Timing of magnetite growth associated with peridotite-hosted carbonate veins in the SE Samail ophiolite, Wadi Fins, Oman

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 125(5), (2020): e2019JB018632, doi:10.1029/2019JB018632.Carbonate‐altered peridotite are common in continental and oceanic settings and it has been suggested that peridotite‐hosted carbonate represent a significant component of the carbon‐cycle and provide an important link in the CO2 dynamics between the atmosphere, hydrosphere, and lithosphere. The ability to constrain the timing of carbonate and accessory phase growth is key to interpreting the mechanisms that contribute to carbonate alteration, veining, and mineralization in ultramafic rocks. Here we examine a mantle section of the Samail ophiolite exposed in Wadi Fins in southeastern Oman where the peridotite is unconformably overlain by Late Cretaceous‐Paleogene limestone and crosscut by an extensive network of carbonate veins and fracture‐controlled alteration. Three previous 87Sr/86Sr measurements on carbonate vein material in the peridotite produce results consistent with vein formation involving Cretaceous to Eocene seawater (de Obeso & Kelemen, 2018, https://doi.org/10.1098/rsta.2018.0433). We employ (U‐Th)/He chronometry to constrain the timing of hydrothermal magnetite in the calcite veins in the peridotite. Magnetite (U‐Th)/He ages of crystal sizes ranging from 1 cm to 200 μm record Miocene growth at 15 ± 4 Ma, which may indicate (1) fluid–rock interaction and carbonate precipitation in the Miocene, or (2) magnetite (re)crystallization within pre‐existing veins. Taken together with published Sr‐isotope values, these results suggest that carbonate veining at Wadi Fins started as early as the Cretaceous, and continued in the Miocene associated with magnetite growth. The timing of hydrothermal magnetite growth is coeval with Neogene shortening and faulting in southern Oman, which points to a tectonic driver for vein (re)opening and fluid‐rock alteration.This research was supported by a National Science Foundation (NSF) Graduate Research Fellowship to E.H.G. Cooperdock, the UTChron Laboratory at The University of Texas at Austin, the Chevron (Gulf) Centennial Professorship to D.F. Stockli, and by a Sloan Foundation grant awarded to P.B. Kelemen. We are grateful to Desmond Patterson for assistance and training with He measurements and data reduction, to Jessie Maisano for technical support with the X‐Ray Computed Tomography. These data and images were produced at the High‐Resolution X‐ray Computed Tomography Facility of the University of Texas at Austin. EHGC is grateful to Jaime Barnes, Richard Ketcham, Frieder Klein and Othmar Müntener for helpful comments on an earlier version of this manuscript. Thank you to Fin Stuart and Uwe Ring for their helpful reviews, and Stephen Parman for feedback and editorial handling of the manuscript. The (U‐Th)/He data in this manuscript are available in the GeoChron repository (https://www.geochron.org) and sample IGSNs are in the SESAR database (http://www.geosamples.org).2020-10-0

IgE-Mediated Hypersensitivity Reactions to Cannabis in Laboratory Personnel

Background: There have been sporadic reports of hypersensitivity reactions to plants of the Cannabinaceae family (hemp and hops), but it has remained unclear whether these reactions are immunologic or nonimmunologic in nature. Objective: We examined the IgE-binding and histamine-releasing properties of hashish and marijuana extracts by CAP-FEIA and a basophil histamine release test. Methods: Two workers at a forensic laboratory suffered from nasal congestion, rbinitis, sneezing and asthmatic symptoms upon occupational contact with hashish or marijuana, which they had handled frequently for 25 and 16 years, respectively. Neither patient had a history of atopic disease. Serum was analyzed for specific IgE antibodies to hashish or marijuana extract by research prototype ImmunoCAP, and histamine release from basophils upon exposure to hashish or marijuana extracts was assessed. Results were matched to those of 4 nonatopic and 10 atopic control subjects with no known history of recreational or occupational exposure to marijuana or hashish. Results: Patient 1 had specific IgE to both hashish and marijuana (CAP class 2), and patient 2 to marijuana only (CAP class 2). Controls proved negative for specific IgE except for 2 atopic individuals with CAP class 1 to marijuana and 1 other atopic individual with CAP class 1 to hashish. Stimulation of basophils with hashish or marijuana extracts elicited histamine release from basophils of both patients and 4 atopic control subjects. Conclusions: Our results suggest an IgE-related pathomechanism for hypersensitivity reactions to marijuana or hashish. Copyright (C) 2011 S. Karger AG, Base

Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran

The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at ~ 18–14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of ~ 7–6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that ~ 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin

Evidence for constriction and Pliocene acceleration of east-west extension in the North Lunggar rift region of west central Tibet

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1002/tect.20086/abstract;jsessionid=36D445F6B0A54FA5B74E359605FC0AD1.f04t02The active north trending North Lunggar rift in west central southern Tibet exposes an extensional metamorphic core complex bounded by an east dipping low-angle normal fault. Apatite and zircon (U-Th)/He thermochronology and thermal modeling of the North Lunggar rift document a minimum timing for rift inception at >10 Ma and rapid footwall exhumation between 5 and 2 Ma. Miocene footwall cooling and exhumation rates were initially slow to moderate at 400°C Ma−1 and 4–10 mm a−1. Footwall isotherms were significantly compressed during rapid exhumation resulting in an elevated transient geothermal gradient between 50 and 90°C km−1. The minimum magnitude of horizontal extension for the North Lunggar rift is 8.1–12.8 km; maximum is 15–20 km, less in the south at ~10 km. Mean Pliocene extension rate is 1.2–2.4 mm a−1 in the ~120° direction. Results for the North Lunggar rift are similar in magnitude, rate, and orientation of slip to the kinematically linked Lamu Co dextral strike-slip fault to the north. This suggests a state of constrictional strain during Pliocene time along this stretch of the Bangong-Nujiang suture from which the Lamu Co fault emanates. The onset of extension in this region may be explained by crustal thickening and gravitational orogenic collapse, followed by accelerated rifting resulting from localized crustal stretching and increased magmatic activity, potentially driven by the position and northward extent of underthrusting Indian lithosphere

Megathrust Heterogeneity, Crustal Accretion, and a Topographic Embayment in the Western Nepal Himalaya : Insights From the Inversion of Thermochronological Data

Between 81 degrees 30MODIFIER LETTER PRIMEE and 83 degrees E, the Himalayan range's "perfect" arcuate shape is interrupted by an embayment. We hypothesize that thrust geometry and duplexing along the megathrust at midlower-crustal depths play a leading role in growth of the embayment as well the southern margin of the Tibetan plateau. To test this hypothesis, we conducted thermokinematic modeling of published thermochronologic data from the topographic and structural embayment in the western Nepal Himalaya to investigate the three-dimensional geometry and kinematics of the megathrust at midlower-crustal depths. Models that can best reproduce observed cooling ages suggest that the megathrust in the western Nepal Himalaya is best described as two ramps connected by a long flat that extends further north than in segments to the east and west. These models suggest that the high-slope zone along the embayment lies above the foreland limb of an antiformal crustal accretion zone on the megathrust with lateral and oblique ramps at midlower-crustal depths. The lateral and oblique ramps may have initiated by ca. 10 Ma. This process may have controlled along-strike variation in Himalayan-plateau growth and therefore development of the topographic embayment. Finally, we analyze geological and morphologic features and propose an evolution model in which landscape and drainage systems across the central-western Himalaya evolve in response to crustal accretion at depth and the three-dimensional geometry of the megathrust. Our work highlights the importance of crustal accretion at different depths in orogenic-wedge growth and that the midlower crustal accretion determines the location of plateau edge.Peer reviewe

Velocity Dependence Of One- And Two-electron Processes In Intermediate-velocity Ar16++He Collisions

We report investigations of one- and two-electron processes in the collisions of 0.9-keV/u to 60-keV/u (vp=0.19-1.55 a.u.) Ar16+ ions with He targets. The cross sections for these processes were measured by observing the final charges of the Ar ions and the recoiling target ions in coincidence. The average Q values for the capture channels were determined by measuring the longitudinal momenta of the recoiling target ions. Single capture (SC) is the dominant process and is relatively independent of the projectile energy. The two-electron transfer-ionization (TI) process is the next largest and slowly increases with projectile energy. The Q values for both SC and TI decrease with increasing projectile energy. Our data thereby suggest that electrons are captured into less tightly bound states as the collision velocity is increased. Both double capture and single ionization are much smaller and fairly independent of the projectile energy. The energy independence of SI is somewhat surprising as our energy range spans the region of the target electron velocity where ionization would be expected to increase. Our analysis suggests that the ionization process is being suppressed by SC and TI processes. © 1993 The American Physical Society

