New detrital zircon U-Pb ages and Lu-Hf isotopic data from metasedimentary rocks along the western boundary of the composite Avalon terrane in the southeastern New England Appalachians

ABSTRACT West Avalonia is a composite terrane that rifted from the supercontinent Gondwana in the Ordovician and accreted to Laurentia during the latest Silurian to Devonian Acadian orogeny. The nature and extent of West Avalonia are well constrained in Nova Scotia, New Brunswick, and Newfoundland, Canada, by U-Pb detrital zircon data and/ or isotope geochemistry of (meta)sedimentary and igneous rocks. The southeastern New England Avalon terrane in eastern Massachusetts, Connecticut, and Rhode Island has generally been interpreted as an along-strike continuance of West Avalonia in Canada, but the ages and origins of metasedimentary units along the western boundary of the Avalon terrane in Massachusetts and Connecticut remain poorly constrained. In this study, new detrital zircon U-Pb and Lu-Hf laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) data from three samples of metasedimentary units along the western boundary of the southeastern New England Avalon terrane in Connecticut and Massachusetts were compared with existing data to test whether these metasedimentary units can be correlated along strike. The data were also compared with existing detrital zircon U-Pb and εHf data in New England and Canada in order to constrain the extent and provenance of West Avalonia. The maximum depositional age of two of the three detrital zircon samples analyzed in this study, based on the youngest single grain in each sample (600 ± 28 Ma, n = 1; 617 ± 28 Ma, n = 1) and consistency with existing analyses elsewhere in the southeastern New England Avalon terrane, is Ediacaran, while that of the third sample is Tonian (959 ± 40 Ma, n = 4). Detrital zircon analyses of all three samples from this study showed similar substantial Mesoproterozoic and lesser Paleoproterozoic and Archean populations. Other existing detrital zircon U-Pb data from quartzites in the southeastern New England Avalon terrane show similar Tonian populations with or without Ediacaran grains or populations. Most published detrital zircon U-Pb data from (meta)sedimentary rocks in West Avalonia in Canada yielded Ediacaran youngest detrital zircon age populations, except for a quartzite unit within the Gamble Brook Formation in the Cobequid Highlands of Nova Scotia, which showed a Tonian maximum depositional age, and otherwise a nearly identical detrital zircon signature with rocks from the southeastern New England Avalon terrane. All samples compiled from the southeastern New England Avalon terrane and West Avalonia in Canada show main age populations between ca. 2.0 Ga and ca. 1.0 Ga, with major peaks at ca. 1.95, ca. 1.50, ca. 1.20, and ca. 1.00 Ga, and minor ca. 3.1–3.0 Ga and ca. 2.8–2.6 Ga populations. The εHf(t) values from the three samples yielded similar results to those from West Avalonia in Canada, suggesting that both regions were derived from the same cratonic sources. The εHf(t) values of all West Avalonian samples overlap with both Amazonia and Baltica, suggesting that there is a mixed signature between cratonic sources, possibly as a result of previous collision and transfer of basement fragments between these cratons during the formation of supercontinent Rodinia, or during subsequent arc collisions.

Petrogenesis of Dacites in a Triassic Volcanic Arc in the South China Sea: Constraints From Whole Rock and Mineral Geochemistry

Triassic volcanic rocks, including basalts and dacites, were drilled from Meiji Atoll in the South China Sea (SCS), which represents a rifted slice from the active continental margin along the Cathaysia Block. In this study, we present apatite and whole rock geochemistry of Meiji dacites to decipher their petrogenesis. Apatite geochronology yielded U-Pb ages of 204–221 Ma, which are identical to zircon U-Pb ages within uncertainty and thus corroborate the formation of the Meiji volcanic rocks during the Late Triassic. Whole rock major elements suggest that Meiji dacites mainly belong to the high-K calc-alkaline series. They display enriched patterns in light rare earth elements (LREE) and flat patterns in heavy rare earth elements (HREE). They show enrichment in large-ion lithophile elements (LILE) and negative anomalies in Eu, Sr, P, Nb, Ta, and Ti. The dacites have initial 87Sr/86Sr ratios of 0.7094–0.7113, εNd(t) values of -5.9–-5.4 and εHf(t) values of -2.9–-1.7, whereas the apatite has relatively higher initial 87Sr/86Sr ratios (0.71289–0.71968) and similar εNd(t) (-8.13–-4.56) values. The dacites have homogeneous Pb isotopes, with initial 206Pb/204Pb of 18.73–18.87, 207Pb/204Pb of 15.75–15.80, and 208Pb/204Pb of 38.97–39.17. Modeling results suggest that Meiji dacites can be generated by <40% partial melting of amphibolites containing ∼10% garnet. Therefore, we propose that the Meiji dacites were produced by partial melting of the lower continental crust beneath the South China block, triggered by the underplating of mafic magmas as a response to Paleo-Pacific (Panthalassa) subduction during the Triassic. Meiji Atoll, together with other microblocks in the SCS, were rifted from the South China block and drifted southward due to continental extension and the opening of the SCS.

