Basaltic Slab Research Articles

Determination of technical characteristics of traditional foam concrete and foam concrete with mineral fiber

Foam concrete is currently enjoying its popularity due to a number of advantages, such as non-toxicity, reduction of thermal insulation costs, noise absorption. Nowadays at the state level the issue of utilisation of waste of different nature and increasing the quality of recycling is constantly being considered. Also a big task is set in the scientific sphere of the country on recycling of utilised waste in different sectors and especially in the construction sector. There are numerous grant programmes in the scientific field, which are aimed at the use of waste in the industrial and construction sector of the country. This paper is devoted to the study of the qualitative characteristics of traditional foam concrete and foam concrete with the addition of mineral fibre. In the construction sphere the main thermal insulating material in the form of mineral boards is widely used and there are factories for the production of basalt boards in the course of production of which there is a lot of basalt waste. Tests have been carried out according to the standard methodology in order to determine the strength and density of the finished product. According to the test results it was determined that the pore structure and strength is uniform over the whole surface of the blocks. It was also determined that the specimens with fibre showed a strength of more than 50% compared to conventional foamed concrete. This work will be a good direction for further in-depth study on the utilisation of basalt slabs in construction.

Petrological, geochemical and geochronological evolution of massif type charnockite from the Eastern Ghats Province, India: Implications on the regional tectonics of the Rayner-Eastern Ghats orogeny

Massif type charnockite was emplaced in the lower crust of the Eastern Ghats Province and is now exposed over a large geographic area. The rock shows clear evidence of magmatic emplacement in lower crustal metasedimentary rocks, which occur as enclaves within the charnockite. Textural data suggest the magma underwent subsolidus cooling and subsequently metamorphosed to granulite facies (up to ∼ 910 °C, 9 kbar). Geochemical data show that the charnockite magma had variable chemistry which was acquired by differentiation and possible crustal contamination. The rock shows both high- and low-SiO2 types, with weakly peraluminous to metaluminous characters. Trace and REE fractionation trends suggest the magma had calcic to calc-alkaline affinities and was emplaced in a continental arc type collisional setting. Theoretical modelling suggests that such a magma could be generated by melting of a hydrated basaltic slab under CO2-rich fluid. U-Pb analysis on oscillatory zoned zircon domains from eight samples yields crystallization ages for the magma. While the majority of the samples show crystallization ages within ca. 980–940 Ma (978 ± 16 Ma, 968 ± 22 Ma, 951 ± 9 Ma, 954 ± 8 Ma, 951 ± 13 Ma and 939 ± 27 Ma), two samples yield crystallization ages of 1002 ± 13 Ma and 1020 ± 16 Ma. This implies two-phase emplacement of the charnockite magma which can be correlated with the tectonometamorphic evolution of the province. While the earlier pulse of charnockite magmatism is broadly synchronous with the first cycle (M1) of metamorphism, the later pulse followed when the lower crust was still hot. The two pulses of charnockite magmatism are broadly synchronous with those of the Mawson charnockite of the Rayner Province, East Antarctica. It is argued that the charnockite magmatism in the combined Rayner-Eastern Ghats Province was extensive and resulted from arc-continent accretion and collision between the India and East Antarctica during ca. 1030–900 Ma.

Проект Йозефа Бойса «7000 дубов» как способ излечения от травм исторической памяти

The article is devoted to the project of Joseph Beuys “7000 oaks”. This project was created for the Documenta 7 in Kassel. It is the most ambitious project of the artist. In it, he proposed planting oaks on the way from Kassel to Russia. This project combines environmental, social and historical values. It seems relevant that the project also has a pacifist focus. The article also analyzes the installation “The End of the 20th Century”, which uses basalt slabs that were used in the “7000 Oaks”. Usually the “7000 Oaks” was considered from the environmental or social point of view. The article focuses on its historical context, since the circumstances of its creation between Germany and Russia, the post-war period and the taboo on the tragedy of the war make it possible to say that this was also relevant for that time. The scientific novelty of this study is an aspect of historical memory associated with the trauma of war.

