Mexico’s 2017 earthquake emerged from a growing risk zone

Under Mexico, where the Cocos Plate from the Pacific Ocean slides under the North American Plate, a bending line of hills, created when the seafloor first formed, sits atop a flattened area of subduction. That newly recognized combination has created a fault that likely explains last September’s Puebla earthquake, scientists report in a new study.

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Geochemistry and 40Ar/39Ar geochronology of the Nandurbar-Dhule mafic dyke swarm: Dyke-sill-flow correlations and stratigraphic development across the Deccan flood basalt province

The ENE-WSW-trending Nandurbar-Dhule swarm is the best developed tholeiitic dyke swarm in the Deccan Traps. We obtained 40Ar/39Ar ages of 67.06 ± 0.60, 67.49 ± 0.89, and 63.43 ± 0.48 Ma (2σ internal errors) on three of its largest dykes (36–79 km long), indicating that swarm emplacement spanned ≥2.5 million years under regional crustal extension. Our Sr-Nd-Pb isotopic data, combined with previously available geochemical data, identify multiple magma injections in some dykes and also identify probable feeder dykes of some lavas in the lower Western Ghats sequence and in Saurashtra, each ~200 km away. Several dykes are compositionally distinct from hitherto analysed lavas; >50% of the analysed Nandurbar-Dhule dykes are isotopically like the Mahabaleshwar and Panhala formations of the upper Western Ghats sequence, covering a very narrow isotopic range, but have the distinctive chemical signatures of the high-TiO2 Kolhapur Unit of the southernmost Western Ghats. These dykes thus possess a unique combination of isotopic and chemical characteristics not hitherto known in Deccan tholeiites, cross-combining features of different eruptive units in the Wai Subgroup of the Western Ghats. This new, “Nandurbar-type” chemical-isotopic flavour is however frequently observed in dykes, sills, and lavas in the Pachmarhi, Shahdol, and Mandla areas 450–600 km to the east, and in Deccan-age dykes cutting through the Early Cretaceous Rajmahal Traps of eastern India. Varied geochemical evidence indicates that the northern and northeastern Deccan lava stratigraphy (such as the Pavagadh section and the Pachmarhi-Shahdol-Jabalpur-Mandla areas) is largely independent of the Western Ghats lava stratigraphy.

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Ice-age echoes affect present-day sea level

A new study has, for the first time, cut a clear path through a nettlesome problem: accurately measuring a powerful effect on global sea level that lingers from the last ice age. Just how quickly Earth’s deep, rocky mantle is rebounding from the heavy burden of ancient ice sheets and oceans remains somewhat uncertain. But this rebound effect, known as glacial isostatic adjustment (GIA), is critical to properly understanding the causes of sea level change.

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Geochemistry and zircon U–Pb ages of basic rocks in the Kekebieketi mining area from Fuyun (Xinjiang, China) and their geological significance

The Kekebieketi mining area is located on the southern margin of the Altai Mountains in Northern Xinjiang and is at the junction of the Siberia and Kazakhstan-Junggar plates. Faults and magmatic rocks are well developed, and the main stratum is the Middle Devonian Kaxiweng Formation. The Kekebieketi-Kalatongke-Xibodu basic to ultrabasic mixed rock strip is an appropriate area for mineral resources and a good target to study the crustal and mantle evolution. This study explored the tectonic age and setting of basic rocks in the Kekebieketi mining area and provides a basis for the study of basic rocks and discrimination of the wider formation. The basic rocks were mainly gabbro, pyroxenolite, basic subvolcano rock, and diabase. They have all been altered to different degrees through amphibolization, sub-amphibolization, actinolitization, chloritization, epidotization, zoisitization, uralitization, and serpentinization. Similar rare earth element compositions of the different rock types suggest that they are homologous. Enrichment of large ion lithophile elements (Cs, Rb, Sr, and U) and depletion of high field strength elements (Nb, Ta, Zr, and Hf) showed that the basic rocks have the characteristics of island arc magmatic rocks. A single zircon U–Pb age of 321 ± 2.5 Ma was obtained from a hornblende gabbro. Based on the petrological and geochemical features, we concluded that the basic rocks in the study area were formed during the post-collision period in East Junggar. The parental magma is mainly composed of metasomatic mantle wedge material and upwelling asthenosphere, which is why it showed geochemical characteristics of subduction.

