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The Perseverance rover landed in Jezero crater, Mars, in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep-ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, which probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks and are preserved in minerals related to both aqueous environments. [ABSTRACT FROM AUTHOR]

Fluctuations in estimated mantle plume melt production rates suggest complex dynamics in the upper mantle including changes in plume upwelling, compositional heterogeneity within plume stems, entrainment of anomalous mantle, or other processes. Despite the implications for mantle dynamics, differences between previous studies including the methods, study areas, and types of melt volumes estimated, limit inter‐hotspot comparisons and assessment of global variability. Here, we use a consistent methodology to calculate igneous melt production through time across a suite of 12 hotspot chains located in the Pacific, Indian, and Atlantic Ocean basins. Using global data sets of topography, gravity, sediment cover, and seafloor age along with spectral methods for calculating elastic plate flexure and gravity anomalies, we estimate the total volume of igneous material at each hotspot in three components: (a) volcanic edifices, (b) flexural infill, and (c) intrusions (underplating) within the upper mantle and lower crust. Results indicate time‐averaged melt production rates across all studied hotspots range from 3.44 m3 s−1 (Cobb) to 14.75 m3 s−1 (Kerguelen), with underplating making up the largest component. Through time, melt production rates vary from 0.1 to 2.5 times average values with statistically significant periodic fluctuations of 1.1–71.5 Myr. Spectral analysis of estimated melt volumes shows total melt production varies periodically at all 12 hotspots. Excepting Galápagos, the studied hotspots exhibit multiple periodicities of melt production variability, implying complex dynamic, thermal, and/or chemical processes within the plume conduit. Moreover, we find several groups of hotspots exhibiting similar periods of melt production variability. Plain Language Summary: Mantle plumes are buoyant, ascending columns of material from deep within the Earth's mantle. The rate of ascent and volume flux of material ascending in a mantle plume is thought to vary over time, due to rheologic conditions inside the Earth or complex fluid dynamic interactions in the rising column of material. When a mantle plume reaches the surface of the planet, plume‐derived partial melts are extracted onto the surface or emplaced in the brittle lithosphere in the form of seamounts and ocean islands, forming a quasi‐linear chain of volcanic material known as a hotspot. However, the influence of variations in plume flux on the amount of melt produced at hotspots is poorly understood. Here, we estimate the amount of melt produced at 12 hotspots and analyze how melt production changes over millions of years. All 12 hotspots have regular, periodic variations in melt production with periods ranging from 1.1 to 71.5 Myr. The periodic variations presented here are consistent with models of compositionally heterogeneous mantle plumes that entrain material from deep within the Earth. We also report some hotspots share the same periodic fluctuations in melt production, which may suggest a common mechanism is responsible for periodic variations in mantle plume flux. Key Points: Melt production at 12 hotspots is quantified in three components: volcanic edifice, infill, and underplated intrusivesMelt production estimates are consistent with previous buoyancy flux estimates and reveal periodic variations in all hotspots analyzedMultiple periodic fluctuations in melt production at individual hotspots from 1.1 to 71.8 Myr suggest complex dynamics present in plumes [ABSTRACT FROM AUTHOR]

New data on the age of the intrusive and subvolcanic rocks of the Oloy zone in Chukotka hosting commercially important Au-polymetallic and Cu-porphyry ore occurrences of the Burgakhchan area are reported. The age of the intrusive rocks of the Nichan and Vukney massifs, as well as the volcanic rocks of the Zybkin Formation in the Nenkan and Vukmaam structural-facies zones of Chukotka is determined reliably for the first time. U-Pb SHRIMP dating of zircons from three monzodiorite samples from the Nichan massif and three samples from the Vukney massif related to the Ekdygkych Complex provides evidence for their Berriasian-Valanginian age with mid-weighted values from 143 to 139 ± 2 Ma. The ages obtained correlate with the age of the porphyric diorite and monzonite of the Ekdygkych massif on the Peschanka deposit and indicate the high commercial significance of the studied intrusive complexes. The ore-bearing rocks intrude the volcanogenic-sedimentary rocks of the Zybkin Formation with a U-Pb zircon age of 146.5 ± 3 Ma. [ABSTRACT FROM AUTHOR]

The Sierra Nevada de Santa Marta in NW Colombia is an isolated massif at the northernmost end of the Andes chain near the boundary with the Caribbean plate. Previous geologic mapping and K-Ar dating have shown that Jurassic plutonic and volcanic units make up a large part of the Santa Marta Massif (SMM). These rocks have been considered to be part of a Jurassic magmatic arc extending from NW Colombia to northern Chile, but without any geochemical basis for comparison. This paper reports on a geochemical and Sr-Nd-Pb isotope study of the Jurassic rocks in the SMM and provides 12 new U-Pb zircon ages from in-situ laser ICP-MS dating. The plutonic and volcanic units span a range from 45 to 78 wt.% SiO 2 , with a dominance of intermediate to felsic compositions with SiO 2 > 57 wt.%. They classify as calc-alkaline, medium to high-K, metaluminous rocks with trace-element features typical for arc-derived magma series. In terms of their major and trace-element compositions, the SMM Jurassic units overlap with contemporary plutonic and volcanic rocks from other regions of the Central and Eastern Cordilleras of Colombia, and confirm an arc affinity. The new U-Pb ages range from 176 ± 1 Ma to 192 ± 2 Ma (n = 12), with most between 180 and 188 Ma (n = 7). The initial Sr isotope ratios (at 180 Ma) are between 0.7012 and 0.7071 (n = 29), with 3 outliers attributed to mobilization of Rb and/or Sr. Nearly all samples have negative εNd (180) values between −10.3 and 0.0 (n = 30), the two exceptions being only slightly positive (1.1 and 1.9). Measured Pb isotope ratios fall in a narrow range, with 206 Pb/ 204 Pb from 18.02 to 19.95, 207 Pb/ 204 Pb from 15.56 to 15.67 and 208 Pb/ 204 Pb from 37.76 to 39.04 (n = 28). In the regional context of previous studies, these results confirm early Jurassic ages and an arc affinity for the widespread magmatism exposed in the eastern and northeastern Colombian Andes. We also note patterns in the distribution and composition of magmas. The magmatic activity in the Central Cordillera tends to be younger than in the Eastern Cordillera and is spatially more restricted to the vicinity of regional fault systems. In terms of composition, Jurassic igneous rocks in the Eastern Cordillera have systematically lower εNd (180) values than those from the Central Cordillera, whereas the Pb isotope ratios overlap. We ascribe the Nd isotope variations to heterogeneity in the mantle source and/or degree of crustal contamination, whereas the Pb isotope ratios are crust-dominated and similar throughout the region. The spatio-temporal and compositional evolution of Jurassic magmatic rocks in the Northern Andes reflect the major plate kinematic readjustment between the Triassic and the Early Jurassic in the proto-Andean margin. [ABSTRACT FROM AUTHOR]

The isotope-geochemical composition of the Early Devonian magmatic rocks of the Chanchar potassium basaltoid volcano-plutonic Complex in the Sakmar Zone (Southern Urals) has been studied for the first time. The character of the noncoherent element distribution and their ratios suggest that the melts parental to the rocks of extrusive, subvolcanic and intrusive facies were formed from a single source of the primary magma. The low concentrations of HFSE relative to the MORB composition, relatively low εSr, and high εNd suggest the formation of primary melts from the moderately depleted mantle source. The enrichment of rocks with LILE indicates a fluid mantle addition introduced to the melts during evolution of the primary magma. [ABSTRACT FROM AUTHOR]

The Tabletop Domain of the Rudall Province has been long thought an exotic entity to the West Australian Craton. Recent re-evaluation of this interpretation suggests otherwise, but is founded on limited data. This study presents the first comprehensive, integrated U-Pb geochronology and Hf-isotope analysis of igneous and metasedimentary rocks from the Tabletop Domain of the eastern Rudall Province. Field observations, geochronology and isotope results confirm an endemic relationship between the Tabletop Domain and the West Australian Craton (WAC), and show that the Tabletop Domain underwent a similar Archean-Paleoproterozoic history to the western Rudall Province. The central Tabletop Domain comprises Archean-Paleoproterozoic gneissic rocks with three main age components. Paleo-Neoarchean (ca 3400-2800 Ma) detritus is observed in metasedimentary rocks and was likely sourced from the East Pilbara Craton. Protoliths to mafic gneiss and metasedimentary rocks are interpreted to have been emplaced and deposited during the early Paleoproterozoic (ca 2400-2300 Ma), and exhibit age and isotopic affinities to the Capricorn Orogen basement (Glenburgh Terrane). Mid-late Paleoproterozoic mafic and felsic magmatism (ca 1880-1750 Ma) is assigned to the Kalkan Supersuite, which is exposed in the western Rudall Province. The Kalkan Supersuite provided the main source of detritus for mid-late Paleoproterozoic metasedimentary rocks in the Tabletop Domain. Similarities in the age and Hf-isotope compositions of detrital zircon from these metasedimentary rocks and Capricorn Orogeny basin sediments suggests that a regionally extensive, linked basin system may have spanned the northern WAC at this time. The Tabletop Domain records evidence for two metamorphic events. Mid-late Paleoproterozoic deformation (ca 1770-1750 Ma) was high-grade, regional and involved the development of gneissic fabrics. In contrast, early Mesoproterozoic (ca 1580 Ma) high-grade deformation was localised and associated with more widespread, late-stage, greenschist facies alteration. These new findings highlight that the Tabletop Domain experienced a much higher grade of deformation than previously assumed, with a Paleoproterozoic metamorphic history similar to that of the western Rudall Province. [ABSTRACT FROM AUTHOR]

