@article{SokolHalamaMeliksetianetal.2018, author = {Sokol, Krzysztof and Halama, Ralf and Meliksetian, Khachatur and Savov, Ivan P. and Navasardyan, Gevorg and Sudo, Masafumi}, title = {Alkaline magmas in zones of continental convergence}, series = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, volume = {320}, journal = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0024-4937}, doi = {10.1016/j.lithos.2018.08.028}, pages = {172 -- 191}, year = {2018}, abstract = {Alkaline igneous rocks are relatively rare in settings of tectonic convergence and little is known about their petrogenesis in these settings. This study aims to contribute to a better understanding of the formation of alkaline igneous rocks by an investigation of the Tezhsar volcano-intrusive alkaline ring complex (TAC) in the Armenian Lesser Caucasus, which is located between the converging Eurasian and Arabian plates. We present new petrological, geochemical and Sr Nd isotope data for the TAC to constrain magma genesis and magma source characteristics. Moreover, we provide a new Ar-40/Ar-39 age of 41.0 +/- 0.5 Ma on amphibole from a nepheline syenite that is integrated into the regional context of ongoing regional convergence and widespread magmatism. The TAC is spatially concentric and measures similar to 10 km in diameter representing the relatively shallow plumbing system of a major stratovolcano juxtaposed by ring faulting with its extrusive products. The plutonic units comprise syenites and nepheline syenites, whereas the extrusive units are dominated by trachytic-phonolitic rocks. The characteristic feature of the TAC is the development of pseudomorphs after leucite in all types of the volcanic, subvolcanic and intrusive alkaline rocks. Whole-rock major element data show a metaluminous (Alkalinity Index = 0-0.1), alkalic and silica-undersaturated (Feldspathoid Silica-Saturation Index <0) character of the TAC. The general trace element enrichment and strong fractionation of REEs (La-N/Yb-N up to 70) indicate a relatively enriched magma source and small degrees of partial melting. All TAC rocks show a negative Nb Ta anomalies typical of subduction zone settings. The initial 87Sr/85Sr ratios (0.704-0.705) and positive sNd values (+3 to +5) indicate an isotopically depleted upper mantle and lack of significant crustal influence, which in turn suggests the TAC magma has formed via differentiation from lithospheric mantle melts.}, language = {en} } @article{LopezAltenbergerBellosetal.2019, author = {Lopez, Jose P. and Altenberger, Uwe and Bellos, Laura I. and G{\"u}nter, Christina}, title = {The Cumbres Calchaquies Range (NW-Argentina)}, series = {Journal of South American earth sciences}, volume = {93}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2019.03.016}, pages = {480 -- 494}, year = {2019}, abstract = {The Cumbres Calchaquies Range forms part of the Famatinian metamorphic basement of the Eastern Sierras Pampeanas. The sedimentary protoliths of the metamorphic sequence were deposited in a marine basin alongside the western margin of Gondwana during the Neoproterozoic. New petrologic, geochemical and thermobarometric data give insight into the evolution of the sedimentary basin, its sediment source area, its later metamorphic overprint and its regional relationship to other parts of the Famatinian basement. The metamorphic series studied here consists of banded schists and gneisses and rare calcsilcate-rocks and migmatites that have been reworked by mid-to deep-crustal metamorphic and tectonic processes. The bulk rock compositions indicate shale, wacke, marl and litharenitic protoliths. The metamorphosed elastic sediments have major and trace element compositions indicating a continental granitoid-dominated source area with low sediment recycling. Low SiO2/Al2O3 ratios suggest a relatively low maturity of the sedimentary protoliths. Therefore, the Cumbres Calchaquies section represents a sequence of turbidity currents with progressive shallowing of the depositional environment, as indicated by quartz- and carbonate-rich sediments. The overall data are consistent with the geodynamic environment of a basin adjacent to a continental magmatic arc as the most probable scenario. Whereas the sedimentary protoliths of the metamorphic basement in the Sierra de Ancasti and Sierra de Aconquija, located ca 100-300 km south of the study area are interpreted as originating in an evolving back-arc basin, our results from the Cumbres Calchaquies region indicate a sedimentary source in a felsic continental arc with no significant influx of basic rocks. The Famatinian metamorphic evolution of the Cumbres Calchaquies rocks is of typical Barrow-type, culminating in partial melting of the metasediments. Conventional thermobarometry combined with thermodynamic models (pseudosections) reveal a prograde evolution reaching peak conditions of ca 665 degrees C/6.1 Kbar. This implies a geothermal gradient of ca 35 degrees C/km, which is slightly higher than the average for continental crust and suggests a period of crustal thinning, as known from back-arc basins, or additional heat supply by voluminous intrusions.