Basaltic Volcanic Rocks Research Articles

The early geological history of the Moon inferred from ancient lunar meteorite Miller Range 13317

AbstractMiller Range (MIL) 13317 is a heterogeneous basalt‐bearing lunar regolith breccia that provides insights into the early magmatic history of the Moon. MIL 13317 is formed from a mixture of material with clasts having an affinity to Apollo ferroan anorthosites and basaltic volcanic rocks. Noble gas data indicate that MIL 13317 was consolidated into a breccia between 2610 ± 780 Ma and 1570 ± 470 Ma where it experienced a complex near‐surface irradiation history for ~835 ± 84 Myr, at an average depth of ~30 cm. The fusion crust has an intermediate composition (Al2O3 15.9 wt%; FeO 12.3 wt%) with an added incompatible trace element (Th 5.4 ppm) chemical component. Taking the fusion crust to be indicative of the bulk sample composition, this implies that MIL 13317 originated from a regolith that is associated with a mare‐highland boundary that is KREEP‐rich (i.e., K, rare earth elements, and P). A comparison of bulk chemical data from MIL 13317 with remote sensing data from the Lunar Prospector orbiter suggests that MIL 13317 likely originated from the northwest region of Oceanus Procellarum, east of Mare Nubium, or at the eastern edge of Mare Frigoris. All these potential source areas are on the near side of the Moon, indicating a close association with the Procellarum KREEP Terrane. Basalt clasts in MIL 13317 are from a very low‐Ti to low‐Ti (between 0.14 and 0.32 wt%) source region. The similar mineral fractionation trends of the different basalt clasts in the sample suggest they are comagmatic in origin. Zircon‐bearing phases and Ca‐phosphate grains in basalt clasts and matrix grains yield 207Pb/206Pb ages between 4344 ± 4 and 4333 ± 5 Ma. These ancient 207Pb/206Pb ages indicate that the meteorite has sampled a range of Pre‐Nectarian volcanic rocks that are poorly represented in the Apollo, Luna, and lunar meteorite collections. As such, MIL 13317 adds to the growing evidence that basaltic volcanic activity on the Moon started as early as ~4340 Ma, before the main period of lunar mare basalt volcanism at ~3850 Ma.

Effects of Natural Geographic Features on the Manufacturing Industry in Sanliurfa, Turkey

Geographical features of a place have an important effect on distribution, location, aglomeration and a variety of industrial activities. Social and economical features, along with natural geographic features such as geology, geomorphology, climate, natural vegetation, soil properties and hydrographic features also have a significant effect on industry. This study aims at determining how physical geographic features affect categories of industrial activities in Sanliurfa. For this purpose, firstly, physical geographic features of Sanliurfa and statistical data on agricultural and industrial activities in Sanliurfa were obtained. Then, effects of these physical features on other economic activities and the influence of those features on the distribution of industrial plants and industrial activities were analysed in terms of distribution, relation and casuality principles. Geological formations in Sanliurfa province occured in Neogene and also in Quaternary. These formations mostly consist of Neogene limestone, Quaternary basaltic volcanic rocks and alluvial soils. Geomorfically Sanliurfa is a slightly hilly place with plateaus and plains. The main river in Sanliurfa is the Euphrates – the biggest river of Turkey. Naural vegatation of Sanliurfa consists of steppe. These physical geographic fetaures of Sanliurfa cause intensive agricultural activites all across the province. Sanliurfa province covers 18,584 km² and 60% of this area is convenient for agriculture. As a consequence, the majority of manucturing industry in Sanliurfa is agro-based, such as food, textile, mill and apparel industries. While these categories constitute 65.43% of all industrial enterprises, the share of enterprises involving stone, clay, glass, and concrete industry is 11%, and lumber and wood industry share is only 2%.