A quartz-free scheelite-bearing fine- to medium-grained anorthosite occurs as a dike in the world-class Zhuxi scheelite skarn deposit of South China. The anorthosite mainly comprises An-rich plagioclase (An avg  = 91, ~90 vol%) + scheelite (~3 vol%) + apatite (~2.5 vol%) + ilmenite (~1.5 vol%) + titanite (~1 vol%), as well as minor (~2 vol%) fluorite, prehnite, chalcopyrite, pyrrhotite, pyrite, sphalerite, rutile, and uraninite. This paper reports the first occurrence of scheelite-bearing anorthosite of hydrothermal origin in a W deposit. Field, textural, mineralogical, and geochemical evidence suggest a hydrothermal genesis for the scheelite-bearing anorthosite in the Zhuxi deposit. The scheelite-bearing anorthosite formed when the Al-, Si-, P-, W-, and F-rich residual magma (fluid) was contaminated by pure limestone in a reducing environment. The formation of the scheelite-bearing anorthosite requires fertile (W-rich) metasedimentary rocks as a magmatic source, which formed granitic magma emplaced at a great depth that emanated W-enriched magmatic hydrothermal fluids during the latest stage of magma crystallization, thus producing the large-scale tungsten mineralization in the Zhuxi mine. [ABSTRACT FROM AUTHOR]

The igneous and mechanical processes controlling the formation of nodular chromite ore have been investigated through the study of a chromitite dyke emplaced in the uppermost part of the 330 m-thick dunitic mantle/crust transition zone that developed at the top of a mantle diapir in the Maqsad area of the Oman ophiolite. The dyke is parallel to the paleo-ridge axis, has a vertical extent of about 30 m and an average thickness of 2 m. It presents spectacular variations in ore texture, offering a unique opportunity to identify the zones of nodule nucleation in the upper parts of the dyke, growth in the intermediate parts and accumulation at the bottom. Nodules grew by progressive accretion of euhedral chromite grains, 100–200 μm in size, around a nucleus made essentially of olivine and plagioclase embedded in skeletal chromite. At a critical size of 2 to 3 cm, the nodules, still poorly consolidated, sunk, accumulated and compacted at the bottom of the dyke. The interstitial silicate matrix between the nodules is essentially troctolitic (high Mg (Fo~92) and high Ni (NiO ~0.35 wt%) olivine and calcic (An 83 to An 85 ) plagioclase with minor pargasite). At about mid-height, the dyke broadens significantly, reaching a width of 12 m, the center of this bulge being filled with smaller-sized nodules embedded in an anorthositic matrix. This feature is interpreted to represent a magma pocket where the melt and nodule nuclei accumulated before complete crystallization and cooling of the system. The alteration of the silicate matrix is less intense in this bulge than in the rest of the dyke. Silicate inclusions within chromite grains indicate that the parental melt of the chromite was hybrid between two endmembers: a common MORB-like melt and a silica-rich hydrous fluid or a water-rich trondhjemitic melt, possibly produced by low degree melting of hydrothermally altered gabbro and/or serpentinized peridotite from the country rocks. The Ti content in the chromite (average ~0.5 wt% TiO 2 ) from the dyke is significantly higher than that of chromites emplaced at deeper levels in the mantle/crust dunitic transition zone (DTZ) and in the harzburgitic mantle from the Maqsad area. This points to the progressive evolution of the MORB component (product of decompression melting in the diapir) during its ascent from the mantle diapir to the base of the crust. Fractional crystallization occurred in a context of buffering of compatible element concentrations (Mg, Cr, Ni) around elevated, “primitive” values through exchanges between the percolating melt and the host harzburgite and dunite. The chemical composition of both chromite and silicates is constant (i.e. evenly scattered) from the bottom to the top of the dyke and does not mimic the evolution in the ore texture nor in the size and abundance of the nodules. This implies that the parental melt composition remained globally unchanged during the formation of the ore body arguing for open system conditions during nodule formation and accumulation. The only significant evolution is observed in the central bulge where the chromite Ti content is higher (average ~0.7 wt% TiO 2 with spikes reaching several percent) confirming that this magma pocket was filled with more evolved melt. No bottom to top evolution in the XCr of chromite is observed within the dyke but individual nodules show a well-developed zoning in XCr ratio from their nucleus (XCr ~58) to their margins (XCr ~48). An increase in the TiO 2 content of chromite toward the nodules' edges is not systematic and, when present, is quite moderate. In the largest nodules, inclusions of hydrated silicates are preferentially distributed in a circle, midway between the nodule's nucleus and its edge. This garland of inclusions coincides with a positive peak in the XCr profile, while the TiO 2 profile is not affected. This implies that the zoning in XCr cannot be assigned to fractional crystallization alone. It is tentatively explained by a scenario where the nodules crossed a gradient in the proportion of the MORB vs. more reducing hydrous melt during their growth. The gradient could have been maintained by a density contrast between a buoyant hydrous silica-rich melt and denser MORB. [ABSTRACT FROM AUTHOR]

We present here new bathymetric, petrological and geochemical whole rock, glass and mineral data from the submarine Epi volcano in the New Hebrides (Vanuatu) island arc. The structure has previously been interpreted to be part of a larger caldera structure but new bathymetric data reveal that the volcanic cones are aligned along shear zones controlled by the local tectonic stress field parallel to the recent direction of subduction. We aim to test if there is an interaction between local tectonics and magmatism and to what extent the compositions of island arc volcanoes may be influenced by their tectonic setting. Primitive submarine Epi lavas and those from the neighbouring Lopevi and Ambrym islands originate from a depleted mantle wedge modified by addition of subduction zone components. Incompatible element ratios sensitive to fluid input (e.g., Th/Nb, Ce/Yb) in the lavas are positively correlated with those more sensitive to mantle wedge depletion (e.g., Nb/Yb, Zr/Nb) amongst the arc volcanoes suggesting that fluids or melts from the subducting sediments have a stronger impact on the more depleted compositions of the mantle wedge. The whole rock, glass and mineral major and trace element compositions and the occurrence of exclusively normally zoned clinopyroxene and plagioclase crystals combined with the absence of inversely zoned crystals and water-bearing phases in both mafic and evolved lavas suggest that the erupted melt was relatively dry compared to other subduction zone melts and has experienced little disequilibrium modification by melt mixing or assimilation. Our data also imply that differentiation of amphibole is not required to explain the incompatible element patterns but may rather result from extensive clinopyroxene fractionation in agreement with petrographic observations. Thermobarometric calculations indicate that the melts fractionated continuously during ascent, contrasting with fractionation during stagnation in an established crustal magma reservoir. We interpret the occurrence of this fractional crystallisation end-member in a relatively thick island arc crust (~30 km thickness) to result from isolated and relatively rapid ascent of melts, most likely through a complex system of dykes and sills that developed due to the tectonic positioning of Epi in a complex tectonic zone between a compressional environment in the north and an extensional setting in the south. We can show that the alignment of the cones largely depends on the local tectonic stress field at Epi that is especially influenced by a large dextral strike-slip zone, indicating that structural features have a significant impact on the location and composition of volcanic edifices. [ABSTRACT FROM AUTHOR]

