Recently Published Documents
Petrology and Geochemistry of basaltic rocks from north western Ethiopian Plateau Continental Flood Basalt
Volcanic Lateral Collapse Processes in Mafic Arc Edifices: A Review of Their Driving Processes, Types and Consequences
Volcanic cones are frequently near their gravitational stability limit, which can lead to lateral collapse of the edifice, causing extensive environmental impact, property damage, and loss of life. Here, we examine lateral collapses in mafic arc volcanoes, which are relatively structurally simple edifices dominated by a narrow compositional range from basalts to basaltic andesites. This still encompasses a broad range of volcano dimensions, but the magma types erupted in these systems represent the most abundant type of volcanism on Earth and rocky planets. Their often high magma output rates can result in rapid construction of gravitationally unstable edifices susceptible both to small landslides but also to much larger-scale catastrophic lateral collapses. Although recent studies of basaltic shield volcanoes provide insights on the largest subaerial lateral collapses on Earth, the occurrence of lateral collapses in mafic arc volcanoes lacks a systematic description, and the features that make such structures susceptible to failure has not been treated in depth. In this review, we address whether distinct characteristics lead to the failure of mafic arc volcanoes, or whether their propensity to collapse is no different to failures in volcanoes dominated by intermediate (i.e., andesitic-dacitic) or silicic (i.e., rhyolitic) compositions? We provide a general overview on the stability of mafic arc edifices, their potential for lateral collapse, and the overall impact of large-scale sector collapse processes on the development of mafic magmatic systems, eruptive style and the surrounding landscape. Both historical accounts and geological evidence provide convincing proofs of recurrent (and even repetitive) large-scale (>0.5 km3) lateral failure of mafic arc volcanoes. The main factors contributing to edifice instability in these volcanoes are: (1) frequent sheet-like intrusions accompanied by intense deformation and seismicity; (2) shallow hydrothermal systems weakening basaltic rocks and reducing their overall strength; (3) large edifices with slopes near the critical angle; (4) distribution along fault systems, especially in transtensional settings, and; (5) susceptibility to other external forces such as climate change. These factors are not exclusive of mafic volcanoes, but probably enhanced by the rapid building of such edifices.
Exploring exchange and direct procurement strategies for Natufian food processing tools of el-Wad Terrace, Israel
AbstractWe present the results of a detailed geochemical provenance study of 54 Natufian (ca. 15,000–11,700 cal. BP) basalt pestles from the site of el-Wad Terrace (EWT), Israel. It is the first time precise locations from where basalt raw materials were derived are provided. The results indicate that the Natufian hunter-gatherers used multiple sources of basaltic rocks, distributed over a large area surrounding the Sea of Galilee. This area is located at a considerable distance from EWT, ca. 60–120 km away, in a region where contemporaneous Natufian basecamps are few. We consider two possible models that suggest vehicles for the transportation of these artifacts to EWT, namely the exchange obtaining model (EOM) and the direct procurement model (DPM). We argue that these mechanisms are not mutually exclusive and may have operated together. We also suggest that at a time of increasing Natufian territoriality, a large area around the Sea of Galilee remained unclaimed. The paper concludes with a brief discussion of the implications for the two models. In particular, we note that the DPM implies that technological know-how for pestle production was maintained within the EWT community.
Basaltic Outcrops as Centers of Diversity for Xerothermic Plants in the Sudetes Mountains (Central Europe)
Rock outcrops have promoted a high level of species diversity and provided a stable microclimate for long time periods. The present study is devoted to plant diversity of natural Quaternary outcrops of basaltic rocks. Chorological and ecological investigations were carried out at 35 such outcrops, located within five physiogeographic units of the Sudetes Mountains. The focus was on 120 xerothermic taxa of vascular plants: 62 strictly xerothermic (steppe) taxa of the Festuco valesiacae-Brometea erecti class, and 58 thermophilous taxa representing classes Trifolio medii-Geranietea sanguinei and Quercetea pubescentis. Limited geographical ranges of these plants are manifested by variable frequency of their occurrence. Species distribution is determined by natural factors, like surface area of the outcrop, the type of basaltic rock and the type of plant communities developed. Basaltic outcrops in the Sudetes meet the criterion of habitat islands (inselbergs), serve as regional centers of vascular flora, and are refugia for marginal populations of relict species.