Proposal of an Innovative Benchmark for the Evaluation of 3D Printing Accuracy for Photopolymers

In recent years, the diffusion of additive manufacturing (AM) or 3D printing (3DP) techniques for polymers have been boosted by the expiration of earlier patents from the last century and the development of low-cost machines. Since these technologies become more widespread, there is a need to assess the capability and accuracy of low-cost machines in terms of dimensional and geometric tolerance. To this aim, this work proposes an innovative reference part for benchmarking layerwise processes that involve the curing of photopolymers. The geometry of the part is conceived to include several classical shapes that are easily measurable for defining the part accuracy in terms of ISO IT grades and GD&T values. Two replicas of the reference part were fabricated by stereolithography (SLA) and digital light processing (DLP) using two machines and related proprietary materials by Sharebot Company. The replicas were printed with a layer thickness of 50 μm for the DLP process and 100 μm for the SLA one. The results of dimensional measurements of the replicas, that were carried out using a Coordinate Measuring Machine (CMM), show that the geometric accuracy of the time-consuming DLP process is slightly better than that of stereolithography.

Geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic composition of the Cha Val plutonic rocks in central Vietnam: Implications for Permian-Triassic Paleo-Tethys subduction-related magmatism

together with abundant Permian-Triassic magmatic rocks. This magmatic complex provides important information to reconstruct the tectonic evolution of the Indochina block and surrounding areas. The Cha Val plutonic rocks mainly comprise diorite, quartz diorite, and granodiorite. Geochemically, they are metaluminous with low A/CNK (0.49 to 1.16 with an average of 0.85), medium to high K, low to medium SiO2, and Na2O/K2O>1. Trace and rare earth element compositions display enrichment in Cs, U, Pb, and Nd, but depletion in Ba, Nb, Ta, P, Eu, and Ti, similar to those of continental arc-related magmas. Rock-forming minerals of the Cha Val plutonic rocks are characterized by abundant hornblende. All observed petrographical and geochemical characteristics suggest that the Cha Val plutonic rocks are typical for I-type affinity generated from a subduction regime. LA-ICP-MS U-Pb zircon analyses of three representative samples yielded their crystallization ages between 258.0 Ma and 248.9 Ma, temporally coeval with Late Permian-Early Triassic magmatism previously reported in the Truong Son belt. The (87Sr/86Sr)i ratios (0.7081 to 0.7244), negative whole-rock εNd(t) values (-4.5 to -2.9), zircon εHf(t) values (-1.04 to 2.71), and whole-rock Nd and zircon Hf model ages (TDM2) (1394 Ma to 1111 Ma) indicate that the Cha Val plutonic rocks are derived from melting of Mesoproterozoic crustal materials with a minor contribution of mantle-derived melt. Together with other Permian-Triassic magmatic complexes along the Song Ma suture zone and the Truong Son Belt, the Cha Val plutonic rocks are a representative of magmatism associated with the subduction-collision that amalgamated the South China and Indochina blocks after the closure of a branch of Paleo-Tethys along the Song Ma suture zone during the Late Permian-Early Triassic Indosinian orogeny.

Characterization of steel billet scales generated during the continuous casting process in SIDERPERU steel plant

Tons of waste is produced during iron steel’s industrial production, creating environmental pollution. This work aims to characterize the steel scale formed on the billet surface during the last step of steel production in the SIDERPERU steel plant. Scanning Electron Microscopy (SEM) shows stacked layers one above the other on steel billets scales surface. Energy Dispersive X-ray (EDX) and X-ray Fluorescence (XRF) reveal the high content of Fe and O, with Ca, Si, Mn, and Cr as minority elemental compounds. X-ray Diffraction (XRD) shows FeO, α-Fe2O3 and Fe3O4 as crystallographic phases. Magnetometry reveals Verwey transition and paramagnetic signals that screen the Morin transition. Mössbauer Spectroscopy at room temperature displays magnetic and non-magnetic parts. The non-magnetic part has the hyperfine parameters corresponding to predominant nonstoichiometric wustite. Octahedral (Fe+2/Fe3+) and tetrahedral Fe+3 hyperfine fields of 46.0 and 49.4 T values respectively are associated to nonstoichiometric magnetite and another sextet with a hyperfine field of 52.0 T is related to hematite.