The drilling process is one of the significant stages of rock mechanic and mining engineering. Monitoring this operation can help researchers to have accurate perspective about drilling process, physical and mechanical features of rocks and drill bit characteristics. Drilling operation generates acoustic signals as an unwanted byproduct, which could be helpful for analyzing the nature of this process. Determining the features of rock has an undeniable importance in all downstream steps of designation in mining projects. Definition of rock properties by using direct measurement tests is a time-consuming and costly process and requires high precision. Development a novel frequency based method in this research, for determining physical and rock-mechanical features of rock could be helpful for solving problems of time consumption, cost, and precision. None of the direct and indirect conventional methods is able, to provide an accessible and efficient way (in the viewpoint of cost, time consumption, and precision) for accelerating this process. This study attempts to present mathematical relations between rock mass features and dominant acoustic frequencies emitted during drilling process using Fast Fourier Transform (FFT). A novel rotary drilling machine, with the ability to record acoustic frequencies, is designed and constructed by investigators for providing this goal. All influencing parameters of drilling regime (vertical thrust force, drill bit rotational speed, diameter and material of drill bit, sound recording ability etc.) are manageable using this machine. For drilling tests and determining physical and rock mechanical characteristics, 11 volcanic rock samples are gathered in a wide range of features. After drilling tests and by analyzing acoustic signals, five dominant frequencies are extracted for each sample. Results demonstrate almost all physical-mechanical properties of volcanic rocks (uniaxial compressive strength, tensile strength, S and P-wave velocity, porosity percentage and Schmidt Rebound Number) are predictable using diverse dominant frequencies of acoustic signals. Overall, the results present novel linear models, which are able to predict rock features. [ABSTRACT FROM AUTHOR]

Based on the analysis of dynamic phenomena under the condition of high-located hard-thick (HLHT) stratum of one coal mine, along with the similar material simulation and theoretical analysis, the characteristics of bed separation development and cracks distribution under the HLHT stratum are studied. This paper proposes a discriminating method for overlying strata Three Zones considering the influence of HLHT stratum. The development laws of cracks and disaster-causing mechanism of hard-thick magmatic rock in different strata are respectively analyzed. The studies show that in line with the working face advancing direction, the height of bed separation under the magmatic rock increases in the trend of “Increase-Stability-Decrease”, and the width of bed separation increases linearly. The width of bed separation reaches the maximum before the first breaking of magmatic rock, the bed separation completely closes after the breaking. There are no obvious bed separations during the period migration of magmatic rock. Along the direction of the height of roof, the development of bed separation is characterized by bottom-up jump based on the key strata. The analyzed results of “Three zone” height obtained by the discriminate method of overlying strata Three Zones which is based on the key strata theory and the S-R instability theory are in line with the actual facts. When the hard-thick magmatic rock is in the fractured zone, large amounts of gas and water are easy to accumulate in the bed separation space and “O” ring space around the gob. The first breaking of magmatic rock may induce bed separation gas outburst and water inrush. When the hard-thick magmatic rock is in the sagging zone, the long-term stability of magmatic rock will not cause serious disasters. But with the adjacent working face mining, bed separation gas and water often become a safety hazard. [ABSTRACT FROM AUTHOR]

Post‐glacial Permian coal‐bearing sedimentary successions are traditionally interpreted as fluvially deposited within the Gondwanaland continental set‐up throughout the globe. Recent attempts to reinterpret such successions in terms of marine flooding events, mainly based on sedimentological and ichnological attributes, raised doubt on the existing palaeogeographic model of the Late Palaeozoic Gondwanaland. Reassessing these sedimentary successions using other proxies, like petrographic and geochemical properties, may provide more reliable clues to improve the present understanding. In this paper, petrographic and geochemical analysis of sandstones, sandstone–mudstone heteroliths, and mudstones of the early Permian Barakar Formation of Lower Gondwana Supergroup, Raniganj coal Basin, India, is presented to understand the provenance, palaeoweathering pattern and palaeodepositional conditions. Petrographically, the sandstones are arkosic to sub‐arkosic in nature, with abundant unstable components and heavy minerals. Clay minerals in the matrix and the mudstones are dominated by kaolinite, illite‐smectite with authigenic glauconite, indicating a marine diagenetic realm. Mineralogical assemblage attests to sedimentation in craton interior passive margin conditions. Geochemically, the lithounits show large variations in major element and trace element (including rare earth element) concentrations. Chemical index of alteration and A–CN–K ternary plot indicate moderate to strong chemical weathering, leading to deposition of compositionally immature sediments close to their source without much recycling. Ratios of major elements (e.g., MgO, K2O, Fe2O3, Al2O3, and SiO2) signify a continental–marine transitional depositional environment developed in a stable passive margin setting under gradually warming up climatic conditions. Trace element ratios manifest an estuarine depositional setting during Barakar sedimentation, comparable with modern major river mouth estuaries. Thus, this paper provides unequivocal evidence of significant marine influence during sedimentation in the Lower Gondwana basins in India, particularly during the Permian time, and signifies the importance of re‐examining the so called “continental fluvial” coal‐bearing deposits as considerably marine‐influenced. The interpretations provide important clues in understanding and reconstructing the Permian Lower Gondwana palaeogeography in eastern peninsular India. [ABSTRACT FROM AUTHOR]

In situ zircon U–Pb ages and Hf isotopic data, whole‐rock major and trace element contents, and Sr–Nd isotopic compositions are reported for Permian intrusive rocks at Shaolanghe in Eastern Inner Mongolia in order to explore the magmatic origin and tectonic significance of these rocks for the evolution of the northern margin of the North China Craton. Three intrusive rocks, quartz diorite, Xishuiquan granite, and Xinglong granite, yield zircon U–Pb ages of 285.9 ± 3.1, 274.2 ± 2.9, and 260.0 ± 8.4 Ma, respectively. The quartz diorite and Xishuiquan granite belong to the high‐K calc‐alkaline series, enriched in large ion lithophile elements (e.g., Rb) and depleted in high field strength elements (e.g., Nb and Ti). They are defined as I‐type granites. The quartz diorite has initial 87Sr/86Sr ratios of 0.7049–0.7051, εNd(t) values of −10.0 to −11.4, and εHf(t) values of −15.2 to −9.9. The εHf(t) values of the Xishuiquan granite (−4.8 to 4.0) vary in discrete segments, whereas the εNd(t) values (−12.9 to −13.3) are consistent with those of the quartz diorites (−10.0 to −11.4). A magma mixing model is proposed for the formation of the quartz diorites of the Shaolanghe region, and the Xishuiquan granite was likely derived from partial melting of the Paleoproterozoic crust with involvement of mantle components. Geochemical analyses show that the tectonic setting of the northern margin of the North China Craton during the late Palaeozoic was an Andes‐type active continental margin associated with subduction of the Paleo‐Asian Ocean plate. [ABSTRACT FROM AUTHOR]

Discriminant analysis was performed for representative sets of igneous rocks with adakitic geochemical signatures (granitoids of Archean tonalite-trondhjemite-granodiorite suites, island-arc adakites, and adakites and adakitic granitoids of collisional to postcollisional geodynamic settings). It was shown that the granitoids of Archean tonalite-trondhjemite-granodiorite suites are significantly different from islandarc adakites, as well as from collisional to postcollisional adakites and adakitic granitoids. The following discriminant function was proposed for the geodynamic classification of island arc and collisional-postcollisional adakites and adakitic granitoids on the basis of chemical composition: DF3 =-1.69324TiO2-0.25537Al2O3-0.21269FeO* + 0.06076MgO-0.09796CaO + 0.47377Na2O + 0.29270K2O + 3.57821P2O5 + 0.00431Rb + 0.00036Sr + 0.03119Y + 0.00006Zr + 0.01088Nb-0.00048Ba + 0.01366La + 0.0004Ce + 0.02319Nd-0.18584Sm + 1.29135Eu-0.62229Gd + 0.3819Dy + 2.06583Er-2.62769Yb + 1.6464. [ABSTRACT FROM AUTHOR]

The Jingdezhen ductile shear zone is evolved from the Neoproterozoic Zhangyuan ophiolite mélange belt in the eastern Jiangnan Orogen, South China. Comprehensive study of geometry, kinematics, quartz c-axis fabric, temperature-pressure conditions and geochronology were conducted in this study. The Jingdezhen shear zone extends ∼180 km along the NE orientation with two groups of subvertical foliation and subhorizontal lineation. One group of foliation strikes NEN orientation whereas another one NEE orientation. Field investigation, microscopic observation and quartz c-axis fabric show that sinistral shearing along NEN-striking foliation occurred earlier than dextral shearing along NEE-striking foliation. Syn-tectonic staurolite porphyroblasts and deformation manner of feldspar imply that sinistral shearing occurred at 530-420 ºC and 6-2 kbar. Deformation manner and c-axis fabric of quartz and pre-tectonic staurolite porphyroblasts indicate that dextral shearing took place at 420-300 ºC. LA-ICP-MS zircon U-Pb and mica 40Ar/39Ar dating indicate that the sinistral shearing occurred during Neoproterozoic orogeny (830-800 Ma) whereas the dextral shearing at 447±12 Ma. The sinistral shearing resulted from the Neoproterozoic final assembly between the Yangtze and Cathaysia blocks. The dextral shearing was caused by Early Paleozoic orogen parallel extension and clockwise rotation. [ABSTRACT FROM AUTHOR]

