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We report detrital zircon ages from the Upper Cretaceous (Campanian–Maastrichtian) turbiditic sandstones from the Pontides and the Anatolide–Tauride Block, which were located on opposite margins of the Tethys ocean during most of the Paleozoic and Mesozoic. The large data set includes both published and new detrital zircon ages from the Upper Cretaceous Pontide sandstones (2730 zircon ages from 26 samples) and new detrital zircon ages from the uppermost Cretaceous Bornova Flysch of the Anatolide–Tauride Block (378 ages from five samples). Phanerozoic detrital zircons from the Upper Cretaceous sandstones of the Pontides are predominantly Late Cretaceous (56%) followed by Carboniferous (7.9%), Devonian (5.3%), Jurassic (3.1%) and Triassic (2.9%). In contrast, there are no Cretaceous and Jurassic detrital zircons in the uppermost Cretaceous Bornova Flysch, and the Phanerozoic detrital zircon populations are mainly Carboniferous (41.3%), Triassic (7.1%), Permian (6.9%) and Devonian (5.3%). The absence of Cretaceous and Jurassic zircons in the Bornova Flysch shows that there was no sediment transport between the Pontides and the Anatolide–Tauride Block during the latest Cretaceous (75–70 Ma); it also shows that the latest Cretaceous – Paleocene deformation of the Bornova Flysch Zone predates the collision between the Pontides and the Anatolide–Tauride Block, and is associated with ophiolite obduction. The dominance of Carboniferous detrital zircons in the Bornova Flysch Zone underlines that Carboniferous magmatic activity in the Anatolide–Tauride Block, and hence on the northern margin of Gondwana, was more significant than hitherto recognized.

Flysch formations are widespread all around the Mediterranean basin and in many other parts of the world. Their special fabric, characterized by a strong heterogeneity due to alternations of often deformed lapideous and fine-grained layers and by a network of discontinuities, brings to light the strong limitations of the geo-engineering sciences when dealing with such complex materials. Based on the results of an investigation carried out in a long section of the Southern Apennines, the paper examines this problem focusing in particular on the role played by material fabric at different scales on the hydraulic and mechanical behavior of the deposit.HighlightsThe mechanical behaviour of the Red Flysch formation is carefully analysed with a particular attention to the influence of the soil fabric at different scales.The Red Flysch formation is described within the frame of the structurally complex formationsThe results of a wide in situ and laboratory investigation on a Red Fysch deposit are collected and interpretedThe role played by material fabric at different scales on the hydraulic and mechanical behavior of the deposit is evidenced.The strong limitations of the geo-engineering sciences when dealing with such complex materials are highlighted

Field investigations and back-analyses of (re)activated landslides in the Rječina River Valley indicate prolonged intense rainfall and the rise of the groundwater table, often to the slope surface, which are common prerequisites for the occurrence of landslides in the valley. However, previous studies have never considered the transient process of rainfall infiltration in the unsaturated zone of the slope, quantified the infiltrated volumes, or determined its effect on the stability of a slope over time. This study presents a numerical model capable of determining the transient pore-water pressure distributions on a flysch slope subjected to a realistic rainfall event and how rainfall affects the stability condition over time. This investigation presents a case study of the Valići Landslide that was reactivated on 13 February 2014 after several months of intense, mostly uninterrupted rainfall. Under certain constraints and working assumptions, 10-min rainfall data collected at the site are used to study the hydraulic response of the slope during 167 days of the simulation, as well as the changes in the slope that led to the reactivation event. The results obtained quantitatively confirm rainfall duration to be a crucial factor in landslide reactivation. On the other hand, an analysis performed using synthetic rainfall data suggests that the time required to reach failure remained unaffected for rainfall intensities greater than 8 mm/day. This study suggests that the unsaturated zone plays a crucial role in maintaining the stability of a slope during prolonged rainfall, with a strong correlation between the antecedent rainfall and time to failure.