The composition of subduction zone fluids and the origin of the trace element enrichment in arc magmas

The partitioning of major and trace elements between eclogite and aqueous fluids with variable salinity was studied at 700–800 °C and 4–6 GPa in piston cylinder and multi anvil experiments. Fluid compositions were determined using the diamond trap technique combined with laser ablation ICP-MS measurements in the frozen state. In addition to NaCl, SiO2 is the main solute in the fluids. The fluid/eclogite partition coefficients of the large ion lithophile elements (LILE), such as Rb, Cs, Sr, and Ba as well as those of the light rare earths (LREE), of Pb, and of U increase by up to three orders of magnitude with salinity. These elements will therefore be efficiently transported by saline fluids. On the other hand, typical high field strength elements, such as Ti, Nb, and Ta, are not mobilized even at high salinities. Increasing temperature and pressure gradually increases the partitioning into the fluid. In particular, Th is mobilized by silica-rich fluids at 6 GPa already at low salinities. We show that we can fully reproduce the trace element enrichment pattern of primitive arc basalts by adding a few percent of saline fluid (with 5–10 wt% Cl) released from the basaltic slab to the zone of melting in the mantle wedge. Assuming 2 wt% of rutile in the eclogite equilibrated with the saline fluid produces a negative Nb Ta anomaly that is larger than in most primitive arc basalts. Therefore, we conclude that the rutile fraction in the subducted eclogite below most arcs is likely < 1 wt%. In fact, saline fluids would even produce a noticeable negative Nb Ta anomaly without any rutile in the eclogite residue. Metasomatism by sediment melts alone, on the other hand, is unable to produce the enrichment pattern seen in arc basalts. We, therefore, conclude that at least for primitive arc basalts, the release of hydrous fluids from the basaltic part of the subducted slab is the trigger for melting and the main agent of trace element enrichment. The contribution of sediment melts to the petrogenesis of these magmas is likely negligible. In the supplementary material, we provide a “Subduction Calculator” in Excel format, which allows the calculation of the trace element abundance pattern in primitive arc basalts as function of fluid salinity, the amount of fluid released from the basaltic part of the subducted slab, the fluid fraction added to the source, and the degree of melting.

Petrogenesis of a rare Ediacaran tonalite–trondhjemite–granodiorite suite, Egypt, and implications for Neoproterozoic Gondwana assembly

AbstractMost tonalite–trondhjemite–granodiorite (TTG) suites are Archean–Palaeoproterozoic in age, but those of Neoproterozoic–Phanerozoic age are scarce. A rare Ediacaran high-Al TTG suite has been identified at the Fannani Igneous Complex (FIC) in the northern Arabian–Nubian Shield, which is essentially composed of amalgamated Neoproterozoic island-arc Pan-African composite terranes that contain several ophiolitic sutures. The FIC exhibits a wide range of SiO2, Al2O3, Sr and Zr, shows moderate rare earth element (REE) enrichment, and K, Ti, Nb, Y and heavy REE depletion. It is a subsolvus suite with clear orogenic affinities and strong arc-geochemical signatures. The precise U–Pb zircon thermal ionization mass spectrometry age obtained (607.4 ± 1.95 Ma) indicates oceanic subduction extended to late stages of the East African Orogeny. The FIC exhibits87Sr/86Sr compositions of 0.70346–0.71091 (Sr(i)ratio, 0.70284), and143Nd/144Nd of 0.51254–0.51270 (ϵNd(t) = +5.12 to +7.16), typical of modern oceanic-arc rocks (as Japan-arc basalts), and suggestive of mantle sources and island-arc settings. The FIC possesses low values of Yb (1.55 ppm), Nb (14 ppm) and Y (24 ppm), and high ratios of Sr/Y (27), Zr/Sm (46) and Nb/Ta (11.8), typical of magmas produced by anatexis of a basaltic slab. Partial melting models show that the FIC magma was generated by melting (F= 0.25–0.50) of a subducted oceanic crust transformed into eclogite, leaving 10–25% garnet in the residue. The FIC and similar complexes produced via slab melting during the closure of the Mozambique Ocean formed large juvenile belts along the East African Orogen that sutured East and West Gondwana together into a united supercontinent.