Igneous sills and dykes that intrude pervasively into prospective sedimentary basins are a common occurrence in volcanic margins, impacting the petroleum system and causing geological and technical drilling challenges during hydrocarbon exploration. The Faroe-Shetland Basin (FSB), NE Atlantic Margin, has been the focus of exploration for over 45 years, with many wells penetrating igneous intrusions. Utilising 29 FSB wells (with 251 intrusions) and 3D seismic data, this study presents new insights into the impacts that igneous intrusions have on hydrocarbon exploration. Examination of cores reveals additional igneous material in individual wells, compared to estimates using seismic or petrophysical data alone, leading to potential underestimation of the volume of the igneous component in a basin. Furthermore, analysis of petrophysical data shows that within the FSB there are silicic intrusions such as diorite and rhyolite, in addition to the commonly encountered mafic intrusions. These silicic intrusions are difficult to recognise in seismic and petrophysical data due to their low density and compressional velocity and have historically been misidentified on seismic reflection data as exploration targets. Drilling data acquired through intrusions provide valuable insight into the problems exploration wells can encounter, often unexpectedly, many of which can be detrimental to safe drilling practice and result in prolonged non-productive time. [ABSTRACT FROM AUTHOR]

X-ray Synchrotron Radiation Micro-Computed Tomography (SR-µCT) allows a better visualization in three dimensions with a higher spatial resolution, contributing for the discovery of aspects that could not be observable through conventional radiography. The automatic segmentation of SR-µCT scans is highly valuable due to its innumerous applications in geological sciences, especially for morphology, typology, and characterization of rocks. For a great number of µCT scan slices, a manual process of segmentation would be impractical, either for the time expended and for the accuracy of results. Aiming the automatic segmentation of SR-µCT geological sample images, we applied and compared Energy Minimization via Graph Cuts (GC) algorithms and Artificial Neural Networks (ANNs), as well as the well-known K -means and Fuzzy C-Means algorithms. The Dice Similarity Coefficient (DSC), Sensitivity and Precision were the metrics used for comparison. Kruskal-Wallis and Dunn's tests were applied and the best methods were the GC algorithms and ANNs (with Levenberg-Marquardt and Bayesian Regularization). For those algorithms, an approximate Dice Similarity Coefficient of 95% was achieved. Our results confirm the possibility of usage of those algorithms for segmentation and posterior quantification of porosity of an igneous rock sample SR-µCT scan. [ABSTRACT FROM AUTHOR]

This work examines the global distribution of Archaean and modern igneous rock's compositions, without relying on preconceptions about the link between rock compositions and tectonic sites (in contrast with “geotectonic” diagrams). Rather, Archaean and modern geochemical patterns are interpreted and compared in terms of source and melting conditions. Mafic rocks on the modern Earth show a clear chemical separation between arc and non-arc rocks. This points to the first order difference between wet (arc) and dry (mid-ocean ridges and hotspots) mantle melting. Dry melts are further separated in depleted (MORB) and enriched (OIB) sources. This three-fold pattern is a clear image of the ridge/subduction/plume system that dominates modern tectonics. In contrast, Archaean mafic and ultramafic rocks are clustered in an intermediate position, between the three main modern types. This suggests that the Archaean mantle had lesser amounts of clearly depleted or enriched portions; that true subductions were rare; and that the distinction between oceanic plateaus and ridges may have been less significant. Modern granitic rocks dominantly belong to two groups: arc-related granitoids, petrologically connected to arc basalts; and collision granitoids, related to felsic sources. In contrast, the Archaean record is dominated by the TTG suite that derives from an alkali-rich mafic source (i.e. altered basalt). The geochemical diversity of the TTG suite points to a great range of melting depths, from ca. 5 to > 20 kbar. This reveals the absence of large sedimentary accumulations, again the paucity of modern-like arc situations, and the importance played by reworking of an earlier basaltic shell, in a range of settings (including some proto-subduction mechanisms). Nonetheless, granitoids in each individual region show a progressive transition towards more modern-looking associations of arc-like and peraluminous granites. Collectively, the geochemical evidence suggests an Archaean Earth with somewhat different tectonic systems. In particular, the familiar distinction between collision, arcs, ridges and hotspots seems to blur in the Archaean. Rather, the large-scale geochemical pattern reveals a long-lived, altered and periodically resurfaced basaltic crust. This protocrust is reworked, through a range of processes occurring at various depths that correspond to a progressive stabilization of burial systems and the establishment of true subductions. A punctuated onset of global plate tectonics is unlikely to have occurred, but rather short-term episodes of proto-subduction in the late Archaean evolved over time into longer-term, more stable style of plate tectonics as mantle temperature decayed. [ABSTRACT FROM AUTHOR]

The Kukuluma Intrusive Complex (KIC) is a late Archean igneous complex, dominated by monzonite and diorite with subordinated granodiorite. The monzonite and the diorite suites have low silica content (SiO 2  ≤ 62 wt%), moderate Mg# (Mg# average  = 49), high Sr/Y (Sr/Y average  = 79) and high La/Yb (La/Yb average  = 56) ratios, and strongly fractionated (La n /Yb n  = 9–69) REE patterns. Their moderate Ni (Ni average  = 50 ppm), Cr (Cr average  = 85 ppm), variable Cr/Ni ratio (0.65–3.56) and low TiO 2 (TiO 2average  = 0.5 wt%) indicate little to no interaction with the peridotitic mantle. For most major elements (Al 2 O 3 , FeO t , Na 2 O, TiO 2 and P 2 O 5 ) the monzonite and the diorite suites display subparallel trends for the same SiO 2 content indicating they represent distinct melts. Intrusions belonging to the diorite suite have high Na 2 O (Na 2 O average  = 4.2 wt%), Dy/Yb n (Dy/Yb n-average  = 1.6), a positive Sr anomaly and uncorrelated Nb/La and Zr/Sm ratios suggesting derivation from partial melting of garnet-bearing amphibolite. Intrusions belonging to the monzonite suite have higher Na 2 O (Na2O average  = 5.61 wt%), Dy/Yb n (Dy/Yb n-average  = 2.21), a negative Sr anomaly and correlated Nb/La and Zr/Sm ratios consistent with derivation from partial melting of eclogite with residual rutile. Small variations in the Th/U ratio and near chondritic/MORB average values (Th/U monzonite  = 3.65; Th/U diorite  = 2.92) are inconsistent with a subducting slab signature, and it is proposed that the monzonite and the diorite suites of the KIC formed by partial melting of garnet-bearing, lower mafic crust of an oceanic plateau. The granodiorite suite has lower Mg# (Mg# average  = 41), moderately fractionated REE, low Sr/Y (Sr/Y average  = 20), La/Yb (La/Yb average  = 15), Dy/Yb n (DyYb n-average  = 1.24) and small negative Eu anomalies suggesting derivation from partial melting of amphibolite and plagioclase fractionation. Near-MORB Th/U (Th/U average  = 2.92) and Zr/Sm (Zr/Sm average  = 30.21) ratios are consistent with intracrustal melting of amphibolite. Archean rocks with an “adakitic” geochemical signature have been used to argue in favour of a plate tectonics regime in the Archean. The results presented here suggest that tectonic models for the Tanzania Craton, which invoke a subduction-related setting for all greenstone belts may need revision. [ABSTRACT FROM AUTHOR]

For the Permian-Triassic foidite and meimechite lavas of Polar Siberia, both the whole-rock petrochemistry and geochemistry and that of melt inclusions in olivine phenocrysts from the same rocks have been demonstrated to be similar. In addition, their isotope characteristics imply the possibility of their generation from an abyssal parental melt compositionally resembling a high-Mg alkaline picrite. [ABSTRACT FROM AUTHOR]

Small eruptive centres commonly have more primitive lavas than those associated with stratovolcanoes, an observation that has been taken to indicate a short magma residence in the crust relative to those reservoirs below stratovolcanoes. The Caburgua cones of the Andean Southern Volcanic Zone from a basaltic small eruptive centre where this can be tested. Here, we use MELTS simulations, and the available thermobarometry data to determine the conditions of olivine crystal rim formation and the Mg-Fe diffusion modelling to determine the magma residence times of those rims in the crust. Results yield timescales varying from a few days to dozens of days, and if freezing is to be avoided, can only be explained by some form of storage or slow transport through at least one shallow magma body. The longest durations of magma residence seen in the olivine rim zones are up to 471 days. These timescales are shorter than those estimated (decadal) from the nearby, more-differentiated, and well-established stratovolcano, Villarrica, which has a dominantly basaltic andesite composition. For Caburgua cones, we propose the existence of a transient reservoir, in contrast to a long-lived reservoir such as that inferred beneath the adjacent Villarrica stratovolcano. [ABSTRACT FROM AUTHOR]