Geochemistry and zircon U–Pb geochronology of mafic rocks in the Kaiyuan tectonic mélange of northern Liaoning Province, NE China: Constraints on the tectonic evolution of the Paleo‐Asian Ocean

The Kaiyuan tectonic mélange makes up the western part of the Kaiyuan–Yanji Accretionary Complex Belt, NE China, and there has been a long‐standing controversy about its age and tectonic setting. In this paper, we present new zircon U–Pb ages and geochemical data for the mafic rocks of the Lujiapuzi Formation in the Kaiyuan tectonic mélange, and these data provide insights into the tectonic setting during the late Paleozoic and the evolutionary history of the Paleo‐Asian Ocean in the eastern segment of the Central Asian Orogenic Belt (CAOB). SHRIMP U–Pb dating of zircons from samples of albite–actinolite schist and amphibolite yielded a crystallization age of 258 ± 5.5 Ma for the protoliths, suggesting that the protoliths formed during the late Permian. The albite–actinolite schists and amphibolites have similar geochemical characteristics, and they represent metamorphosed basaltic volcanic rocks. Major, rare earth and trace element data show that the mafic rocks have a close affinity with mid‐ocean ridge basalt. REE petrogenetic modelling indicates that the primary magma was generated through the partial melting of a mixed garnet‐ and spinel‐bearing mantle source, and assimilated crustal material and underwent crystal fractionation during ascent. The geochemical features and inherited/xenocrystic zircons in the mafic samples indicate that they formed in a tectonic setting similar to the back‐arc basin. These new findings, together with other previously published data, indicate that the Paleo‐Asian Ocean still existed in the eastern segment of the CAOB during the late Permian to Early Triassic. The Kaiyuan tectonic mélange formed during the Middle Triassic, and its formation may represent the timing of final closure of the Paleo‐Asian Ocean.

Study of a terrestrial Martian analogue: Geochemical characterization of the Meñakoz outcrops (Biscay, Spain)

AbstractThe necessity to create databases for the proper interpretation of the results obtained by the rovers that will be sent by ESA to Mars implies the study of terrestrial Martian analogues. In this work, the Meñakoz outcrops, which are basaltic volcanic rocks interbedded with Turonian sediments coming from a Cretaceous submarine volcano outcrop located in Biscay (northern Spain), have been studied and proposed as a Martian analogue. Considering that Raman and near infrared spectroscopies are two of the techniques that will go on‐board the rovers in the next planetary missions, they were used to characterize the samples collected in Meñakoz. As was expected, silicates (phyllosilicates) were the major minerals detected by those techniques in the Meñakoz samples, but also, compounds such as sulfates and oxides could be detected. Phyllosilicates are very important because they are some of the compounds that have been reported to be present on the Mars surface in previous missions and specifically in Oxia Planum, the landing site for the ExoMars 2020 rover of the ESA missions to Mars. This fact provides reasons to propose the emplacement of Meñakoz as Martian analogue.

Improved dielectric and electrical properties of PANI achieved by using low cost mineral additive

In the present study, polyaniline (PANI) conducting polymer was mechanically doped with volcanic basalt rock (VBR), sodium metasilicate (Na 2 SiO 3 ), and sodium tetraborate (borax) minerals at 10 to 50 wt%, to improve the dielectric response. The influence of these mineral additives on the complex dielectric, electrical modulus, and AC impedance spectra of the PANI was investigated. It was revealed that among the mineral additives, the highest s' is achieved for 50 wt % sodium metasilicate doped PANI composite. In addition, the appearance of peaks in the imaginary component of the electric modulus plots, for especially borax and sodium metasilicate doped samples, indicates the existence of a relaxation process. In addition, the Cole-Cole plots in the complex electrical modulus plane suggests a non-Debye type of relaxation. The single semi-circle arcs observed in Nyquist plots for PANI/Na 2 SiO 3 composites indicates a dominant grain (bulk) contribution. Moreover, the bulk resistance and capacitance values for PANI/Na 2 SiO 3 composites were found to be in the order of MΩ-GΩ and pF, respectively. While the AC conductivity spectrum of the PANI/VBR composites obeys the Nearly Constant Loss model, the PANI/Borax and PANI/Na 2 SiO 3 composites were found to obey the Super Linear Power Law model. In conclusion, the low cost Na 2 SiO 3 additive with different weight percentages for PANI shows remarkable effects on the dielectric and electrical properties.