Porphyry mineralization in the Tethyan orogen

The Tethyan metallogenic domain (TMD), as one of the three major domains in the world, extends over 10000 km from east to west, and has developed several world-class metallogenic belts, such as the Gangdese porphyry Cu belt, the Sanjiang metallogenic belt, the Iran porphyry Cu belt, the Pakistan porphyry Cu belt, the southeastern European epithermal gold deposit belt, and the Southeast Asian Sn belt. The formation and evolution of the TMD is mainly controlled by the multi-stage subduction of Tethys oceanic slabs, the opening and closing of several small ocean basins, and continent-continent collision. The Tethys oceans include the Proto-Tethys (Cambrian-Silurian), Paleo-Tethys (Carbonaceous-Triassic) and Neo-Tethys (Jurassic to Cretaceous), which in turn are formed by rifting from the Gondwana land at different times in different micro-continents. With a series of geological processes such as oceanic opening and closing, continental collision and post-collisional reworking with intraplate deformation, various types of ore deposits are developed in the TMD, including porphyry deposits, epithermal deposits, VMS deposits, chromite deposits, Sn deposits and orogenic gold deposits. The metallogenic processes of the TMD can be categorized into three stages. (1) Oceanic subduction: With the subduction of the oceanic slab and dehydration of basalt and sediments, the asthenospheric mantle was metasomatized with preliminary enrichment in metals under oxidized condition. (2) Continental subduction: Continental collision induced partial melting of the mantle wedge enriched the metals and water in mafic melts, which ascended from subarc depths to the lower crust, locally to the shallow crust for hydrothermal mineralization. (3) Post-collisional reworking: Partial melting of the mafic intrusives in the lower crust produced felsic melts under oxidized and water-rich conditions, which underwent crystal fractionation and transferred water and metals into hydrothermal fluids for mineralization. The large-scale porphyry mineralization in the TMD mainly occurs in the Miocene, which is an important scientific issue worthy of further study in the future. How is the metal enriched in the processes of gradual maturity of the crust, and how does large-scale mineralization occur in a collisional orogen where there is no subduction and dehydration of oceanic slabs anymore to supply S and Cl? These are still important questions in the study of porphyry mineralization in the Tethyan orogen. The application of hyperspectral and mineralogical studies of alteration assemblages is beneficial for prospecting and exploration in the TMD.

PRODUCTION OF THERMAL INSULATION MATERIAL BASED ON VOLCANIC ASH DEPOSITS OF PRIMAGADANYA

Modern technologies are not standing still, and scientists are trying not only to invent new building materials, but also to find non-standard use of various raw materials that were previously considered unsuitable for use. Innovative technologies are actively used for modern construction of buildings, in particular, some types of new materials are used in the construction of various facilities. This is especially true in areas where it is not possible to import or use ordinary building materials for various reasons. Often, when designing a building, developers are wondering whether it is worth making the house warm during construction, and which insulation for the walls of the house is better to choose. This article addresses the question of which insulation for walls is most suitable for construction. The most common are mineral insulation, which are represented on the market today in the form of basalt slabs, fiberglass, etc. They have such advantages as low thermal conductivity, good thermal insulation and vapor permeability. The article presents a table with comparative performance characteristics of a mineral wool stone slab and a fiberglass slab. Stone or basalt wool has several advantages. It is able to withstand significant temperatures and temperature changes, the mats are easy to transport, convenient to install. In our opinion, a serious alternative to basalt in the production of thermal insulation materials is volcanic ash. One of the main features of volcanic ash are its building qualities, such as good thermal insulation and an environmentally friendly composition. Since here we are considering the possibility of producing insulation materials based on volcanic ash, we performed a thermal calculation of the enclosing structures. Also in the tables are the costs of transportation of volcanic ash from the field to the point of the proposed production of insulating material. Volcanic ash can be widely used in countries with high volcanic activity as an inexpensive raw material for the manufacture of building materials. It does not require additional processing and has a number of useful properties.