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Sr–Nd isotopes of Early and Late Carboniferous volcanic rocks in Yining Massif (Xinjiang, NW China): Implications for petrogenesis and tectonic evolution of Western Tianshan

The Yining Massif, sandwiched between the Junggar and Tarim plates, has received much attention because of its special position and complex tectonic evolution, as well as a significant breakthrough in geological prospecting. Moreover, a lot of studies have focused on two suites of volcanic rocks of the Early Carboniferous Dahalajunshan and Late Carboniferous Yishijilike formations in the Yining Massif. Recently, an increasing number of results have shown that two suites of volcanic rocks have obvious differences in lithochemistry and geochemistry and might have formed in an arc and intracontinental rift settings, respectively. Furthermore, the latest results of Sr–Nd isotopes indicate that the initial (87Sr/86Sr)i ratio is less than 0.7119 for all samples in the two formations. But the (87Sr/86Sr)i of andesites in the Dahalajunshan Formation is obviously higher than that of the Yishijilike Formation. However, those of dacites and rhyolites are just the opposite. The (143Nd/144Nd)i of all kinds of rocks from the Dahalajunshan Formation is less than 0.5126, and that of basalts in Yishijilike Formation is also less than 0.5126. However, the results of the andesites and rhyolites are higher than 0.5126. In short, the parameters of (87Sr/86Sr)i, (143Nd/144Nd)i, εNd(t), TDM (Ga), and εSr(t) are different obviously between the two suites, showing progressive change from basic to acid rocks in the two formations (gradual increase and decrease), but the changed direction is just the opposite. Consequently, it illustrates that there is a significant distinction in composition and petrogenesis between the Dahalajunshan and Yishijilike formations. The Dahalajunshan Formation volcanic rocks might be derived from an enriched mantle, whereas the volcanic rocks in the Yishijilike Formation are related to the evolution of continental crust. In other words, the differentiation of Sr–Nd isotopes provides a reference information for studying the petrogenesis and tectonic setting of the two suites of volcanic rocks.

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Hybodont dentition from the Upper Jurassic of Monte Nerone Pelagic Carbonate Platform (Umbria-Marche Apennine, Italy) and its ecological implications

Here we describe a number of articulated teeth of a hybodont shark from Upper Jurassic deposits of the Monte Nerone Pelagic Carbonate Platform, in the Umbria-Marche-Sabina Palaeogeographic Domain (Northern Apennines, Central Italy). The material has been referred to as Asteracanthus cf. A. magnus, a quite well-known taxon already reported from Middle to Upper Jurassic deposits of Europe. Teeth indicate an extreme crushing feeding behaviour, suggesting as putative prey both infaunal and epifaunal hard-shelled invertebrates dwelling the sea-floor, such as large bivalves, brachiopods, gastropods as well as vagile crustaceans. The finding represents, to date, the first formal report of hybodont shark in the Umbria-Marche-Sabina Domain, throwing further light on the ecology within Pelagic Carbonate Platform settings, and on the occurrence of Asteracanthus in the Late Jurassic of the Western Tethys.

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EWASS 2018: RAS grants for carers

The RAS is offering a carers’ grant scheme for the 2018 European Week of Astronomy and Space Science (EWASS 2018), to give eligible delegates a grant towards additional costs of paying for care when attending the conference.


Applications must be submitted by Monday 19 March 2018, and confirmation of eligibility will be given within one week of this deadline. Payment will be made on completion of a short form following attendance at the event. Retrospective awards will not normally be considered, and funds are limited, so we will prioritise those on lower incomes, for example students or delegates retired from employment.


The grant is available both for childcare, and for other caring responsibilities. It is a requirement of the grant for those applying to provide proof of the cost of care, for example a receipt for nursery payments incurred, or a letter from the Department of Work and Pensions (for UK applicants) proving that they are in possession of Carer’s Allowance.


Please apply using the following pdfgrant application form.