What is Down Plunge of the Dobroyde Hill High-Sulphidation Epithermal Deposit, near Junee, NSW? An Emerging Carbonate-Base-Metal-Gold Epithermal System

Discovered by Getty Oil in 1983, the outcropping Dobroyde Hill 77k Oz gold high-sulphidation epithermal prospect is now known to transition into a carbonate base-metal epithermal gold system down plunge. The project is 50km north of Wagga Wagga and 10km north of Junee which is the far southern toe of the Junee-Narromine Volcanic Belt. It is hosted within a 4km long package of middle Ordovician andesitic to basaltic sub-marine volcanic rocks and early Silurian plagioclase and hornblende phyric shoshonitic andesite sub-marine breccias (Crawford 2014, 2017). Revival of the prospect was driven by field mapping armed with a TerraSpec Halo, ground magnetics and 3D IP and magnetic inversions (by Chris Moore, Moore Geophysics). This lead to the recognition of a 3m x 2km surficial dickite ± pyrophyllite ± kaolinite ± illite ± silica ± pyrite alteration in shoshonitic andesite breccias. Follow up drilling which targeted a zone 700m down plunge of the Dobroyde Hill resource was completed in partnership with the NSW Government through the New Frontiers cooperative drill funding scheme. This hole, NDD005, intersected a far larger system than expected, with 280m of intense dickite + pyrophyllite + kaolinite + pyrite ± illite ± silica alteration then 200m of unmistakable carbonate-base-metal-gold epithermal style alteration as presented in Corbett & Leach (1998). Evolution Mining’s giant Cowal Gold Mine (~8M Oz Resource) 120km north of Dobroyde is also characterised as carbonate-base-metal-gold epithermal. Both mineralising styles show a genetic link by overprinting relationships and both having associated broad low-grade gold and silver mineralisation with individual 1m intervals to 9.5g/t gold. NDD005 is interpreted to have stepped over the top of the main epithermal gold zone, hence the target remains open to further exploration. Additionally, this 700m down plunge gap between the new and historic drilling is completely untested and if mineralised could extend the strike length of the deposit to one kilometre.

Model of Mercury Flux Associated with Volcanic Activity.

Volcanic activity is one of the primary sources of mercury in the earth's ecosystem. In this work, volcanic rocks from four geotectonically distinct localities (the Czech Republic - intraplate, rift-related alkaline basaltic rocks; Iceland - hotspot/rift-related tholeiitic basaltic rocks; Japan - island arc calc-alkaline andesites; and Alaska - continental arc calc-alkaline dacites) were studied. Ultra-trace Hg contents in all samples ranged from 0.3 up to 6µg/kg. The highest Hg content was determined for volcanic ash from Mount Redoubt (Alaska, USA). In the case of basaltic volcanic rocks, the obtained results are about two orders of magnitude smaller than values formerly assumed for primary mercury contents in basaltic lavas. They are close to predicted Hg contents in the mantle source, i.e. below 0.5µg/kg. Hg degassing is probably a key process for the resulting Hg contents in material ejected during volcanic eruption, which is previously enriched by Hg in the shallow-crust.

Characterization of Hydrogen in Basaltic Materials With Laser‐Induced Breakdown Spectroscopy (LIBS) for Application to MSL ChemCam Data

AbstractThe Mars Science Laboratory rover, Curiosity, is equipped with ChemCam, a laser‐induced breakdown spectroscopy (LIBS) instrument, to determine the elemental composition of nearby targets quickly and remotely. We use a laboratory sample set including prepared mixtures of basalt with systematic variation in hydrated mineral content and compositionally well‐characterized, altered basaltic volcanic rocks to measure hydrogen by characterizing the H‐alpha emission line in LIBS spectra under Martian environmental conditions. The H contents of all samples were independently measured using thermogravimetric analysis. We found that H peak area increases with weight percent H for our laboratory mixtures with basaltic matrices. The increase is linear with weight percent H in the mixtures with structurally bound H up to about 1.25 wt.% H and then steepens for higher H‐content samples, a nonlinear trend not previously reported but potentially important for characterizing high water content materials. To compensate for instrument, environmental, and target matrix‐related effects on quantification of H content from the LIBS signal, we examined multiple normalization methods. The best performing methods utilize O 778‐ and C 248‐nm emission lines. The methods return comparable results when applied to ChemCam data of H‐bearing materials on Mars. The calibration and normalization methods tested here will aid in investigations of H by LIBS on Mars with ChemCam and SuperCam. Further laboratory work will aid quantification across different physical matrices and heterogeneous textures because of differences we observed in H in pelletized and natural rock samples of the same composition.