A noticeable characteristic of the Sanandaj-Sirjan zone (SSZ) of Iran is the presence of extensive mafic to felsic intrusive igneous rocks in the host metamorphic rocks of Palaeozoic and Mesozoic eras. A similar composition is evident in batholithic size Khunrang Instrusive Complex (KIC) of southern SSZ. The rocks that make the KIC complex are mostly leucocratic microdiorite, quartz diorite, tonalite, granodiorite, granite and subordinate mesocratic to melanocratic pyroxene hornblende-gabbro and microgabbro. Field evidence and geochemical data suggest that the felsic rocks are not the products of fractional crystallization from a mafic phase. Using various discrimination and normalized multi-element diagrams suggest that mafic rocks, of tholeiitic to calc-alkaline affinities, were formed in an island arc or continental arc setting, from a metasomatized lithospheric mantle, above the stability field of garnet in a subduction zone environment. The felsic rocks, calc-alkaline and metaluminous in nature, have I-type granite characteristics. Their relative enrichment in large ion lithophile elements (LILEs) such as Ba, Cs and K and depletion in high field strength elements (HFSEs) such as Nb, Ta and Ti, is a signature of their development in an arc related environment in an active continental margin, similar to KIC mafic rocks. Geochemical characteristics suggest that the KIC felsic rocks were formed by partial melting of metabasic rocks of lower crust in response to underplating of mantle-derived basaltic magmas in an active continental margin as a result of Neo-Tethys oceanic crust subduction beneath the Central Iranian microcontinent in Mesozoic time. [ABSTRACT FROM AUTHOR]

Bauxite deposits, traditionally the main source of aluminum, have been recently targeted for their remarkable contents in rare earth elements (REE). With ∑REE (lanthanoids + Sc + Y) concentrations systematically higher than ∼1400 ppm (av. = 1530 ppm), the Las Mercedes karstic bauxites in the Dominican Republic rank as one of the REE-richest deposits of its style. The bauxitic ore in the Las Mercedes deposit is mostly unlithified and has a homogeneous-massive lithostructure, with only local cross-stratification and graded bedding. The dominant arenaceous and round-grained texture is composed of bauxite particles and subordinate ooids, pisoids and carbonate clasts. Mineralogically, the bauxite ore is composed mostly of gibbsite and lesser amounts of kaolinite, hematite, boehmite, anatase, goethite, chromian spinel and zircon. Identified REE-minerals include cerianite and monazite-Ce, whose composition accounts for the steady enrichment in light- relative to medium- and heavy-REE of the studied bauxites. Considering the paleo-geomorphology of the study area, we propose that bauxites in the Las Mercedes deposit are the product of the erosion and deposition of lithified bauxites located at higher elevations in the Bahoruco ranges. Based on the available data, we suggest a mixed lithological source for the bauxite deposits at the district scale: bedrock carbonates and an igneous source of likely mafic composition. [ABSTRACT FROM AUTHOR]

The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. 87 Sr/ 86 Sr i = 0.7042–0.7044, 143 Nd/ 144 Nd i = 0.5128–0.5129, 206 Pb/ 204 Pb i = 18.90–18.94, εHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker [Ts/(Ts + Tm)] all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process. [ABSTRACT FROM AUTHOR]

Zircon U–Pb dating and whole-rock geochemical analysis have been performed on Late Jurassic – Early Cretaceous intrusive rocks of the Ulanhot area, NE China, with the aim of constraining the tectonic evolution of the central and southern Da Xingan Range. Zircon U–Pb dating indicates that Late Jurassic – Early Cretaceous magmatic events experienced four stages at: c. 155 Ma; c. 144 Ma; 135–130 Ma; and c. 126 Ma. The c. 155 Ma magmatic event consists of quartz diorite and granite-porphyryp with the geochemical characteristic of high Sr and Sr/Y or high A/CNK (1.38), implying the primary magma was derived from partial melting of a thickened lower crust which induced the closure of the Mongol–Okhotsk Ocean. The c. 144 Ma magmatic event consists of quartz monzodiorite with the geochemical characteristics of alkaline series, and indicates the delamination of a thickened crust. The 135–130 Ma magmatic event consists of syenogranite and granite-porphyry with characteristics of both I-type and A-type granites, which induced both the subduction of the Palaeo-Pacific oceanic plate and the post-orogenic extension of the Mongol–Okhotsk Orogenic Belt. The c. 126 Ma magmatic event consisted of highly fractionated I-type biotite granite and alkaline series gabbro, marking the end of the Mongol–Okhotsk Orogen, and implying that the study area was controlled by the circum-Pacific tectonic system during this stage. [ABSTRACT FROM AUTHOR]

This work presents new data on the conditions of formation of igneous rocks on the western slope of the Southern Urals and the adjacent part of the East European Platform. Based on the calculated P-T melting parameters of the mantle substrate, it is shown that plume magmatism leads to the formation of similar rocks (picrites and picrite-dolerites), while the genesis of them is quite different. The first type of rocks is a product of crystallization of the undifferentiated mantle-derived melt in the upper horizons of the crust; the rocks of the second type are formed as a result of magma differentiation in large intracrustal magma chambers. [ABSTRACT FROM AUTHOR]

This study presents the preliminary results of 222Rn (radon) and 220Rn (thoron) concentrations that were measured in the soils developed on igneous rocks including mafic (pillow lavas, basalts and melaphyre) and acid (keratophyre, rhyolite and rhyolitic tuff) rocks at ten locations in the Kaczawa Mountains (SW Poland). The measurements were carried out at sampling depths of 10, 40 and 80 cm using a RAD7 portable radon system. The highest concentrations of radon (222Rn) were mainly observed in the soils overlaying acid igneous rocks. The highest value of 11 kBq m-3 was obtained at a depth of 10 cm for soils overlaying melaphyre. At depths of 40 and 80 cm, the averages of 222Rn concentrations showed the same values of 3.6 kBq m-3 for all of the soils investigated. The highest concentrations of thoron (220Rn) were observed in soils overlaying acid igneous rocks, i.e. the value of 49 kBq m-3 at a depth of 40 cm for soils overlaying rhyolitic tuff. In the soils developed on basalts, the average concentrations of 222Rn increased with the sampling depth, whereas the average concentrations of thoron (220Rn) decreased with increasing sampling depth. Positive correlations were found between 232Th activity in the parent rocks and soil gas 220Rn concentrations at all of the sampling depths, whereas a positive correlation between soil gas 222Rn and the 238U activity concentration in the parent rocks was only found at a depth of 40 cm. [ABSTRACT FROM AUTHOR]

U-Pb geochronological studies of igneous rocks of the Crimean Mountains were carried out for the first time. The ages of magma crystallization determined for gabbro-dolerites of the Dzhidair and Pervomaiskii intrusions point to the injection of these rocks during the Middle Jurassic Aalenian-Bajocian stage of magmatism. The Berriasian-Valanginian and Aptian age of sill-like bodies within the mass of volcanogenic-sedimentary rocks presumes the necessity to reconsider the common notion of an exclusively Albian magmatic event during the Cretaceous. High-precision U-Pb dating of magma intrusions allowed us to verify the age of Middle Jurassic magmatism and to distinguish the new Early Cretaceous Berriasian-Valanginian magmatism stage of basic composition. [ABSTRACT FROM AUTHOR]

According to isotopic analysis of rocks of the Reft gabbro-diorite-tonalite complex (Middle Urals), gabbro and related diorite and dikes and vein-shaped bodies of plagiogranitoids, crosscutting gabbro, are similar to the depleted mantle substance in ε( T) = 8.6-9.7 and ε( T) = 15.9-17.9. Their model Hf ages are correlated with the time of crystallization. Here, the tonalites and quartz diorites constituting most of the Reft massif are characterized by lower values: ε( T) = 3.7-6.0, ε( T) = 11.1-12.7, and T values significantly exceeding the age datings. This is evidence that Neoproterozoic crustal rocks were a source of parental magma for these rocks. The primary Sr/Sr ratio in rocks of both groups is highly variable (0.70348-0.70495). The data obtained allow us to reach the conclusion that the Reft gabbro-diorite-tonalite complex was formed as a result of nearly synchronous processes occurring in the crust and the mantle within a limited area. [ABSTRACT FROM AUTHOR]

