Search

Anorthite is an important constituent mineral in basaltic achondrites from small celestial bodies. Its high‐pressure phase transformation in shocked meteorites has not been systematically studied. In this study, we report the diverse phase transformation behaviors of anorthite in a shocked eucrite Northwest Africa (NWA) 2650, which also contains coesite, stishovite, vacancy‐rich clinopyroxene, super‐silicic garnet, and reidite. Anorthite in NWA 2650 has transformed into anorthite glass (anorthite glassy vein, maskelynite, and glass with a schlieren texture and vesicles), tissintite and dissociated into three‐phase assemblage grossular + kyanite + silica glass. Different occurrences of anorthite glass might have formed via the mechanism involving shear melting, solid‐state transformation, and postshock thermally melting, respectively. Tissintite could have crystallized from a high‐pressure plagioclase melt. The nucleation of tissintite might be facilitated by relict pyroxene fragments and the early formed vacancy‐rich clinopyroxene. The three‐phase assemblage grossular, kyanite, and silica glass should have formed from anorthitic melt at high‐pressure and high‐temperature conditions. The presence of maskelynite and reidite probably suggests a minimum peak shock pressure up to 20 GPa, while the other high‐pressure phases indicate that the shock pressure during the crystallization of shock melt veins might vary from >8 GPa to >2 GPa with a heterogeneous temperature distribution. [ABSTRACT FROM AUTHOR]

The advent of the phylogenomic era has significantly improved our understanding of the evolutionary history and biogeography of Southeast Asia's diverse avian fauna. However, the taxonomy and phylogenetic relationships of many Southeast Asian birds remain poorly resolved, especially for those with large geographic ranges, which might have experienced both ancient and recent geological and environmental changes. In this study, we examined the evolutionary history and biogeography of the hill partridges (Galliformes: Phasianidae: Arborophila spp.), currently the second most speciose galliform genus, and thought to have colonized Southeast Asia from Africa. We present a well-resolved phylogeny of 14 Arborophila species inferred from ultra-conserved elements, exons, and mitochondrial genomes from both fresh and museum samples, which representing almost complete coverage of the genus. Our fossil-calibrated divergence time estimates and biogeographic modeling showed the ancestor of Arborophila arrived in Indochina during the early Miocene, but the initial divergence within Arborophila did not occur until ~10 Ma when global cooling intensified. Subsequent dispersal and diversification within Arborophila were driven by several tectonic and climatic events. In particular, we found evidence of rapid radiation in Indochinese Arborophila during the Pliocene global cooling and extensive dispersal and speciation of Sundaic Arborophila during the Pleistocene sea-level fluctuations. Taken together, these results suggest that the evolutionary history and biogeography of Arborophila were influenced by complex interactions among historical, geological and climatic events in Southeast Asia., (Copyright © 2020 Elsevier Inc. All rights reserved.)