Convective activity in a Martian magma chamber recorded by P-zoning in Tissint olivine

The Tissint Martian meteorite is an unusual depleted olivine‐phyric shergottite, reportedly sourced from a mantle‐derived melt within a deep magma chamber. Here, we report major and trace element data for Tissint olivine and pyroxene, and use these data to provide new insights into the dynamics of the Tissint magma chamber. The presence of irregularly spaced oscillatory phosphorous (P)‐rich bands in olivine, along with geochemical evidence indicative of a closed magmatic system, implies that the olivine grains were subject to solute trapping caused by vigorous crystal convection within the Tissint magma chamber. Calculated equilibration temperatures for the earliest crystallizing (antecrystic) olivine cores suggest a Tissint magma source temperature of 1680 °C, and a local Martian mantle temperature of 1560 °C during the late Amazonian—the latter being consistent with the ambient mantle temperature of Archean Earth

Diffusion-controlled and replacement microtextures in alkali feldspars from two pegmatites: Perth, Ontario and Keystone, South Dakota

Macro- and micro-perthitic microclines from pegmatites from Perth, Ontario (Wards catalogue 46 E 0510) and Keystone, South Dakota (Wards 46 E 5125) have been studied using light and electron microscopy. A sample of the type perthite from Perth, Ontario (Hunterian Museum, Glasgow, M2361) was compared using light microscopy. It differs in bulk composition and microtexture from the Wards sample. The Perth sample from Wards is a mesoperthite, with sub-periodic ~mm-thick albite veins near (100), with irregular surfaces. The microcline has regular tartan twins and formed from orthoclase by a continuous process. The Keystone sample is a microperthite, with non-periodic albite veins mainly in {110}. Irregular tartan twins, volumes of irregular microcline and subgrains suggest that the microcline formed by dissolution–reprecipitation. Microcline in both samples contains semicoherent cryptoperthitic albite films that formed after the development of tartan twins. The bulk compositions of these intergrowths imply exsolution below ~400°C. Diffusion parameters imply sustained heating for between 0.11 My at 400°C, 1.5 GPa and 8.4 My at 300°C, 1 GPa. Unrealistic times are required at 200°C. Subsequently, the crystals reacted with a fluid leading to replacive growth of the vein perthites. Unusually, Albite twin composition planes in replacive subgrains have sub-periodic dislocations, formed by coalescence of advancing growth twins. Processes that might lead to periodic, replacive intergrowths are discussed. The Perth and Keystone feldspars have been used for experimental work on dissolution during weathering and on anomalous thermoluminescence fading. Their microtextures make them unsuitable for obtaining properties that can be extrapolated to feldspars in general

Evaluating the Differences of Gridding Techniques for Digital Elevation Models Generation and Their Influence on the Modeling of Stony Debris Flows Routing: A Case Study From Rovina di Cancia Basin (North-Eastern Italian Alps)

Debris \ufb02ows are among the most hazardous phenomena in mountain areas. To cope with debris \ufb02ow hazard, it is common to delineate the risk-prone areas through routing models. The most important input to debris \ufb02ow routing models are the topographic data, usually in the form of Digital Elevation Models (DEMs). The quality of DEMs depends on the accuracy, density, and spatial distribution of the sampled points; on the characteristics of the surface; and on the applied gridding methodology. Therefore, the choice of the interpolation method affects the realistic representation of the channel and fan morphology, and thus potentially the debris \ufb02ow routing modeling outcomes. In this paper, we initially investigate the performance of common interpolation methods (i.e., linear triangulation, natural neighbor, nearest neighbor, Inverse Distance to a Power, ANUDEM, Radial Basis Functions, and ordinary kriging) in building DEMs with the complex topography of a debris \ufb02ow channel located in the Venetian Dolomites (North-eastern Italian Alps), by using small footprint full- waveform Light Detection And Ranging (LiDAR) data. The investigation is carried out through a combination of statistical analysis of vertical accuracy, algorithm robustness, and spatial clustering of vertical errors, and multi-criteria shape reliability assessment. After that, we examine the in\ufb02uence of the tested interpolation algorithms on the performance of a Geographic Information System (GIS)-based cell model for simulating stony debris \ufb02ows routing. In detail, we investigate both the correlation between the DEMs heights uncertainty resulting from the gridding procedure and that on the corresponding simulated erosion/deposition depths, both the effect of interpolation algorithms on simulated areas, erosion and deposition volumes, solid-liquid discharges, and channel morphology after the event. The comparison among the tested interpolation methods highlights that the ANUDEM and ordinary kriging algorithms are not suitable for building DEMs with complex topography. Conversely, the linear triangulation, the natural neighbor algorithm, and the thin-plate spline plus tension and completely regularized spline functions ensure the best trade-off among accuracy and shape reliability. Anyway, the evaluation of the effects of gridding techniques on debris \ufb02ow routing modeling reveals that the choice of the interpolation algorithm does not signi\ufb01cantly affect the model outcomes