The Basu metamorphic complex, surrounded by ophiolitic melanges and intruded by a large volume of undeformed granitoid rocks along the eastern segment of the Bangong-Nujiang suture, holds one of the keys to understanding the pre-Cenozoic tectonic evolution of central Tibet. Zircon U-Pb dating of rocks from the Basu metamorphic complex reveals that meta-igneous rocks yield Early Paleozoic crystallization ages of 500–492 Ma and an Early Jurassic metamorphic age of ~ 173 Ma, and that undeformed granitoid rocks yield crystallization ages of approximately 186–174 Ma. Whole rock geochemical and zircon Lu-Hf isotopic data indicate that the undeformed granitoid rocks originated mainly from partial melting of ancient crustal sources, which may reflect a collisional orogenic setting. 40 Ar/ 39 Ar dating of biotite from a sillimanite-garnet-biotite paragneiss shows cooling to 300 ± 50 °C at ~ 165 Ma. These data indicate significant Early Jurassic tectonism, during which most of the Basu metamorphic complex was formed. Furthermore, the age data resemble those of the Amdo metamorphic complex located approximately 500 km to the west along the Bangong-Nujiang suture. Together, these complexes may represent a “destroyed or unrecognized” block, i.e., the Amdo-Tongka block, which may be the eastern extension of the South Qiangtang terrane. Based on the tectonic outlines of the multiple ophiolitic zones and magmatic belts, we suggest a new archipelago-accretion model that attributes the Early Jurassic tectonism to an arc-continent/micro-continent collision. This model further enables the reconstruction of the eastern Tethyan Ocean and the orogenic processes of central Tibet during the Mesozoic. [ABSTRACT FROM AUTHOR]

Gray cast iron is the most commonly used material in automobile brake rotors. It generates heat easily during braking which affects its mechanical properties and the Coefficient of friction varies depending on the type of material used for the brake rotor. Aluminium (Al) based metal matrix composite can be an efficient and effective braking material compared to cast iron and matrix alloy. In the present investigation, Al6082 composites were fabricated by stir casting method by varying weight percentage of reinforcements for Sample1 (Al 90% + SiC 10%), Sample 2 (Al 90% + SiC 5% + fly ash 5%) and Sample 3 (Al 90% + SiC 5% + basalt 5%). Chemical compositions, micro hardness, wear test and tensile test were performed to study the mechanical behavior of all the test specimens. The surface morphology was studied using microscopic inspection to indicate the distribution of reinforcement particles and bonding between the matrixes. Composites containing hard oxides (like SiC) are preferred for high wear resistance along with increased hardness and high temperature oxidation resistance. The result reveals that wear rates of the composite materials is lower than that of the matrix alloy and friction coefficient was minimum. Also, it improves the micro hardness and tensile strength. The addition of fly ash and basalt decreases the wear and it acquired density almost three times lower than that of gray cast iron. In this investigation, the alternate materials for automobile brake rotors with Al reinforced composites were studied. [ABSTRACT FROM AUTHOR]

The Gangdese batholith, more than 2500 km in length, is composed mainly of Jurassic-Miocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place for study of Neo-Tethyan ocean geodynamic evolution and plateau uplift. Recent studies on the Gangdese Jurassic felsic magmatism highlight its juvenile source. However, important aspects concerning the genesis of the juvenile magmatism and related deep geodynamic evolution are still unclear. Here, we report detailed petrological, geochronological, geochemical, whole-rock Sr-Nd isotopic, and in situ Sr-Hf isotopic data for a recently identified hornblende gabbro in the Dongga area, southern Lhasa sub-block. This hornblende gabbro is dominated by hornblende and plagioclase, dated at Early Jurassic (ca. 180-190 Ma), and characterized by a narrow compositional range in SiO2 (49.38wt%-52.27wt%), MgO (4.08wt%-7.00wt%), FeO (10.43wt%-11.77wt%), Na2O (2.58wt%-3.51wt%), and K2O (0.48wt%-1.53wt%). It has depleted isotopic signatures, with whole-rock (87Sr/86Sr)i ratios of 0.7033-0.7043, εNd( t) values of +4.90 to +6.99, in situ plagioclase (87Sr/86Sr)i ratios of 0.7034-0.7042, and zircon εHf( t) of +12.2 to +16.8. Our results integrated with published data suggest a model of Gangdese juvenile crustal growth by a subduction-related water-enriched mantle wedge. The hydrous partial melting of the lithosphere mantle was triggered by the dehydration of a Neo-Tethyan oceanic slab. This mafic magmatism emplaced in the middle-lower crust of intraoceanic arcs or active continental margins, leading to Jurassic juvenile crustal growth in southern Tibet. [ABSTRACT FROM AUTHOR]

The Alnö complex in central Sweden is one of the largest alkaline and carbonatite ring-shaped intrusions in the world. Presented here is the 3D inversion of ground gravity and aeromagnetic data that confirms some of the previous ideas about the 3D geometry of the complex but also suggests that the complex may continue laterally further to north than earlier expected. The gravity and aeromagnetic data show the complex as (i) a strong positiver Bouguer anomaly, around 20 mGal, one of the strongest gravity gradients observed in Sweden, and (ii) a strong positive magnetic anomaly, exceeding 2000 nT. Magnetic structures are clearly discernible within the complex and surrounding area. Petrophysical measurements (density, bulk magnetic susceptibility, and magnetic remanence) were used to constrain the 3D inversion. Both gravity and magnetic inversion models suggest that dense (> 2850 kg/m3) and magnetic (> 0.05 SI) rocks extend down to about 3.5–4 km depth. Previous studies have suggested a solidified magma reservoir at this approximate depth. The inversion models further suggest that two apparently separate regions within the intrusion with gravity and magnetic highs are likely connected at depth, starting from 800–1000 m, implying a common source for the rocks observed in these two regions. The modelling of the aeromagnetic data indicates that a more than 3 km wide ring-shaped magnetic high in the bay that can be a hidden part of the complex, linking a satellite intrusion in Söråker on the northern side of the bay to the main intrusion on the Alnö Island. While the rim of the ring must consist of highly susceptible rocks to support the magnetic anomaly, the centre has a relatively low magnetisation and is probably made up of low-susceptible wall-rocks or metasomatised wall-rocks down to about 2 km. Below this depth the 3D susceptibility model shows higher magnetic susceptibility values. From these observations the solidified magma chamber is interpreted to extend further to north than has previously been suggested. [ABSTRACT FROM AUTHOR]

The noble metal (PGE and Au) geochemical specialization of igneous rocks of the Bashkir meganticlinorium and adjacent areas of the East European Platform is characterized for the first time. The identical plots of normalized PGE and Au concentrations of igneous rocks in these regions indicate similar conditions and mechanisms of the formation of the noble metal geochemical specialization during the emplacement of magmatic bodies. It is established that a specific feature of noble metal geochemical specialization (the 'rhodium anomaly') in magmatic complexes of the Bashkir meganticlinorium and eastern areas of the East European Platform is determined by the concentrations of noble metals in sulfide minerals (pentlandite); i.e., it is 'primary' in origin. [ABSTRACT FROM AUTHOR]

Minerals can be liberated by random fracture of particles into smaller fragments or by detachment along phase boundaries. These two mechanisms represent borderline cases. When ores get comminuted the liberation of minerals is achieved to some extent by both mechanisms. This article describes a method to determine the extent of transgranular and intergranular fracture based on 2-dimensional analysis of surface exposure of minerals. The approach uses the unbiased surface information of phase specific surface area ( PSSA ), phase specific free surface ( PSFS ) and phase specific interfacial area ( PSIA ) of minerals and their change with comminution. The parameters are discussed related to the normalized grain size, which is the ratio of mineral grain size in the product to mineral grain size in the unbroken material. Finally, the amount of transgranular and intergranular fracture on surface exposure can be calculated using the phase specific surface parameters. A sedimentary rock (apatite ore), an igneous rock (nepheline-syenite) and an artificial material (copper slags) were ground to different fineness. Based on the mineral liberation analysis (MLA) of feed and products, the extent of phase boundary fracture on the surface exposure of the minerals is studied. [ABSTRACT FROM AUTHOR]

A circular structure, termed as cauldron of volcanic origin, was located near Mohar village in Shivpuri district (M.P.) in the year 2000. Subsequently, the same structure was called as Dhala structure of impact origin. There may be debate over the origin and evolution of this circular structure, but it is characterized by a unique lithological set-up within the Bundelkhand craton. The circular structure is defined by annular disposition of igneous and sedimentary rocks. This includes a set of felsic volcanic rocks and associated breccias named as Mohar Formation, exposed in the outer rim of the circular structure. The inner part of the circular structure has sedimentary sequence, termed as Dhala Formation. The field relations indicate that the Mohar and Dhala foarmations are younger than Bundelkhand granitoid complex but older than Kaimur Group. This period in Indian stratigraphy corresponds to Semri Group which consists of Porcellanite Formation, the rocks of which have formed due to deposition of volcanic ash. The geochronological data and field relations between different litho-units indicate that the Mohar volcanism which generated large volume of volcanic ash was a possible source for the formation of Porcellanite Formation. The deposition of sedimentary sequence in main Vindhyan basin was continued, whereas the volcanic activity in Mohar area continued till H ≈ 1.0 Ga. Since, acid volcanic activity has been reported in different parts of the world at H ≈ 1.0 Ga., it is possible that the Mohar acid volcanic activity is not an isolated event; instead it may be a part of global volcanic activities around H ≈ 1.0 Ga. [ABSTRACT FROM AUTHOR]