Crystallization kinetics of machinable glass ceramics produced from volcanic basalt rock

This study investigates the utilization of basalt in manufacturing machinable glass ceramics. As the fluorine and potassium phases, MgF2 and K2O added into basalt are responsible for the machinability of glass ceramics. Three different compositions containing 80%, 85%, and 90% basalt, with K2O and MgF2 as the remainder, were mixed and melted in an alumina crucible at 1500 °C. Glass samples were obtained by casting the melt into a graphite mould. Glass ceramics were prepared through subsequent crystallization heat treatment of the obtained glass. Compositional and mechanical characterizations were carried out via XRD-SEM and hardness/fracture toughness and machinability tests respectively. The effect of change in the obtained phases with basalt composition on the machinability of glass ceramics was investigated. Furthermore, crystallization kinetics of the glasses were investigated by differential thermal analysis (DTA) using the Kissinger kinetic model with several different heating rates. This study reports that basalt can be utilized in the production of machinable glass ceramics only if the basalt ratio is justified. The results showed that good machining performance was observed in low-basalt content conditions (B80), When the basalt content increased (B85 and B90), the machining capability decreased markedly. Furthermore, the crystallization activation energies decreased with increase in basalt content.

CARACTERIZAÇÃO DAS CONDIÇÕES NATURAIS DAS ÁGUAS SUBTERRÂNEAS NO MUNICÍPIO DE SÃO BORJA-RS

Com a contaminação dos recursos hídricos superficiais, a água subterrânea tem se tornando uma importante fonte hídrica para a sociedade. Porém, com o seu uso desenfreado ou até mesmo inadequado, pode torná-la imprópria para o uso humano. Com base nisso, o presente estudo tem por objetivo, avaliar alguns aspectos das águas subterrâneas do município de São Borja-RS, estudando sua vulnerabilidade a contaminação do aquífero a partir do uso do sistema GOD e mapeando-os com uso de geotecnologias. Os resultados indicam que o município apresenta em sua maior parte, uma vulnerabilidade classificada como de classes baixa e média, isso se dá a partir das formações geológicas as quais o município está inserido, sendo a Formação Sistema Aquífero Serra Geral e Sistema Aquífero Guarani, com aquíferos profundos de rochas vulcânicas basálticas tipo confinados, o que os torna com menor vulnerabilidade a contaminação.

Contemporaneous alkaline and calc-alkaline series in Central Anatolia (Turkey): Spatio-temporal evolution of a post-collisional Quaternary basaltic volcanism