Myanmar is occupied by the N-wards continuation of the Sunda arc and by the Shan Plateau and its continuation through Yunnan into Tibet. Our new tectonic interpretation of the ophiolite–flysch belts, world-famous jadeite and tin deposits in Myanmar west of the Salween adopts previous proposals that, before 450-km post-early Oligocene dextral displacement along the Sagaing Fault, the ophiolite belt in NE Myanmar continued through the topography that is now located west of the fault in the Indo-Burman Ranges. Differences in cross-section through Mogok and the Shan Scarps are reconciled by the recently proposed emplacement, in our view during Permian time, of the Mogok Metamorphic Group onto the Slate Belt to form Sibumasu. We argue that during Early Jurassic time a Neo-Tethys ophiolite nappe was obducted over turbidites on Sibumasu’s passive western margin. Following reversal in tectonic polarity, the remaining Neo-Tethys subducted E-wards generating the 113–128 Ma Mondaung Arc. During ocean closure the Victoria–Katha Block and its Triassic flysch subducted beneath Sibumasu, resulting in jadeite veins in overlying serpentinite that ascended in the subduction zone and were exhumed at Hpakant and Nat Hmaw, bordering the Jade Mines Uplift. Subduction of the Indian Ocean since Albian time generated the Popa–Loimye arc, while extensional faulting led to uplift of the Indo-Burman Ranges and to the formation of the Western Tin Belt granites. Tectonic effects in Myanmar of the India–Asia collision may be confined to the Disang thrust belt in the Naga Hills.

Twenty-one sandstone samples belonging to the intermediate part of Gorgoglione Flysch (GF) dated Middle-Miocene, cropping out in the Southern Apennines (Italy), have been studied to highlight the detritus provenance. Petrographic and chemical composition indicates that the successions consist of feldspatho-quartzose and litho-feldspatho-quartzose arenites interbedded with pelitic and calciclastic layers and reveals a provenance from a basement formed by low- to medium-grade metamorphic rocks with abundant granitoids covered by sedimentary rocks in which a volcanic component was also present. In the Mediterranean area, basements with these characteristics are widespread both in western and southwestern domains. The supply provenance of Gorgoglione Flysch has been better detailed utilizing U–Pb detrital zircon ages recording the geological history of the source rocks. Fifty-eight crystals from six samples of coarse- and fine-grained sandstones have been analysed using the U–Pb isotopic systematic (LA-ICP-MS). They produce 70 concordant zircon ages forming three defined clusters at 672 ± 28 Ma, 458 ± 9 Ma and 297 ± 8 Ma, and four zircon ages corresponding to 24 ± 1 Ma. An evaluation of the entire collected data suggests that the provenance area is better identified in northwestern sectors of the Mediterranean area in which the Sardinia–Corsica (pro-part) block plays a fundamental role.

Radiogenic strontium isotopes (87Sr/86Sr) of vein carbonates play a central role in the tectonometamorphic study of fold-and-thrust belts and accretionary wedges and have been used to document fluid sources and fluxes, for example, along major fault zones. In addition, the 87Sr/86Sr ratios of vein carbonates can trace the diagenetic to metamorphic evolution of pore fluids in accreted sediments. Here we present 87Sr/86Sr ratios of vein carbonates from the Infrahelvetic flysch units of the central European Alps (Glarus Alps, Switzerland), which were accreted to the North Alpine fold-and-thrust belt during the early stages of continental collision. We show that the vein carbonates trace the Sr isotopic evolution of pore fluids from an initial seawater-like signature towards the Sr isotopic composition of the host rock with increasing metamorphic grade. This relationship reflects the progressive equilibration of the pore fluid with the host rock and allows us to constrain the diagenetic to low-grade metamorphic conditions of deformation events, including bedding-parallel shearing, imbricate thrusting, folding, cleavage development, tectonic mélange formation and extension. The strontium isotope systematics of vein carbonates provides new insights into the prograde to early retrograde tectonic evolution of the Alpine fold-and-thrust belt and helps to understand the relative timing of deformation events.