}, language = {en} } @article{JentschDuesingJolieetal.2021, author = {Jentsch, Anna and D{\"u}sing, Walter and Jolie, Egbert and Zimmer, Martin}, title = {Monitoring the response of volcanic CO2 emissions to changes in the Los Humeros hydrothermal system}, series = {Scientific reports}, volume = {11}, journal = {Scientific reports}, number = {1}, publisher = {Macmillan Publishers Limited, part of Springer Nature}, address = {[London]}, issn = {2045-2322}, doi = {10.1038/s41598-021-97023-x}, pages = {11}, year = {2021}, abstract = {Carbon dioxide is the most abundant, non-condensable gas in volcanic systems, released into the atmosphere through either diffuse or advective fluid flow. The emission of substantial amounts of CO2 at Earth's surface is not only controlled by volcanic plumes during periods of eruptive activity or fumaroles, but also by soil degassing along permeable structures in the subsurface. Monitoring of these processes is of utmost importance for volcanic hazard analyses, and is also relevant for managing geothermal resources. Fluid-bearing faults are key elements of economic value for geothermal power generation. Here, we describe for the first time how sensitively and quickly natural gas emissions react to changes within a deep hydrothermal system due to geothermal fluid reinjection. For this purpose, we deployed an automated, multi-chamber CO2 flux monitoring system within the damage zone of a deep-rooted major normal fault in the Los Humeros Volcanic Complex (LHVC) in Mexico and recorded data over a period of five months. After removing the atmospheric effects on variations in CO2 flux, we calculated correlation coefficients between residual CO2 emissions and reinjection rates, identifying an inverse correlation of rho = - 0.51 to - 0.66. Our results indicate that gas emissions respond to changes in reinjection rates within 24 h, proving an active hydraulic communication between the hydrothermal system and Earth's surface. This finding is a promising indication not only for geothermal reservoir monitoring but also for advanced long-term volcanic risk analysis. Response times allow for estimation of fluid migration velocities, which is a key constraint for conceptual and numerical modelling of fluid flow in fracture-dominated systems.}, language = {en} } @article{JanssenArhonditsisBeusenetal.2015, author = {Janssen, Annette B. G. and Arhonditsis, George B. and Beusen, Arthur and Bolding, Karsten and Bruce, Louise and Bruggeman, Jorn and Couture, Raoul-Marie and Downing, Andrea S. and Elliott, J. Alex and Frassl, Marieke A. and Gal, Gideon and Gerla, Daan J. and Hipsey, Matthew R. and Hu, Fenjuan and Ives, Stephen C. and Janse, Jan H. and Jeppesen, Erik and Joehnk, Klaus D. and Kneis, David and Kong, Xiangzhen and Kuiper, Jan J. and Lehmann, Moritz K. and Lemmen, Carsten and Oezkundakci, Deniz and Petzoldt, Thomas and Rinke, Karsten and Robson, Barbara J. and Sachse, Rene and Schep, Sebastiaan A. and Schmid, Martin and Scholten, Huub and Teurlincx, Sven and Trolle, Dennis and Troost, Tineke A. and Van Dam, Anne A. and Van Gerven, Luuk P. A. and Weijerman, Mariska and Wells, Scott A. and Mooij, Wolf M.}, title = {Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective}, series = {Aquatic ecology : the international forum covering research in freshwater and marine environments}, volume = {49}, journal = {Aquatic ecology : the international forum covering research in freshwater and marine environments}, number = {4}, publisher = {Springer}, address = {Dordrecht}, issn = {1386-2588}, doi = {10.1007/s10452-015-9544-1}, pages = {513 -- 548}, year = {2015}, abstract = {Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.