Positron Annihilation Spectroscopy Of Basaltic Rocks From Plio-Qaternary Volcanics, Sana’a-Amran Volcanic Field, Yemen
Multi-layer perceptron-based tectonic discrimination of basaltic rocks and an application on the Paleoproterozoic Xiong'er volcanic province in the North China Craton
Sr-Nd-Pb isotopic significance of mantle source components from Central and Western Anatolia: Melting evidences from peridotite and pyroxenite source domains
<p>Extensive magmatic activities were developed in &#160;Central and Western Anatolia,&#160; since middle miocene to quaternary times,&#160;&#160; the most primitive lavas are situated in eastern end of Central (Sivas) and also western (Kula) Anatolia, besides Kula basalts are&#160; one of the most recent basaltic rocks together with&#160; basalts&#160; from south-central Anatolia.&#160; &#160;Although the magmatism is generally&#160;&#160; observed at several different&#160; locations, the recent&#160;&#160; basaltic rocks in both of the regions &#160;&#160;seem to be derived from&#160; the melting&#160; of the peridotite and pyroxenite &#160;source &#160;domains and the latter one&#160; was ignored in previous studies as source component.</p><p>&#160;The previous studies indicate that many of the basaltic rocks from Central and Western Anatolia&#160; are related with spinel-garnet transition, but typical Tb/Yb(N) (>1.8; ) and Zn/Fe&#160; &#160;(separates peridotite-derived (Zn/Fe <12; ) and pyroxenite-derived (Zn/Fe 13-20);  melts)&#160; Co/Fe&#160; ratios of the basaltic rocks from&#160; several volcanic centers from Central and Western Anatolia&#160; reveal that&#160;&#160; melting from the single&#160; source component&#160; are not solely capable of&#160; the producing&#160; basaltic &#160;rocks.&#160;</p><p>&#160;Sr-Nd and Pb isotopic &#160;compositions &#160;clearly display the distinction &#160;of samples which are&#160; linked to&#160; &#160;&#160;asthenospheric source. The lead isotopic systematic &#160;shows&#160; no siginificant differences&#160; among the Central and Western Anatolian basalts,&#160; of all the samples are above the NHRL line and close to EM II&#160; mantle component, &#160;Sr- Nd&#160; isotopes&#160; also display similar compositions as well, the majority of the samples are in and close to mantle array,&#160;&#160; but the &#160;Sr isotopic composition &#160;&#160;of&#160; Miocene aged &#160;Gediz and Simav lavas have high radiogenic values.&#160;</p><p>Tb/Yb(N),&#160; Zn/Fe ratios&#160; and &#160;&#160;as well as the Pb isotopic&#160; compositions and REE-based melting model reveal &#160;that Sivas, Erciyes Hasanda&#287;, and Develida&#287; samples in central Anatolia,&#160; and Kula, Gediz basalt in western Anatolia&#160; seem to be&#160; derived from the amalgamated melting of&#160; pyroxenite and peridotite sources, &#160;&#160;besides, &#160;the sources melting is capable of &#160;the producing&#160; &#160; &#160;elemental variations in &#160;basaltic rocks related with either lithospheric delamination or lithospheric&#160; unstability</p><ul><li>1.Wang et al., 2002, J.Geophys.Res.vol:107,ECV 5 1-21</li> <li>2 .Le Roux, et al.,2011,EPSL, vol:307, 395-408</li> </ul><p>This study is financially supported by Hacettepe University, BAB project no: FHD-2018-17283</p><p>&#160;</p>