The Bashisuogong (BSSG) complex is located in the tectonic transition zone between South Tianshan Collisional Belt (STCB) and Tarim Block (TB). The complex is composed of a mafic unit (mainly including gabbro and diabase) and a felsic unit (mainly composed of quartz syenite and alkali granite), both of which are crosscut by several diabase and alkali granite dykes. Here we present LA-ICP-MS zircon U–Pb data which show that the two units were emplaced coevally at ~ 276 Ma. The rocks from the two units display a wide SiO 2 gap, implying a typical bimodal magmatic feature. The petrographic and geochemical evidence such as mafic microgranular enclave (MME) within the syenite, negative linear correlations between SiO 2 and some major elements, and a wide range of ( 87 Sr/ 86 Sr) i suggest that the syenite formed via magma mixing process. The positive ε Nd (t) values (+ 5.42 to + 5.66 for gabbro and + 4.70 to + 5.02 for diabase) and OIB-like geochemical features of the mafic unit indicate that the parent magma was derived from asthenospheric mantle or mantle plume. The felsic unit shows higher contents of SiO 2 , K 2 O and total alkalis. Their trace element patterns are characterized by Rb, Y, Zr and Hf enrichment, and high 10,000 Ga/Al ratios, indicating an A1-type affinity. The syenite shows ε Nd (t) values in the range of − 0.15 to + 0.30 and zircon ε Hf (t) values of + 1.68 to + 5.10, whereas the alkali granite has ε Nd (t) values of − 2.10 to − 1.92 and ε Hf (t) values of − 4.10 to + 0.32. The two stage Hf isotope model ages of zircon grains in the syenite are older than 1.0 Ga, whereas those of the alkali granite are even older (> 1.3 Ga). Our results suggest that the alkali granite was generated by partial melting of a Neoproterozoic gabbroic source. Zircon grains in the A1-type felsic intrusions yield high Zr saturation temperature (728–983 °C). Although the OIB-like affinities and high temperature zircon grains of the BSSG complex suggest a genetic link with the Tarim mantle plume, considering the Late Carboniferous–Early Permian A-type granites commonly occurring in the STCB, Altay and circum-Junggar region as narrow linear belts, we correlate the magmatism with post-collisional setting rather than a mantle plume event. The effect of Tarim mantle plume might not have reached beyond the north of Tianshan. [ABSTRACT FROM AUTHOR]

A layered gabbro suite was emplaced around Kuliana (lat 22°3ʹN and long 86°38ʹE), Orissa, eastern India, within deformed metasedimentary rocks of the north Singhbhum mobile belt. This magmatic suite does not have any exposures of feeder dikes, chilled margins, or other evidence for an intrusive character. Because the cumulate layers do not provide information about the parent magma of this suite, the equilibrium distribution method has been utilized in this study to estimate trace element concentrations of melts in equilibrium with the cumulate solid products. The mineralogical and chemical evolution of the layered suite has been carried out on the basis of both calculated parent magmas and chemical data of cumulate layers. The magmatic differentiation of the layered suite was guided by fractional crystallization and punctuated by an event of magma chamber replenishment. The calculated parent melts exhibit enriched light rare earth elements and large ion lithophile elements, marked depletion of Ti and Y, and successive total rare earth element depletion through progressive differentiation. Plotting several immobile trace element diagrams—Nb/Yb versus Th/Yb, La/Nb versus Th/Nb, Nb/La versus Ba/La, and Zr versus Zr/Y— reveals their chemical affinity to enriched mid-ocean ridge basalt–like magmas. The La versus La/Sm plot of mantle sources affected by partial melting shows a relatively low degree (8%–30%) of melting and indicates a deeper (garnet facies) mantle as the possible source region of the parent magmas of the Kuliana layered mafic suite. [ABSTRACT FROM AUTHOR]

A large number of published accounts are available on the metamorphic evolution of the Central Zone of the Limpopo Belt. However, most investigations on the P-T evolution of this zone are restricted to pelitic and calcsilicate rocks. In this paper we present for the first time a detailed mineralogical and petrological investigation on an ultramafic granulite of komatiitic composition, which occurs in the vicinity of Musina in the Central Zone. These rocks are composed mainly of magnesium-rich Ca-amphibole (pargasite: MgO up to 18 wt%), together with Mg-rich olivine (XMg = 0.82 to 0.83) and orthopyroxene (XMg = 0.82 to 0.84), Cr-rich spinel, magnetite and some sulfide minerals. This set of minerals represents the peak metamorphic assemblage formed during the early stage of the metamorphic evolution of the Central Zone and is different from the mineral assemblage of less altered komatiites. This assemblage was subjected to minor retrogression and alteration to chlorite and serpentine during the waning stage of the metamorphic evolution of the Central Zone. Thermodynamic calculations combining classical conventional methods as well as equilibrium assemblage modelling using Theriak-Domino, in conjunction with textural relationships and mineral chemistry, indicate that the studied rocks went through granulite facies metamorphic conditions at a temperature of up to 820°C and an intermediate pressure of up to 8.5 kbar. These P-T conditions are in good agreement with previous investigations of metamorphic conditions on other rock types (mainly metapelites) in the Central Zone of the Limpopo Belt. [ABSTRACT FROM AUTHOR]

The Permian Hulu Ni-Cu sulfide deposit is located at the southern margin of the Central Asian Orogenic Belt (CAOB) in Northern Xinjiang, Northwestern China. The host intrusion of the Hulu deposit is composed of a layered mafic-ultramafic sequence and a dike-like unit. The layered sequence is composed of harzburgite, lherzolite, pyroxenite, gabbro, gabbrodiorite and diorite. The dike-like body comprises lherzolite and gabbro. Sulfide orebodies occur mainly within the harzburgite, pyroxenite and lherzolite at the base of the layered sequence and within the lherzolite in the dike-like body. Sulfide mineralization from the Hulu deposit shows significant depletion of PGE relative to Cu and Ni. These elements show good positive correlations with S in the sulfide mineralization from the dike-like unit but relatively weak correlations in the sulfide mineralization from the layered sequence. The sulfide mineralization from the layered unit shows excellent positive correlations between Ir and Os, Ru or Rh, and poor relationships between Ir and Pt or Pd. On the contrary, sulfide mineralization from the dike-like unit shows good correlations in the diagrams of Os, Ru, Rh, Pt and Pd against Ir. Both high Cu/Pd ratios (8855–481,398) and our modeling indicate that PGE depletion resulted from sulfide removal in a deep staging magma chamber. The evolved PGE-depleted magmas then ascended to the shallower magma chamber and became sulfide saturation due to crustal contamination. Both low Se/S ratios (33.5 × 10 −6 –487.5 × 10 −6 ) and a negative correlation between Se/S and Cu/Pd ratios are consistent with the addition of crustal S. A large number of sulfide liquids segregated with minor crystallization of monosulfide solid solution (MSS) in the shallower magma chamber. When new magma pulses with unfractionated sulfide droplets entered the shallower magma chamber, the sulfide slurry containing crystallized MSS may be disrupted and mixed with the unfractionated sulfide droplets. The mixing of sulfides would result in poor correlations between IPGE (Os, Ir and Ru) and PPGE (Rh, Pt and Pd) in the layered sequence. By contrast, insufficient mixing of the sulfide droplets segregated from different pulses of magma led to variable PGE tenors and good correlations between IPGE and PPGE in the dike-like unit. Numerous Permian mafic-ultramafic intrusions in the CAOB are favorable hosts to magmatic sulfide deposits. [ABSTRACT FROM AUTHOR]

Geochemical study of the metamorphosed pillow lavas of the Chara Zone revealed that their protoliths have N-MORB compositions. Elevated concentrations of K, Rb, Cs, and lower Ca may be related not to blueschist metamorphism, but rather they may be inherited from underwater alteration of parental basalts. Comparative analysis of the compositions of massive glaucophanites and vein rocks demonstrated the relative mobility of Sr, U, P, Ba, Rb, K, Cs, Ca, and LREEs, at least on the local scale. Their mobility has been provided by fluids circulating in the subduction zone, where the fluids have been generated through slab dehydratation processes. These studies of metamorphosed pillow lavas of the Chara Zone displayed only local alterations in the bulk composition of their protoliths, which evidences a low intensity of fluid flows: this allowed preservation of the geochemistry of oceanic basalts. [ABSTRACT FROM AUTHOR]