}, language = {en} } @article{HeineckeMischkeAdleretal.2017, author = {Heinecke, Liv and Mischke, Steffen and Adler, Karsten and Barth, Anja and Biskaborn, Boris K. and Plessen, Birgit and Nitze, Ingmar and Kuhn, Gerhard and Rajabov, Ilhomjon and Herzschuh, Ulrike}, title = {Climatic and limnological changes at Lake Karakul (Tajikistan) during the last similar to 29 cal ka}, series = {Journal of paleolimnolog}, volume = {58}, journal = {Journal of paleolimnolog}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-2728}, doi = {10.1007/s10933-017-9980-0}, pages = {317 -- 334}, year = {2017}, abstract = {We present results of analyses on a sediment core from Lake Karakul, located in the eastern Pamir Mountains, Tajikistan. The core spans the last similar to 29 cal ka. We investigated and assessed processes internal and external to the lake to infer changes in past moisture availability. Among the variables used to infer lake-external processes, high values of grain-size end-member (EM) 3 (wide grain-size distribution that reflects fluvial input) and high Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes), are indicative of moister conditions. High values in EM1, EM2 (peaks of small grain sizes that reflect long-distance dust transport or fine, glacially derived clastic input) and TiO2 (terrigenous input) are thought to reflect greater influence of dry air masses, most likely of Westerly origin. High input of dust from distant sources, beginning before the Last Glacial Maximum (LGM) and continuing to the late glacial, reflects the influence of dry Westerlies, whereas peaks in fluvial input suggest increased moisture availability. The early to early-middle Holocene is characterised by coarse mean grain sizes, indicating constant, high fluvial input and moister conditions in the region. A steady increase in terrigenous dust and a decrease in fluvial input from 6.6 cal ka BP onwards points to the Westerlies as the predominant atmospheric circulation through to present, and marks a return to drier and even arid conditions in the area. Proxies for productivity (TOC, TOC/TN, TOCBr), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC, delta(18) OCarb) indicate changes within the lake. Low productivity characterised the lake from the late Pleistocene until 6.6 cal ka BP, and increased rapidly afterwards. Lake level remained low until the LGM, but water depth increased to a maximum during the late glacial and remained high into the early Holocene. Subsequently, the water level decreased to its present stage. Today the lake system is mainly climatically controlled, but the depositional regime is also driven by internal limnogeological processes.}, language = {en} } @article{BsdokAltenbergerConchaPerdomoetal.2020, author = {Bsdok, Barbara and Altenberger, Uwe and Concha-Perdomo, Ana Elena and Wilke, Franziska Daniela Helena and Gil-Rodriguez, J. G.}, title = {The Santa Rosa de Viterbo meteorite, Colombia}, series = {Journal of South American earth sciences}, volume = {104}, journal = {Journal of South American earth sciences}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0895-9811}, doi = {10.1016/j.jsames.2020.102779}, pages = {8}, year = {2020}, abstract = {Undifferentiated meteorites, like primitive chondrites, can contain presolar and solar nebula materials which would provide information about the origin and initial conditions of the solar system, whereas differentiated meteorites like iron meteorites, can show early phases of planetary accretion. They also provide the possibility to receive information about core properties and planetary bodies. In addition to the gain in such fundamental scientific knowledge both types are of interest for the exploration of critical raw materials (CRMs) and precious elements. The Santa Rosa de Viterbo meteorite shower, discovered 1810 in the Boyaca province of Colombia, represents a typical iron-nickel meteorite. The present study presents new structural, textural and geochemical results of one fragment of this meteorite, using reflecting microscopy, electron probe micro analyses (EPMA) and electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The present study presents trace element concentrations of the meteorite's minerals for the first time. The sample is dominated by kamacite (alpha-FeNi). Schreibersite (FeNi3P), taenite (gamma-FeNi) and plessite (mixture of kamacite and taenite) are minor constituents. The occurrence of cohenite ((Fe,Ni,Co)(3)C) and troilite (FeS) are likely. The meteorite sample contains classical Neuman bands passing through kamacite and frequent Widmanstadtten pattern. The bandwidth of kamacite defines the meteorite as finest octahedrite. Geochemically, it is characterized as a "Type IC