Miocene initiation and acceleration of extension in the South Lunggar rift, western Tibet: Evolution of an active detachment system from structural mapping and (U-Th)/He thermochronology

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1002/tect.20053/abstractOngoing extension in Tibet may have begun in the middle to late Miocene, but there are few robust estimates of the rates, timing, or magnitude of Neogene deformation within the Tibetan plateau. We present a comprehensive study of the seismically active South Lunggar rift in southwestern Tibet incorporating mapping, U-Pb geochronology and zircon (U-Th)/He thermochronology. The South Lunggar rift is the southern continuation of the North Lunggar rift and comprises a ~50 km N-S central horst bound by two major normal faults, the west-dipping South Lunggar detachment and the east-dipping Palung Co fault. The SLD dips at the rangefront ~20°W and exhumes a well-developed mylonite zone in its footwall displaying fabrics indicative of normal-sense shear. The range is composed of felsic orthogneiss, mafic amphibolite, and leucogranite intrusions dated at ~16 and 63 Ma. Zircon (U-Th)/He cooling ages are Oligocene through late Pliocene, with the youngest ages observed in the footwall of the SLD. We tested ~25,000 unique thermokinematic forward models in Pecube against the structural and (U-Th)/He data to fully bracket the allowable ranges in fault initiations, accelerations, and slip rates. We find that normal faulting in the SLR began in the middle Miocene with horizontal extension rates of ~1 mm a−1, and in the north accelerated at 8 Ma to 2.5–3.0 mm a−1 as faulting commenced on the SLD. Cumulative horizontal extension across the SLR ranges from <10 km in the south to 19–21 km in the north

Resonant Electron Transfer And Excitation In Two-, Three-, And Four- Electron Caq +20 And Vq +23 Ions Colliding With Helium

Significant new evidence is reported for resonant transfer and excitation in ion-atom collisions. This process, which is analogous to dielectronic recombination, occurs when a target electron is captured simultaneously with the excitation of the projectile followed by photon emission. Strong resonant behavior with structure, in agreement with theoretical calculations, is observed in the cross section for projectile K x rays coincident with single electron capture for 100-360-MeV Ca16+,17+,18+20 and 180-460-MeV V19+,20+,21+23 ions colliding with helium. © 1984 The American Physical Society

NNLO QCD predictions for the H -> WW -> l l nu nu signal at the LHC

We present a first computation of the NNLO QCD cross section at the LHC for the production of four leptons from a Higgs boson decaying into W bosons. We study the cross section for a Higgs boson mass Mh = 165 GeV; around this value a Standard Model Higgs boson decays almost exclusively into W-pairs. We apply all nominal experimental cuts on the final state leptons and the associated jet activity and study the magnitude of higher-order effects up to NNLO on all kinematic variables which are constrained by experimental cuts. We find that the magnitude of the higher-order corrections varies significantly with the signal selection cuts. As a main result we give the value of the cross section at NNLO with all selection cuts envisaged for the search for the Higgs boson.Comment: typos corrected, version accepted in JHE

Metabolomic analysis of insulin resistance across different mouse strains and diets

Insulin resistance is a major risk factor for many diseases. However, its underlying mechanism remains unclear in part because it is triggered by a complex relationship between multiple factors, including genes and the environment. Here, we used metabolomics combined with computational methods to identify factors that classified insulin resistance across individual mice derived from three different mouse strains fed two different diets. Three inbred ILSXISS strains were fed high-fat or chow diets and subjected to metabolic phenotyping and metabolomics analysis of skeletal muscle. There was significant metabolic heterogeneity between strains, diets, and individual animals. Distinct metabolites were changed with insulin resistance, diet, and between strains. Computational analysis revealed 113 metabolites that were correlated with metabolic phenotypes. Using these 113 metabolites, combined with machine learning to segregate mice based on insulin sensitivity, we identified C22:1-CoA, C2-carnitine, and C16-ceramide as the best classifiers. Strikingly, when these three metabolites were combined into one signature, they classified mice based on insulin sensitivity more accurately than each metabolite on its own or other published metabolic signatures. Furthermore, C22:1-CoA was 2.3-fold higher in insulin-resistant mice and correlated significantly with insulin resistance. We have identified a metabolomic signature composed of three functionally unrelated metabolites that accurately predicts whole-body insulin sensitivity across three mouse strains. These data indicate the power of simultaneous analysis of individual, genetic, and environmental variance in mice for identifying novel factors that accurately predict metabolic phenotypes like whole-body insulin sensitivity