This study focuses on spatio-temporal evolution of basaltic volcanism in the Central Anatolian post-collisional Quaternary magmatic province which developed along a NE-SW orientation in Turkey. This magmatic province consists of the stratovolcanoes Erciyes (ES) and Hasandag (HS), and the basaltic volcanic fields of Obruk-Zengen (OZ) and Karapınar (KA). The investigated samples range between basic to intermediate in composition (48–56wt% SiO2), and exhibit calc-alkaline affinity at ES whereas HS, OZ and KA are alkaline in composition. Based on new KAr ages and major element data, the oldest basaltic rock of ES is 1700±40ka old and exhibits alkaline character, whereas the youngest basaltic trachyandesite is 12±5ka old and calc-alkaline in composition. Most ES basaltic rocks are younger than 350ka. All samples dated from HS are alkaline basalts, ranging from 543±12ka to 2±7ka old. With the exception of one basalt, all HS basalts are ~100ka or younger in age. KAr ages range from 797±20ka to 66±7ka from OZ. All the basalt samples are alkaline in character and are older than the HS alkaline basalts, with the exception of the youngest samples. The oldest and youngest basaltic samples from KA are 280±7ka and 163±10ka, respectively, and are calc-alkaline in character. Based on thermobarometric estimates samples from OZ exhibit the highest cpx-liqidus temperature and pressure. For all centers the calculated crystallization depths are between 11 and 28km and increase from NE to SW. Multistage crystallization in magma chamber(s) located at different depths can explain this range in pressure. Harker variation diagrams coupled with least-squares mass balance calculations support fractional crystallization for ES and, to lesser extend for HS, OZ and KA. All basaltic volcanic rocks of this study are enriched in large-ion lithophile elements (LILE) and light rare earth elements (LREE). The lack of negative anomalies for high field strength elements (HFSE; Y, Yb) and the La/Nb >1 favor a shallow lithospheric source for ES, HS, OZ and KA basaltic volcanic rocks, whereas some samples bear the trace element signature of an asthenospheric mantle source. The lithospheric mantle beneath Central Anatolia may have not been affected from asthenospheric mantle directly. Negative Nb-Ta-Ti anomalies and a positive Pb spike of ES, HS, OZ and KA may be ascribed to crustal contamination or as the imprints of the previous subduction processes. According to this study, and previous studies, the effect of subduction and/or crustal contamination in Central Anatolia decreased from the Miocene to the Quaternary, and the origin of the Quaternary basaltic rocks mainly derived from subduction-related magmas enriched with sediment input rather than to slab-derived fluids. Our calculated eruption ages for the four basaltic complexes show that spatial differences predominate, whereas temporal trends are difficult to discern due to limited age resolution. According to the available geochronological, petrological and geochemical data, alkaline and calc-alkaline volcanism occurred simultaneously from distinct parental magmas.

Geochemistry of volcanic and plutonic rocks from the Nahlin ophiolite with implications for a Permo–Triassic arc in the Cache Creek terrane, northwestern British Columbia

In northwestern British Columbia, the Permian Nahlin ophiolite in the northern Cache Creek terrane comprises spinel harzburgite tectonite with minor lherzolite, lower crustal mafic and ultramafic cumulates, gabbroic rocks including dikes intruding mantle harzburgite, and basaltic volcanic and volcaniclastic rocks. New lithogeochemical data from the Menatatuline Range area confirm that plutonic and volcanic rocks of the ophiolite are tholeiitic and arc related, while only a minor component of volcanic rocks are alkaline intraplate basalts. Tholeiitic basalts of the Nahlin ophiolite represent the products of 2%–20% fractional melting, and their complementary residue may be peridotite from the ophiolite mantle section. Correlative tholeiitic volcanic sections can be found elsewhere in the northern Cache Creek terrane, and they may be linked to a regionally extensive (∼200 km) intraoceanic arc. The arc tholeiite geochemistry of the plutonic and volcanic rocks, and the highly depleted nature of the mantle residues, imply that the Nahlin ophiolite formed in a supra-subduction zone environment. The Nahlin ophiolite therefore occupied the upper plate during intraoceanic collision prior to emplacement of the Cache Creek terrane. The volumetrically minor ocean island basalt type volcanic rocks in the northern Cache Creek terrane are associated with carbonate successions bearing Tethyan fauna. These sequences are likely fragments of oceanic plateaux and their carbonate atolls sliced off of the subducting plate and are unrelated to the Nahlin ophiolite-arc system.