U-Pb analysis of zircons from igneous rocks in the Elashan Mountain, easternmost segment of the East Kunlun Orogen yielded 252-232 Ma. Geochemically, these rocks are mainly high in SiO2, K2O and K2O+Na2O contents, low in P2O5 and TiO2 contents, depleted in Ba, Sr, P, Ti and enriched in U, Hf, Zr, showing features of I-type granite. The zircon εHf( t) values of the Early Triassic Jiamuge'er rhyolite porphyry (252±3 Ma) are positive (+1.6 to +12.1), suggesting a juvenile crustal source mixing with little old crustal component, and the zircon εHf( t) values of the Middle Triassic Manzhang'gang granodiorite (244±3 Ma) and Dehailong diorite (237+3 Ma) are predominately negative (−8.4 to +1.0), indicating an older crustal source. In comparison, the zircon εHf( t) values of the Late Triassic syenogranites from Suigen'ergang (234±2Ma), Ge'ermugang (233±2 Ma) and Yue'ergen (232±3 Ma) plutons vary from −3.8 to +5.0, suggesting a crust-mantle mixing source. From Early-Middle Triassic (252-237 Ma) to Late Triassic (234-232 Ma), the geochemical characteristics of these rocks show the change from a subduction-collision setting to a post-collision or within-plate setting. By comparing of these new age data with 77 zircon U-Pb ages of igneous rocks of the eastern part of East Kunlun orogen from published literatures, we conclude that the igneous rocks of Elashan Mountain and these of the eastern part of East Kunlun Orogen belong to one magmatic belt. All these data indicate that the Triassic magmatic events of the eastern part of East Kunlun Orogen can be divided into three stages: 252-238 Ma, 238-226 Ma and 226-212 Ma. Statistically, the average εHf( t) values of the three-stage igneous rocks show a tendency, from the old to young, from -0.75±0.25 to lower -2.65±0.52 and then to -1.22±0.25, respectively, which reveal the change of their sources. These characteristics can be explained as a crust-mantle mixing source generated in a subductional stage, mainly crust source in a syn-collisional stage and a crust-mantle mixing source (lower crust with mantle-derived underplating magma) in a post-collisional stage. The identification of these three magmatic events in the Elashan Mountain, including all the eastern part of East Kunlun Orogen, provides new evidence for better understanding of the tectonic evolution of the northward subduction and closure of the Paleo-Tethyan (252-238 Ma), the collision of the Songpan-Ganzi block with the southern margin of Qaidam block (238-226 Ma), and the post-collisional setting (226-212 Ma) during the Early Mesozoic period. [ABSTRACT FROM AUTHOR]

In this article we present geochemical and isotope characteristics of rocks of the Unerikan, Selitkan and Aezop-Yamalin volcano-plutonic zones of the eastern termination of the Mongol-Okhotsk Orogenic Belt. The obtained data demonstrate that the Mesozoic igneous rocks of the Mongol-Okhotsk sector of the Pacific Folded Belt were formed due to the melting of the continental crust in a tectonic setting corresponding to a suprasubduction one. [ABSTRACT FROM AUTHOR]

A low-dilution, undersized (12.5 mm diameter) glass–bead technique was developed for X-ray fluorescence determination of 34 components (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Hf,W, and Pb) in precious silicic samples for geochemistry and archeology. This preparation was consolidated based on the properties of the specimen, including disk formability and detachability from a small crucible, through variation of the amounts of the two samples (basaltic and granitic rocks) and releasing reagent. The specimen was prepared by fusing a mixture of 200 mg of powdered sample, 200 mg of lithium tetraborate as a flux, and 60 μl of 18.42 mass% lithium chloride solution as a releasing agent in a small platinum crucible. Calibration curves were drawn using synthetic calibration standards, which were prepared by compounding chemical reagents, such as oxides, carbonates, and diphosphates containing analytes. The calibration curves showed good linearity with correlation coefficient values greater than 0.990. Using the proposed method, we determined 34 components in five igneous rock reference samples. The results were in agreement with the recommended values, accounting for uncertainties. With this method, preparation requires only small amounts of the powdered sample and alkali flux; however, still allowing for determination of many analytes, which is advantageous when dealing with limited quantities of precious samples. The present method has potential applications in the chemical characterization of various geological and archeological samples. [ABSTRACT FROM AUTHOR]

The Moretown Formation, exposed as a north-trending unit that extends from northern Vermont to Connecticut, is located along a critical Appalachian litho-tectonic zone between the paleomargin of Laurentia and accreted oceanic terranes. Remnants of magmatic activity, in part preserved as metamorphosed mafic rocks in the Moretown Formation and the overlying Cram Hill Formation, are a key to further understanding the tectonic history of the northern Appalachians. Field relationships suggest that the metamorphosed mafic rocks might have formed during and after Taconian deformation, which occurred at ca. 470 to 460 Ma. Geochemistry indicates that the sampled metamorphosed mafic rocks were mostly basalts or basaltic andesites. The rocks have moderate TiO2 contents (1-2.5 wt %), are slightly enriched in the light-rare earth elements relative to the heavy rare earths, and have negative Nb-Ta anomalies in MORB-normalized extended rare earth element diagrams. Their chemistry is similar to compositions of basalts from western Pacific extensional basins near volcanic arcs. The metamorphosed mafic rocks o f this study are similar in chemistry to both the pre-Silurian Mount Norris Intrusive Suite o f northern Vermont, and also to some o f Late Silurian rocks within the Lake Memphremagog Intrusive Suite, particularly the Comerford Intrusive Complex of Vermont and New Hampshire. Both suites may be represented among the samples of this study. The geochemistry of all samples indicates that parental magmas were generated in supra-subduction extensional environments during lithospheric delamination. [ABSTRACT FROM AUTHOR]

Mantle-derived carbonatites are igneous rocks dominated by carbonate minerals. Intrusive carbonatites typically contain calcite and, less commonly, dolomite and siderite as the only carbonate minerals. In contrast, lavas erupted by the only active carbonatite volcano on Earth, Oldoinyo Lengai, Tanzania, are enriched in Na-rich carbonate phenocrysts (nyerereite and gregoryite) and Na-K halides in the groundmass. The apparent paradox between the compositions of intrusive and extrusive carbonatites has not been satisfactorily resolved. This study records the fortuitous preservation of halite in the intrusive dolomitic carbonatite of the St.-Honoré carbonatite complex (Québec, Canada), more than 490 m below the present surface. Halite occurs intergrown with, and included in, magmatic minerals typical of intrusive carbonatites; i.e., dolomite, calcite, apatite, rare earth element fluorocarbonates, pyrochlore, fluorite, and phlogopite. Halite is also a major daughter phase of melt inclusions hosted in early magmatic minerals, apatite and pyrochlore. The carbon isotope composition of dolomite (δ13C = -5.2‰) and Sr-Nd isotope compositions of individual minerals (87Sr/86Sri = 0.70287 in apatite, to 0.70443 in halite; εNd = +3.2 to +4.0) indicate a mantle origin for the St.-Honoré carbonatite parental melt. More radiogenic Sr compositions of dolomite and dolomite-hosted halite and heavy oxygen isotope composition of dolomite (δ18O = +23‰) suggest their formation at some time after magma emplacement by recrystallization of original magmatic components in the presence of ambient fluids. Our observations indicate that water-soluble chloride minerals, common in the modern natrocarbonatite lavas, can be significant but ephemeral components of intrusive carbonatite complexes. We therefore infer that the parental magmas that produce primary carbonatite melts might be enriched in Na and Cl. This conclusion affects existing models for mantle source compositions, melting scenarios, temperature, rheological properties, and crystallization path of carbonatite melts. [ABSTRACT FROM AUTHOR]

The lower layered nepheline syenite sequence (kakortokites) of the Mesoproterozoic alkaline to peralkaline Ilímaussaq complex, South Greenland shows spectacular rhythmic meter-scale igneous layering. The 29 exposed units have sharp contacts against each other and each of these units consists of three modally graded layers dominated by arfvedsonitic amphibole, eudialyte-group minerals, and alkali feldspar, respectively. This study uses field observations on changes in mineral orientation, recurrent mineral textures, compositional data from eudialyte-group minerals and amphibole, and settling rate calculations based on a modified Stokes' equation to explain the igneous layering of the kakortokites. We propose that the three major cumulus minerals (amphibole, eudialyte s.l., and alkali feldspar) were separated from each other by density contrasts, resulting in modally graded layers within each unit. The densest of these three minerals (amphibole) formed crystal mats within the cooling magma body. These crystal mats acted as barriers that inhibited large-scale vertical migration of melts and crystals with increasing effectiveness over time. The sub-volumes of magma captured in between the crystal mats evolved largely as geochemically independent sub-systems, as indicated by the observed trends in mineral composition. [ABSTRACT FROM AUTHOR]