meteorite". While improving the characterization and classification of the Santa Rosa de Viterbo Iron Meteorite, notable concentrations of Au (>400 ppm) and Ge (>230 ppm) alongside major elements such as Fe, Ni and Co in the bulk composition of that meteorite, were proven. Major and rock-forming minerals such as kamacite and taenite incorporate hundreds of ppm of Ge whereas schreibersite, itself a minor component in that particular meteorite, is the major source for Au (>1400 ppm). In kamacite and taenite also Ir, Pd and Ga were found in minor amounts. Nano-scale inclusions or atomic clusters called nano-nuggets may have been responsible for the high concentrations of Au, Ir, Pd and Ga. Raman and Laser-induced plasma spectroscopes installed in in space probes seems suitable exploration methods for Fe-Ni meteorites, containing Ni-concentrations > 5.8 wt\% defining the meteorite as octaedrites.}, language = {en} } @article{AminovDingMamadjonovetal.2017, author = {Aminov, Jovid and Ding, Lin and Mamadjonov, Yunus and Dupont-Nivet, Guillaume and Aminov, Jamshed and Zhang, Li-Yun and Yoqubov, Shokirjon and Aminov, Javhar and Abdulov, Sherzod}, title = {Pamir Plateau formation and crustal thickening before the India-Asia collision inferred from dating and petrology of the 110-92 Ma Southern Pamir volcanic sequence}, series = {Gondwana research : international geoscience journal ; official journal of the International Association for Gondwana Research}, volume = {51}, journal = {Gondwana research : international geoscience journal ; official journal of the International Association for Gondwana Research}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1342-937X}, doi = {10.1016/j.gr.2017.08.003}, pages = {310 -- 326}, year = {2017}, abstract = {The formation of the Pamir is a key component of the India-Asia collision with major implications for lithospheric processes, plateau formation, land-sea configurations and associated climate changes. Although the formation of the Pamir is traditionally linked to Cenozoic processes associated with the India-Asia collision, the contribution of the Mesozoic tectonic evolution remains poorly understood. The Pamir was formed by the suturing of Gondwanan terranes to the south margin of Eurasia, however, the timing and tectonic mechanisms associated with this Mesozoic accretion remain poorly constrained. These processes are recorded by several igneous belts within these terranes, which are not well studied. Within the Southern Pamir, the Albian-Turonian volcanic rocks and comagmatic plutons of the Kyzylrabat Igneous Complex (KIC) provide an important and still unconstrained record of the Pamir evolution. Here we provide the age, origin and the geodynamic setting of the KIC volcanics by studying their petrology, zircon U-Pb geochronology, geochemistry and isotope composition.17 samples from the KIC volcanics yield U-Pb ages spanning from 92 to 110 Ma. The volcanics are intermediate to acidic in composition (SiO2 = 56-69 wt\%) and exhibit high-K calc-alkaline and shoshonitic affinity (K2O/Na2O = 12.2 wt\%). They show enrichment in LILE and LREE and depletion in HFSE and HREE with negative Ta, Ti and Nb anomalies, suggesting an arc-related tectonic setting for their formation. Low sNd(t) values (from 9.1 to 4.7), relatively high Sr-87/Sr-86(i) ratios (0.7069-0.7096) and broad range of zircon stif values (from 22.6 to 1.5) suggest a mixture of different magma sources. These features suggest that volcanics were derived by crustal under- or intraplating of an enriched subduction-related mantle shoshonitic magmas, by heating and partial melting of the lower crust, and by mixing of both magma components. Our results further imply that the KIC volcanics represent a shoshonitic suite typical of an evolution from active continental arc to post-collisional setting with a steepening of the Benioff zone and thickening of the crust toward the back-arc. This setting is best explained by the subduction- collision transition along the Shyok suture due to accretion of the Kohistan island arc to the Karakoram. This suggests that a significant part of the crustal shortening and thickening accommodated in the Pamir occurred in the Mesozoic before the India-Asia collision with implications for regional tectonic models. This further suggests the Pamir was already a major topographic feature with potentially important paleoclimate forcing such as the monsoonal circulation. (C) 2017 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.}, language = {en} }