Eocene-Miocene igneous activity in Provence (SE France): 40Ar/39Ar data, geochemical-petrological constraints and geodynamic implications

Provence (SE France) was affected by two main phases of sporadic igneous activity during the Cenozoic. New 40Ar/39Ar laser step-heating data constrain the beginning of the oldest phase to late Eocene (40.82±0.73Ma), with activity present until early Miocene (~20Ma). The products are mainly andesites, microdiorites, dacites and basaltic andesites mostly emplaced in the Agay-Estérel area. Major- and trace-element constraints, together with SrNdPb isotopic ratios suggest derivation from a sub-continental lithosphere mantle source variably modified by subduction-related metasomatic processes. The compositions of these rocks overlap those of nearly coeval (emplaced ~38–15Ma) late Eocene-middle Miocene magmatism of Sardinia. The genesis of dacitic rocks cannot be accounted for by simple fractional crystallization alone, and may require interaction of evolved melts with lower crustal lithologies.The youngest phase of igneous activity comprises basaltic volcanic rocks with mildly sodic alkaline affinity emplaced in the Toulon area ~10Myr after the end of the previous subduction-related phase. These rocks show geochemical and isotopic characteristics akin to magmas emplaced in intraplate tectonic settings, indicating a sub-lithospheric HiMu+EM-II mantle source for the magmas, melting approximately in the spinel/garnet-lherzolite transition zone. New 40Ar/39Ar laser step-heating ages place the beginning of the volcanic activity in the late Miocene–Pliocene (5.57±0.09Ma).The emplacement of “anorogenic” igneous rocks a few Myr after rocks of orogenic character is a common feature in the Cenozoic districts of the Central-Western Mediterranean area. The origin of such “anorogenic” rocks can be explained with the activation of different mantle sources not directly modified by subduction-related metasomatic processes, possibly located in the sub-lithospheric mantle, and thus unrelated to the shallower lithospheric mantle source of the “orogenic” magmatism.

Boiling vapour-type fluids from the Nifonea vent field (New Hebrides Back-Arc, Vanuatu, SW Pacific): Geochemistry of an early-stage, post-eruptive hydrothermal system

In 2013, high-temperature vent fluids were sampled in the Nifonea vent field. This field is located within the caldera of a large shield-type volcano of the Vate Trough, a young extensional rift in the New Hebrides back-arc. Hydrothermal venting occurs as clear and black smoker fluids with temperatures up to 368°C, the hottest temperatures measured so far in the western Pacific.The physico-chemical conditions place the fluids within the two-phase field of NaCl–H2O, and venting is dominated by vapour phase fluids with Cl concentrations as low as 25mM. The fluid composition, which differs between the individual vent sites, is interpreted to reflect the specific geochemical fluid signature of a hydrothermal system in its initial, post-eruptive stage. The strong Cl depletion is accompanied by low alkali/Cl ratios compared to more evolved hydrothermal systems, and very high Fe/Cl ratios. The concentrations of REY (180nM) and As (21μM) in the most Cl-depleted fluid are among the highest reported so far for submarine hydrothermal fluids, whereas the inter-element REY fractionation is only minor.The fluid signature, which has been described here for the first time in a back-arc setting, is controlled by fast fluid passage through basaltic volcanic rocks, with extremely high water-rock ratios and only limited water-rock exchange, phase separation and segregation, and (at least) two-component fluid mixing. Metals and metalloids are unexpectedly mobile in the vapour phase fluids, and the strong enrichments of Fe, REY, and As highlight the metal transport capacity of low-salinity, low-density vapours at the specific physico-chemical conditions at Nifonea. One possible scenario is that the fluids boiled before the separated vapour phase continued to react with fresh glassy lavas. The mobilization of metals is likely to occur by leaching from fresh glass and grain boundaries and is supported by the high water/rock ratios. The enrichment of B and As is further controlled by their high volatility, whereas the strong enrichment of REY is also a consequence of the elevated concentrations in the host rocks. However, a direct contribution of metals such as As from magmatic degassing cannot be ruled out. The different fluid end-member composition of individual vent sites could be explained by mixing of vapour phase fluids with another fluid phase of different water/rock interaction history.