Stochastic simulation of reference rainfall scenarios for hydrological applications using a universal multifractal approach

Hydrological applications such as storm-water management or flood design usually deal with and are driven by region-specific reference rainfall regulations or guidelines based on Intensity-Duration-Frequency (IDF) curves. IDF curves are usually obtained via frequency analysis of rainfall data using which the exceedance probability of rain intensity for different durations are determined. It is also rather common for reference rainfall to be expressed in terms of precipitation P, accumulated in a duration D (related to rainfall intensity ), with a return period T (inverse of exceedance probability). Meteorological modules of hydro-meteorological models used for the aforementioned applications therefore need to be capable of simulating such reference rainfall scenarios. The multifractal cascade framework, since it incorporates physically realistic properties of rainfall processes (non-homogeneity or intermittency, scale invariance and extremal statistics) seems to suit this purpose. Here we propose a discrete-in-scale universal multifractal (UM) cascade based approach. Daily, Hourly and six-minute rainfall time series datasets (with lengths ranging from 100 to 15 years) over three regions (Paris, Nantes, and Aix-en-Provence) in France that are characterized by different climates are analyzed to identify scaling regimes and estimate corresponding UM parameters (α, C1) required by the UM cascade model. Suitable renormalization constants that correspond to the P, D, T values of reference rainfall are used to simulate an ensemble of reference rainfall scenarios, and the simulations are finally compared with datasets. Although only purely temporal simulations are considered here, this approach could possibly be generalized to higher spatial dimensions as well.

The protoliths of central Himalayan eclogites

Eclogites represent the highest pressure conditions yet observed from rocks thrust to the surface in the central Himalaya. A detailed investigation of the protolith nature of these eclogites is needed to better understand pre-Himalayan geological history. Retrogressed eclogites were collected from Thongmön (Dingri County) and Riwu (Dinggye County), central Himalaya, China. We investigated the bulk rock major and trace elements, Sr-Nd isotopes, zircon geochronology, and Hf-O isotopes. These retrogressed eclogites experienced five stages of metamorphic evolution from prograde amphibolite-facies to peak eclogite-facies, and high pressure granulites-facies, granulites-facies then final amphibolite-facies overprinting during exhumation. Geochemically, they are subalkaline basalts with high FeO contents and a tholeiitic affinity; trace elements show similarities with enriched mid-ocean ridge basalts. Bulk rocks have a wide range of εNd(t) values from −0.24 to +7.08, and an unusually wide range of initial 87Sr/86Sr ratios of 0.705961−0.821182. Zircon relict magmatic cores from both Thongmön and Riwu eclogites yield a consistent protolith age of ca. 1850 Ma, with enriched heavy rare earth element patterns and significant negative Eu anomalies. These relict cores have oxygen isotopes signatures of δ18O = 5.8−8.1‰, εHf(t) values of −4.85 to +9.59, and two-stage model ages (TDM2) of 1.91−2.81 Ga. Metamorphic overgrowth zircons yield much younger ages of ca. 14 Ma. Integration of all of the above data suggests that the protolith of these central Himalayan retrogressed eclogites might be Proterozoic continental flood basalts of the North Indian Plate, generated under a post-collisional extension setting during the assembly of the Columbia Supercontinent. Occurrence of both Neoproterozoic−early Paleozoic rocks and ca. 1.85 Ga rocks in the regional crystalline rocks may reflect either unrecognized sub-horizontal Main Central Thrust exposure(s) or exhumation of a deeply cut part of the Greater Himalayan Crystalline complex. In combination with previous reports of Late Cretaceous, Neoproterozoic, and similar but younger Paleoproterozoic protolith, it is clear that the central Himalayan eclogites originate from multiple sources of protolith.