Permian adakitic magmatism in the Khanui Group, Northern Mongolia – Late Paleozoic slab-melting of subducted oceanic plate beneath the “Siberian continent”

The Khanui Group, the Permian volcanic rock series of northern Mongolia, is a key geologic unit in the understanding of the Permian subduction-related magmatism at the southern margin of the “Siberian continent” (Siberian craton and accreted geologic units). Several studies have been carried out in the Khanui Group, but fundamental questions on its detailed petrogenesis remain to be answered. In this paper, the lithology, stratigraphy, zircon U-Pb age, and geochemistry of the Khanui Group in the Bulgan area of Mongolia, are described, and the Permian magmatism of the southern margin of the Siberian continent is discussed. The Khanui Group in this area is composed of intermediate lava and pyroclastic rocks. The zircons from this lava give a U-Pb age of 256.9 ± 2.2 Ma, and are thus Late Permian. The lava is 53–61 wt.% SiO2, 17 wt.% Al2O3, low K2O/Na2O (avg. 0.4), high Sr/Y (avg. 97), high La/Yb (avg. 21), and comparatively high Mg# (avg. 43) which suggests that it is composed of adakites originating from subducted basaltic slab-melt. The lava is enriched in Cr and Ni compared with typical slab-melt, which likely to be the result of an interaction between the slab-melt and the overlying mantle peridotite. The Khanui rock thus confirms the existence of a basaltic slab beneath the Permian Siberian continent, and also the Late Paleozoic subduction of the Mongol-Okhotsk oceanic plate beneath the Siberian continent.

Geochemistry, age and origin of the Mons Claudianus TTG batholith (Egypt): insight into the role of Pan-African magmatism in uniting plates of Gondwana

AbstractThe tonalite–trondhjemite–granodiorite (TTG) Mons Claudianus Batholith (MCB) of Egypt is subsolvus, metaluminous to mildly peraluminous, exhibits wide ranges of SiO2, Al2O3, Sr, Rb, Zr, shows large Ba enrichment, is moderately enriched in rare earth elements (REE) and is depleted in K, Ti, Nb, Y, Hf and heavy REE (HREE), reflecting strong arc geochemical signatures. Moderate fractionation of REE and lack of Eu anomaly characterize the MCB. It is typical of high-Al TTGs of volcanic-arc affinities. U–Pb–zircon dating produced a Pan-African age of 664.12 ± 0.38 Ma. The MCB exhibits 87Sr/86Sr isotopic compositions of 0.70352–0.70626 (initial Sr ratio of 0.70259) and 143Nd/144Nd ratios of 0.51261–0.51276 (εNd; –0.5 to +2.4), suggestive of a mantle source. Anatexis of a basaltic slab under eclogitic conditions leaving garnet in the residue produces high-Al TTG rocks characterized by low Yb values (&amp;lt;1.8 ppm). Values (in ppm) of Yb (0.65–1.8), Y (2.2–19), Nb (1.2–6.4), and ratios of Nb/Ta (7–17), (La/Yb)N of 11.7, Sr/Y and Zr/Sm (58 and 45, respectively) are all consistent with anatexis of a basaltic slab under eclogitic conditions, leaving garnet in the residue to produce this high-Al TTG suite. The data conform to magma generation via partial melting (F = 0.25–0.50) leaving 15–25 % garnet in the residue. Voluminous synorogenic magmatic pulses, resulting from slab melting during the closure of the Mozambique Ocean via convergence of east and west Gondwana, produced the MCB and similar large batholiths forming the core of Pan-African belts. These belts welded together vestiges of fragmented Rodinia, assembling them into a united Gondwana.

Two (?) Lion Reliefs from Iron Age Moab: Further Evidence for an Architectural and IntellectualKoinéin the Levant?

The collection of the Karak Archaeological Museum contains two carved basalt slabs, both of which show the rear parts and hindquarters of a leonine figure. Although the two slabs differ vastly in their state of preservation, a comparison of their physical properties and iconographic features suggests that the two reliefs originally formed a matching pair and were part of a single architectural feature. Comparing the slabs to the well-known corpus of northern Levantine monumental sculpture, it is argued that the reliefs constitute the remains of two gateway figures, most plausibly dated to the Iron Age. The Karak slabs thus provide the first likely evidence for the use of architectural stone sculpture by Moabite elites, a practice most commonly associated with the Iron Age kingdoms of the northern Levant. Lion sculptures were often employed as gateways figures in public buildings, especially in the northern Levant and northern Mesopotamia, attesting to the close relationship between these images and the royal ideology they helped to project. Through their existence, the Karak slabs not only provide further evidence for cross-cultural artistic interaction in the Iron Age Levant but also suggest that ancient Karak played an important role in these exchanges.