Spatio-temporal Geochemical Evolution of the SE Australian Upper Mantle Deciphered from the Sr, Nd and Pb Isotope Compositions of Cenozoic Intraplate Volcanic Rocks

Intraplate basaltic volcanic rocks ranging in age from Late Cretaceous to Holocene are distributed across southeastern Australia in Victoria and eastern South Australia. They comprise four prov- inces differentiated on the basis of age and spatial distribution. The youngest of these (<4􏱭6 Ma) is the Newer Volcanic Province (NVP), which incorporates lava flows, scoria cones and maars, distrib- uted across western and central Victoria into South Australia. The oldest eruptive rocks belong to the 95–19 Ma Older Volcanic Province, which comprises basaltic lava flows and shallow intrusions distributed across eastern and central Victoria. When examined within the broader framework of geochemical data available for Cretaceous to Cenozoic intraplate volcanism in southeastern Australia, new major, minor and trace element and Sr, Nd and Pb isotope analyses of volcanic rocks from the NVP suggest that their parental magmas originated from a distinctively different mantle source compared with that of the Older Volcanics. We propose that the magmas repre- sented by the Older Volcanics originated from low degrees of partial melting of a mixed source of Indian mid-ocean ridge basalt (MORB)-source mantle and calcio-carbonatite metasomatized sub- continental lithospheric mantle (SCLM), followed by up to 20% fractional crystallization. The mag- mas of the youngest (<500 ka) suite of the NVP (the Newer Cones) were generated by up to 13% partial melting of a garnet-rich source, followed by similar degrees of fractional crystallization. We also suggest that the temporally intermediate Euroa Volcanics (􏰂7 Ma) reflect chemical evolution from the source of the Older Volcanics to that of the Newer Cones. Furthermore, energy- constrained recharge, assimilation and fractional crystallization (EC-RAxFC) modelling suggests that the Sr isotope signature of the 􏰂4􏱭6–1Ma Newer Plains component of the NVP can be ex- plained by up to 5% upper crustal assimilation. On the basis of these results and data from the lit- erature for mantle xenoliths, we propose a geodynamic model involving decompression melting of metasomatized veins at the base of the SCLM generating the Older Volcanics and modifying the ambient asthenosphere of Indian MORB isotope character. This was followed by thermal erosion and entrainment of the resulting depleted SCLM into the modified Indian MORB-source astheno- spheric mantle, generating the Newer Cones. Such a model is in agreement with recent geophys- ical observations in the area suggesting edge-driven convection with shear-driven upwelling as a potential geodynamic model resulting in temporal upwelling in the region.

HFSE Characteristics of Basaltic Volcanic Wall Rocks Around BIFs in Benxi Area

HFSE Characteristics of Basaltic Volcanic Wall Rocks Around BIFs in Benxi Area

Electrical and impedance properties of composites: Volcanic basalt rocks

Abstract In this work, volcanic basalt rocks, which were collected from different parts of Van city located in Eastern Anatolia, have been discussed in the context of impedance properties. The real and imaginary components of dielectric constants, dielectric dissipation factor, dielectric strength, AC conductivity and s frequency exponent parameter have been determined. According to AC conductivity results, it has been determined referring to s parameters' values, correlated barrier hopping (CBH) model is valid for all volcanic basalt rock samples at high frequency region. Moreover, the critical frequency that corresponds to the change of conductivity characteristic of all basalt volcanic rocks has been determined. Furthermore, due to their low conductivities Sample-1 and Sample-2 have been suggested as promising materials for electromagnetic radiation shielding applications for the high and low frequency regions, respectively.

HOST ROCKS’ GEOCHEMISTRY AND MINERALIZATION POTENTIAL OF POLYMETALLIC EPITHERMAL QUARTZ VEINS AT SORIPESA PROSPECT AREA, SUMBAWA ISLAND, INDONESIA

The Soripesa prospect area is located at Maria village, Wawo district, Bima region in the eastern part of Sumbawa Island, Indonesia. This area is a part of Cenozoic Calc-alkaline volcanic inner Banda- Sunda Arc. There are five main polymetallic epithermal quartz veins in the Soripesa prospect area, namely, Rini vein, Jambu air vein, Dollah vein,Merpati vein, and Arif vein. The dominant lithology is a lithic-crystal tuff of andesitic and dacitic composition and bedded limestone. Major oxides and trace elements were analyzed by using X-Ray Fluorescence (XRF) to identify the host rock geochemistry. The main veins are hosted by andesitic and andesitic/ basaltic volcanic host rocks. Major elements compositions are affected by alteration. Based on the trace element data, host rocks of all veins were formed in the volcanic arc basalt (VAB) and island arc basalt (IAB) tectonic settings. Host rocks of Rini vein contain higher amount of precious and base metal elements (Zn, Cu, Pb, and Ag.etc.) than those of other host rocks. Keywords: Soripesa prospect area, lithology, tectonic setting, mineralization.

