv) northern Red sea with a stronger lithosphere and limited stretching revealing a stage of continental rifting. In these segments, lithospheric stretching correlates with regions of weak lithosphere, including a regime of sublithospheric plume channel beneath the southern Red Sea. The Zabargad fracture zone between the central and northern segments is revealed as a major lithosphere-scale boundary that may act as a barrier to the propagation of seafloor spreading into the northern Red Sea. The weak and highly stretched lithosphere in this region may indicate the onset of a new spreading cell. Our results conclude that the evolution of the Red Sea is more complex than the previously suggested kinematic models of simple \"unzipping\" and illustrate that several extensional styles can exist within different segments during the initial stages of ocean formation.