Magmatism and related metamorphism as a response to mountain-root collapse of the Dabie orogen: Constraints from geochronology and petrogeochemistry of metadiorites

Post-collisional mountain-root collapse and subsequent massive partial melting occurred in the high-temperature (HT) ultrahigh-pressure (UHP) metamorphic terrane of the North Dabie complex zone (NDZ), central China. The NDZ was deeply subducted in the Triassic, producing widespread migmatites and various magmatic intrusions in the Cretaceous. Post-collisional metadiorites with distinctive large K-feldspar augen porphyroblasts, locally reported but rarely exposed in the NDZ, underwent a complex evolutional history. In this contribution, integrated studies including field investigation, petrographic observation and mineral analysis, zircon U-Pb geochronological and Hf isotopic analyses, and whole-rock elemental and Sr-Nd-Pb isotopic analyses of the metadiorites were carried out. Our results provide new constraints on the mountain-root collapse in the Dabie orogen. The metadiorites are enriched in large ion lithophile elements and light rare earth elements, whereas they are depleted in high field strength elements and heavy rare earth elements with significant Ba positive anomalies, a composition consistent with the lower continental crust. All the studied samples have moderately enriched initial 87Sr/86Sr ratios (0.707582−0.708099), low εNd(t) values (−15.3 to −20.4), and low initial Pb isotopic ratios (16.0978−16.8452, 15.3167−15.4544, and 37.1778−37.8397 for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, respectively). However, they have highly negative εHf(t) values and Paleoproterozoic two-stage Hf model ages, which are only partially consistent with data from the associated UHP metamorphic rocks. Such features suggest the metadiorites resulted from a magma produced by mixing of Triassic UHP mafic lithologies and minor amounts of mantle-derived materials. Zircon morphological analysis and U-Pb sensitive high-resolution ion microprobe dating combined with conventional thermobarometry indicate that these upwelling melts crystallized at pressure-temperature (P-T) conditions of 5.4−5.7 kbar and 750−768 °C at ca. 130 Ma and subsequently suffered HT metamorphism at ca. 125 Ma. We conclude that the metadiorites’ precursors were derived from partial melting of the Triassic subducted Neoproterozoic mafic lower-crustal rocks, with addition of minor amounts of mantle-derived materials in the Early Cretaceous, in response to mountain-root collapse of the orogen. Based on petrographic textures and mineral compositions, it is moreover inferred that formation of the distinctive K-feldspar porphyroblasts is likely related to a two-stage process, i.e., crystallization derived from biotite breakdown after the formation of the metadiorite at T = 640−703 °C and P < 4.5 kbar and coarsening related to shear deformation.

Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean

The origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock geochemical and Sr–Nd isotope features as well as U–Pb–Hf isotope characteristics of zircon crystals for newly identified Early Devonian volcanic rocks from the northern margin of YB. The volcanic rocks are composed of rhyolite, rhyolite porphyry, and rhyolitic tuff. Zircon U-Pb age dating indicates they were formed at ca. 407~418 Ma. They have high SiO2 (70.16–77.52 wt.%) and alkali (5.10–9.56 wt.%) contents, and high Zr + Nb + Ce + Y content (~456 ppm), indicative of A-type magma. Their relative depletion of Nb, Ta, and Ti, and enrichment of LILEs show arc affinity. Their low initial 87Sr/86Sr ratios (0.699708–0.709822) and negative εNd(t) values (−1.8 to −4.0) indicate a mainly continental magma source and their positive εHf(t)values (+6.13 to +14.81) are possibly due to the garnet effect. All these above reveal that volcanic rocks were generated by re-melting of lower crust under a high temperature condition, which was induced by long-lived heat accumulation with no or minimal basalt flux. Combined with active continental margin inference evidenced by contemporaneous sedimentary rocks, we attribute the generation of the volcanic rocks to a continental arc setting related to the southward subduction of Junggar oceanic crust. Thus, we infer the Early–Middle Devonian arc-related magmatic rocks in the northern margin of YB are eastward counterparts of the southern limb of the Devonian Volcanic Belt, which resulted from a relatively steady-state southward subduction.

Liquidity Choice: A Study of Theoretical and Empirical Mystery in Context of Pakistan

Contextual difference and inclusion of demographics as independent as well as new dimension of Liquidity preferencemade the study unique and novel in its essence. Empirical result of the correlation matrix is showing aninsignificant correlation of liquidity preference with gender, age, education, experience, annual income, annual savings, occupation and location.Regression analysis depicts significant relationship of liquidity preferencewith Education and Savings given by t-values -2.129, 2.190 and p-values -0 .620, 0.029 respectively.Liquidity preference is showing an insignificant relationship with Gender, Age, Experience, Income and Occupation given by t-values 0.117, 0.076, -1.220, -0.708,-0.144 and p-values .009, 006,-.120,-.075 and -.011 respectively.