When and how the Bangong–Nujiang Tethyan Ocean closed is a highly controversial subject. In this paper, we present a detailed study and review of the Cretaceous ophiolites, ocean islands, and flysch deposits in the middle and western segments of the Bangong–Nujiang suture zone (BNSZ), and the Cretaceous volcanic rocks, late Mesozoic sediments, and unconformities within the BNSZ and surrounding areas. Our aim was to reconstruct the spatial–temporal patterns of the closing of the middle and western segments of the Bangong–Nujiang Tethyan Ocean. Our conclusion is that the closure of the ocean started during the Late Jurassic and was mainly complete by the end of the Early Cretaceous. The closure of the ocean involved both “longitudinal diachronous closure” from north to south and “transverse diachronous closure” from east to west. The spatial–temporal patterns of the closure process can be summarized as follows: the development of the Bangong–Nujiang Tethyan oceanic lithosphere and its subduction started before the Late Jurassic; after the Late Jurassic, the ocean began to close because of the compressional regime surrounding the BNSZ; along the northern margin of the Bangong–Nujiang Tethyan Ocean, collisions involving the arcs, back-arc basins, and marginal basins of a multi-arc basin system first took place during the Late Jurassic–early Early Cretaceous, resulting in regional uplift and the regional unconformity along the northern margin of the ocean and in the Southern Qiangtang Terrane on the northern side of the ocean. However, the closure of the Bangong–Nujiang Tethyan Ocean cannot be attributed to these arc–arc and arc–continent collisions, because subduction and the development of the Bangong–Nujiang Tethyan oceanic lithosphere continued until the late Early Cretaceous. The gradual closure of the middle and western segments of Bangong–Nujiang Tethyan Ocean was diachronous from east to west, starting in the east in the middle Early Cretaceous, and being mainly complete by the end of the Early Cretaceous. The BNSZ and its surrounding areas underwent orogenic uplift during the Late Cretaceous.

Within the upper Paleocene (Thanetian) flysch conglomeratic sandstones of the Magura Nappe, a bed characterized by dominant coralline red algae, with subordinate benthic foraminifera, corals, bryozoans, and molluscs has been identified. It is the only known site showing evidence of rarely explored Paleocene shallow-water areas in the Magura Basin. Corallines occur as abraded coralline algal debris and rhodoliths. The upper Paleocene coralline algal debris consists of rounded, sand- to pebble-size clasts. Two types of rhodoliths were distinguished: abraded sub-spheroidal boxwork up to 0.5 cm in diameter, and irregular boxwork rhodoliths larger than 1 cm in diameter. In the coralline algal assemblage, the most abundant component is Sporolithon sp., with subordinate Lithothamnion sp. and Mesophyllum sp. Karpathia sphaerocellulosa and Spongites sp. are also present. Bioerosions, such as Entobia isp., Gastrochaenolites isp., Trypanites isp., and microborings are common in the coralline debris. This assemblage documents the shallow-water carbonate biogenic sedimentation in the northern Magura Basin during the Thanetian. These corallines formed above the storm wave base and were redeposited offshore in the inner part of the Magura Basin by sediment gravity flows.

This paper reports the results of a field-based structural investigation of a well-exposed paleo-accretionary prism, which experienced complex deformation in a low-grade metamorphic setting. Field analyses focused on the description of structural fabrics, with the main emphasis upon parameters like the orientation, style and kinematics of foliations, folds and shear zones. We address the research to the south-westernmost part of the Alpine chain, the Ligurian Alps, where, despite their origin as turbidite sequences deposited into the closing Alpine Tethys Ocean, the Helminthoid Flysch Nappes are presently distributed in the outer part of the chain, above the foreland. The new dataset highlights different deformation patterns related to the different spatial distribution of the flysch units. This regional-scale partitioning of strain is hence associated with progressive deformation within a two-stage geodynamic evolution. Correlations among the different orogenic domains allow the proposal of a kinematic model that describes the motion of the Helminthoid Flysch from the inner to the outer part of the orogen, encompassing the shift from subduction- to collision-related Alpine geodynamic phases.