Pressure-temperature-time constraints for exhumation of ultrahigh-pressure metamorphic rocks, North Qaidam terrane, Western China

Ultrahigh-pressure rocks of a Paleozoic continental suture zone are exposed in the southeastern North Qaidam terrane (Dulan region). Garnetite sample D119 contains minor Czo+Qtz+Chl+Ttn; rutile inclusions in titanite suggest that titanite replaced rutile during decompression. Pressure-temperature estimates of sample D119 are 16.1-18.4 kbar and 485-520 °C. Sample D130B is a mafic band in calc-silicate gneiss, with garnet porphyroblasts in a fine-grained Hbl-Cpx-Pl-Qtz symplectite that is interpreted as former omphacite. D130B symplectite pressure-temperature estimates are 7.7-9.4 kbar and 623-708 °C. Titanite U-Pb ages of 419.7±3.1 Ma and 415.9±4.2 Ma are interpreted to date retrogression of D119 and D130B, respectively. Average exhumation and cooling rates from ultrahigh-pressure to retrograde conditions are 6.4±6.0 mm/yr and 30±27 °C/Ma (D119) and 7.9±6.1 mm/yr and 3.9±8.0 °C/Ma (D130B). These data are compatible with early, rapid exhumation of a coherent block large enough to experience nearly-isothermal decompression in its insulated interior (D130B), while colder crust conductively refrigerates the block\u27s margins (D119)

Petrography and geochemistry of carbonate rocks of the Paleoproterozoic Zaonega Formation, Russia : Documentation of C-13-depleted non-primary calcite

The Norwegian Research Council grant 191530/V30 to V.A. Melezhik fully funded the work of AEC, VAM and AL. ATB was supported by NERC grant NE/G00398X/1 to AEF and ARP. We are grateful for sample preparation and analyses to all the personnel at NGU lab. We appreciate the work on carbon and oxygen isotope analyses by Julie Dougans and Chris Taylor. Bojan Otoničar organized and helped with the CL work at the Karst Research Institute at Postojna. Arrangement of TOC, IC, and TC analyses at University of Münster is acknowledged to Harald Strauss.Peer reviewedPostprin

Bioclimatic mapping as a new method to assess effects of climatic change

Rigorous mapping of climatic patterns outstands as one of the mayor issues concerningclimatic change. This paper investigates the extent of the bioclimatic approach to develop a rigorouscartographic methodology to express climatic diversity patterns. Michoacan, Mexico was chosen torepresent a region of complex geo-ecological layout where the Nearctic and Neotropical biogeographicalrealms converge. Bioclimatic indices were computed and their spatial expression was processed in aGeographic Information System. Ground verification was performed at 93 sites across the province. Inaddition, from 2010 until 2012, more than 2000 kilometers of roads were surveyed to gather data onisobioclimate boundaries. In total, one macrobioclimate, two bioclimate s, four thermotypes, fiveombrotypes and 14 isobioclimates were distinguished in Michoacan. The Tropical pluviseasonal bioclimatewas the predominant bioclimate, covering 56.17% of the province. The Tropical xeric covers 43.82% and theTropical pluvial is practically negligible, covering 0.01% of the entire province. The relevance of theoutcome is discussed in light of its potential use for assessing likely effects of climatic change.The National Council of Science and Technology of Mexico (CONACYT) awarded a PhD scholarship tothe first author. Financial, institutional and logisticsupport was provided by UNAM-DGAPA (projectIN202214) as well as by SUMA, former government ofthe Province of Michoacan; and project AECID 2010-2012S