Geochronological and geochemical constraints on the petrogenesis and tectonic significance of Paleozoic dolerite dykes in the southern margin of Alxa Block, North China Craton

Dolerite dykes are common in the southern margin of Alxa Block which is the westernmost part of North China Craton. The ages and petrogenesis of the dolerite dykes, which are important for a better understanding of tectonic–magmatic evolution in the region, are uncertain. This paper reports the results of an integrated geochronological and geochemical study of the dolerite dykes in the Jinchuan area. Previously, these dolerite dykes were considered to be coeval with the ∼831Ma Jinchuan ultramafic intrusion by some researchers, despite a cross-cutting relationship for the dykes. Our new zircon U–Pb dating indicates that the dolerite dykes were emplaced at ∼424Ma, >400Ma younger than the Jinchuan intrusion. The Jinchuan dolerite dykes contain 5–9wt.% MgO and 47–51wt.% SiO2, and are characterized by light REE (rare earth elements) enrichments relative to heavy REE, pronounced negative Nb anomaly, elevated initial 87Sr/86Sr from 0.7056 to 0.7068, negative εNd from −2 to −5, and zircon εHf from −2 to −20. The trace element and isotope data are consistent with an asthenosphere-derived parental magma that experienced 10–25% crustal contamination prior to final emplacement. Since the Jinchuan dolerite dykes are 20–40Ma younger than the subduction-related basaltic volcanic rocks, blueschists and eclogites in the nearby North Qilian orogenic belt to the south, we propose that the Jinchuan dolerite dykes are the products of basaltic magmatism induced by delamination of previously subducted oceanic lithosphere and the associated asthenosphere upwelling in a post-subduction setting. The occurrence of ∼424Ma post-subduction dolerite dykes in the Jinchuan area and the ∼450Ma arc basalts to the south indicate that the southwestern margin of North China Craton was an active plate margin in Early Paleozoic.

Petrogenesis of OIB-like basaltic volcanic rocks in a continental collision zone: Late Cenozoic magmatism of Eastern Iran

Hundreds of compositionally diverse volcanoes have erupted on the Turkish–Iranian Plateau in the last 15Myr, attributed to one or more of the processes of Middle Miocene Tethyan slab break-off, localised lithospheric delamination and small-scale convection. Magmatism post-dates the initial Late Eocene or Early Oligocene Arabia–Eurasia collision by >10Myr. By contrast, in the east of the plateau in Eastern Iran there has been intermittent magmatism from the Late Oligocene to the Quaternary. Magma types include alkali basalt flows and scoria cones and adakite-like intermediate–felsic lavas and domes. New elemental and Nd–Sr–Pb–Hf isotope data from Quaternary mafic alkaline flows near Quchan in the Meshkan area in the NE of the country are combined with existing data from Miocene–Quaternary volcanic centres in the Binalud Range and the Nayband/Neh Fault zones. These mafic, incompatible element-enriched rocks, with positive Nb–Ta anomalies, are OIB-like and are argued to have formed by low-degree melting of a heterogeneous mantle source which contained DMM- and EMII-like components. At least some of the melting took place in the garnet stability field. Significant crustal contamination during magma ascent is recognised in the Nayband/Neh samples. Penecontemporaneous adakite-like rocks are argued to be high-pressure fractionates of basaltic melts which may have a separate source to the OIB-like basalts. Late Cenozoic mantle melting was aided by (1) localised extension and (2) enhanced small-scale asthenospheric convection related to Makran subduction, low mantle viscosity owing to the prior Tethyan subduction history of the region, and possibly edge-driven convection on the margin of the thickened Zagros lithosphere.