The key magmatic processes that lead to the formation of large magmatic-hydrothermal porphyry copper mineral deposits remain uncertain, and a particular question is why a few of these deposits, such as the Pebble porphyry Cu-Au-Mo deposit, are strongly enriched in both gold and molybdenum. This study investigated the igneous rocks of the Pebble district and obtained major and trace element compositions, Sr and Nd isotopic compositions, and zircon age and trace element data to model the origin of the ore-forming magmas.The Pebble porphyry Cu-Au-Mo deposit, one of the world's largest Cu-Au resources, formed during the final stages of regional Late Cretaceous arc magmatism (101-88 Ma) in the Southwest Alaska Range. Local pre-mineral intrusions (99-95 Ma) are dominated by alkaline compositions including monzodiorite stocks, shoshonite dikes, and monzonite porphyries, but also include lesser volumes of high-K calc-alkaline diorite and granodiorite sills. The occurrence of early alkaline magmas has been noted at other gold-rich porphyry systems, including Bingham and Kerr-Sulfurets-Mitchell. Mineralization at Pebble is associated with granodiorite to granite porphyry dikes related to the >165 km2 high-K calc-alkaline Kaskanak granodiorite batholith (91-89 Ma). Over a period of 10 m.y., Late Cretaceous melts evolved from high temperatures (930-730 °C) and modestly hydrous and oxidized conditions to relatively low temperatures (760-680 °C) and very hydrous and oxidized conditions. Collectively, all Late Cretaceous igneous rocks at Pebble contain magnetite and little or no ilmenite, are metaluminous to weakly peraluminous, and have typical arc trace element enrichments and depletions. They have moderate Sr/Y ratios (20-55) and gently sloped REE profiles (La/Yb = 5-20) that are not adakitic, which supports a source area lacking garnet that is consistent with a thin crust in southwest Alaska. Radiogenic isotopes for Late Cretaceous intrusions at Pebble have a restricted range of primitive Sr and Nd isotopic compositions (87Sr/86Sri = 0.70329-0.70424; εNdi = 4.9-6.1), which overlap with volcanic and plutonic basement rocks of the Jurassic Talkeetna Arc along the Alaska Peninsula. The Kaskanak batholith intrudes the Late Jurassic-Early Cretaceous Kahiltna flysch, and mixing models using Sr and Nd isotopes indicate that the Kaskanak batholith assimilated ≤10 wt% Kahiltna flysch in amounts that did not likely affect magma fertility. Xenocrystic zircon samples are abundant in Cretaceous pre-mineral intrusions and have U-Pb ages similar to detrital zircon samples in the Kahiltna flysch. These data support some assimilation of upper crustal Kahiltna flysch, but the dominance of Devonian-Mississippian xenocrystic zircon populations in some intrusions suggests derivation from unexposed older basement. The extraordinary endowment of Cu and Au at Pebble is inferred to result from primitive calc-alkaline and alkaline arc magmas and the hydrous and strongly oxidized conditions that suppressed the formation and fractionation of Cu- and Au-enriched sulfide melts. Furthermore, differentiation to silicic compositions was a product of extensive crystal fractionation of parental melts accompanied by minor crustal assimilation. The trace element content of the intermediate composition intrusions indicates that both hornblende and titanite fractionation processes in the mid- to shallow-crust were both required to produce the more evolved granodiorite and granite porphyry compositions. Despite the apparent lack of Mo-enriched continental crust in the region, primitive hydrous melts were produced by protracted arc magmatism and were modified by minor crustal assimilation including early alkaline magmatism, periodic recharge of mafic hydrous basalts and hybrid andesites, and fractional crystallization, which was apparently sufficient to enrich Mo in late stage felsic melts.