For more information please contact


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Triassic alkaline magmatism and mineralization in the Xiong’ershan area, East Qinling, China

The Qinling orogenic belt is a complex subduction–accretion–collision orogen that welded the North China Craton and the Yangtze Craton during the final continental collision in the Triassic. The Xiong’ershan area, located in east Qinling, exposes a typical Triassic syenite pluton and several contemporaneous Mo, Au, and Cu deposits. The aegirine–augite syenites and syenites from the Mogou pluton are characterized by alkalic to peralkalic (total alkali Na2O + K2O = 13.95–14.63 wt.%, CaO = 0.06–2.87 wt.%), and shoshonitic features (K2O = 11.86–14.34 wt.%). Zircon LA–ICP–MS U–Pb dating of the aegirine–augite syenite and syenite yield emplacement ages of 232.5 ± 0.6 and 221.8 ± 0.7 Ma, indicating multiple pulses of magmatism. Evidence from zircon Hf isotopes; occurrence of mafic microgranular enclaves; heterogeneous peralkaline composition; and wide ranges of MgO, Ni, and other trace elements suggest that the parental magma was mainly sourced from partial melting of Archean to Paleoproterozoic crustal sources, mixed with juvenile mantle-derived mafic magmas. The Mogou pluton was probably emplaced in the tectonic transition from syn-collision to post-collision settings and accompanying slab break-off process, from the commencement of collision at approximately 245 Ma and post-collisional extension at approximately 210 Ma. Gold, molybdenum, and copper deposits formed during the interval of 255–208 Ma, and the close temporal and spatial relationship between these Triassic polymetallic deposits and the Mogou alkaline pluton invokes a genetic linkage. The heat source for magmatism and related metallogeny is correlated to a hot upwelling asthenospheric mantle that caused partial melting of the Archean to Paleoproterozoic crustal basement, resulting in magma mixing between the two end-members.

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Petrogenesis of two stages of Cretaceous granites in south-west Fujian Province: Implications for the tectonic transition of South-east China

Zircon U–Pb data indicate that Cretaceous magmatism in Fujian Province occurred in two pulses, with the Xiyang, Yangshan, Wuci, Dehua, Juzhou, and Xiandu plutons emplaced between 147 ± 1 and 126 ± 1 Ma and the Hutou and Guangqiao plutons emplaced at 109 ± 1 Ma. Combining these previously published ages with the new data obtained during this study indicates that the magmatism in the study area occurred in two distinct stages at 145–125 and 110–100 Ma, both have I-type characteristics. The earlier I-type granites are characterized by relatively high concentrations of SiO2 (mean = 75.73 wt.%) and low concentrations of MgO (mean of 0.21 wt.%) and are metaluminous to weakly peraluminous (mean A/CNK = 1.03). They contain relatively high total rare-earth element (ΣREE) concentrations (mean of 139.3 ppm) with well-developed Eu anomalies and are relatively enriched in the large-ion lithophile elements (LILE) and the light REE (LREE) but depleted in Ba, Sr, P, Ti, Nb, and Ta. In contrast, the younger I-type granites contain lower concentrations of SiO2 (mean of 67.63 wt.%), higher concentrations of MgO (mean of 1.47 wt.%), and are metaluminous to weakly peraluminous (mean A/CNK = 0.96). They also have moderate REE values (mean of 150.26 ppm) without significant Eu anomalies and are relatively enriched in LREE, Rb, Th, U, K, Sr, and Pb and depleted in Nb, Ta, P, Ti, Y, and Yb. The two-stage Nd model ages (T2DM) of Cretaceous granites are 1.46 to 1.88 Ga (mean of 1.57 Ga) and 1.16–1.60 Ga (mean of 1.36 Ga), respectively. The two-stage Hf model ages (T2DM) of Cretaceous granites are 1.19–1.82 Ga (mean of 1.54 Ga) and 0.46–1.20 Ga (mean of 0.91 Ga), respectively. It is likely that the earlier I-type granites were derived from magmas generated by the partial melting of Mesoproterozoic metabasaltic material, whereas the later I-type granites were derived from magmas generated by partial melting of a mixed lithology containing Mesoproterozoic to Neoproterozoic metabasaltic to metatonalitic rocks that were underplated by medium- to high-K basaltic magmas. A geological comparison between south-western Fujian Province and adjacent areas indicates that the earlier I-type granites were emplaced in a compressional environment associated with the subduction of the paleo-Pacific Plate at 145–125 Ma. In contrast, the later I-type plutons are associated with intraplate extension accompanied by the post-subduction slab roll-back of the paleo-Pacific Plate. The two magmatic stages represent a transition from compressional to intraplate extensional tectonics between 125 and 110 Ma, with mantle-derived material playing a crucial role in the formation of the I-type granites.

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