Thermal and strength performance of reinforced self-compacting concrete slabs mixed with basalt and PVA fibers in high intensity fire

Fibers addition to concrete and the innovation of self-compacting concrete technology lead to the development of high-performance concrete. However, high intensity fire may adversely affect the performance of this type of concrete. A series of fire resistance test experiments to evaluate the performance of fiber reinforced self-compacting concrete (FR-SCC) slabs consisting of various mix of basalt and PVA fibers were carried out by subjecting the concrete slabs as an element of construction to high intensity Hydrocarbon fire heating condition. The fire testing condition was in accordance with the standard time-temperature fire curve for 120 minutes up to 1100°C heating temperature. The temperatures on the surface and within the concrete slabs were recorded and the performance of each type of FRSCC slabs were evaluated. The performance of Basalt FR-SCC was found to be more resistant to fire in comparison to PVA FRSCC. There residual compressive strength of core samples were tested and SEM analysis were carried out to determine the effect of high intensity fire on the basalt and PVA FR-SCC slabs.

Petrology and geochemistry of the Guyang hornblendite complex in the Yinshan block, North China Craton: Implications for the melting of subduction-modified mantle

The hornblendite complexes hosted in the Guyang granite-greenstone terrane form part of the Neoarchean basement in the Western Block of the North China Craton. In this study, we focus on the largest one from this block, previously named the Guyang komatiite, and present results from lithological, geochronological and geochemical studies. The dominant lithology in the Guyang hornblendite complex is greenschist facies hornblendite, and can be divided into clinopyroxene hornblendite (∼75%) and olivine-orthopyroxene hornblendite (∼25%). The oldest calculated Re depletion model ages (TRD) of these hornblendites is of 2454Ma, and the zircon U-Pb age of the wallrock is 2480Ma, with single-stage depleted mantle Nd model ages TDM1(Nd) varying from 2.61 to 2.88Ga. These data suggest that the Guyang hornblendite complexes formed during Neoarchean-Paleoproterozoic time. The hornblendites show low SiO2, high MgO contents and are enriched in Cr, Ni, and LREE with negative Ce anomalies and depleted in Ti, Nb and Ta. Their 187Os/188Os ratios range from 0.11145 to 0.11279, with γOs(2.5Ga) varying from −3.9 to +1.4. Geochemically, the olivine-orthopyroxene hornblendite shows little variation with typical cumulate feature. In contrast, the clinopyroxene hornblendite shows a large range of chemical variation. In the CaO vs. MgO and CaO/Al2O3 vs. MgO diagrams, the clinopyroxene hornblendite shows Opx fractionation trend. Combined with lithological information, we infer that the hornblendite magma was emplaced as a crystal mush, with orthopyroxene as cumulus phase. The Os and Nd isotope composition, negative Nb, Ta, Ce anomalies, and the relationships in Th/Yb–Nb/Yb diagram suggest that the Guyang hornblendites formed from a source mantle that was modified by subduction-related melts/fluids derived from a seawater-altered basaltic slab. Compared with typical Archean komatiites, the rocks of present study show significant differences in lithological and geochemical characteristics, and thus it cannot be named as komatiite. To explain these characteristics, we propose a geodynamic model involving ridge subduction and slab window mechanism to account for the formation of the Guyang hornblendite complex.

Slab and sediment melting during subduction initiation: granitoid dykes from the mantle section of the Oman ophiolite

New geochemical data are presented for a suite of tonalites, granodiorites, trondhjemites and granites intrusive into depleted mantle harzburgites of the Oman–UAE ophiolite. A detailed field, petrological and geochemical examination suggests that these ‘mantle granitoids’ are the product of three processes: (a) the mixing of melts derived from both mafic and metasedimentary sources, (b) interaction with the mantle harzburgite host and (c) the fractional crystallisation of plagioclase, hornblende ± accessory phases. Geochemical data are used to characterise the identity of the protolith(s) by first screening the data for those samples which have experienced fractional crystallisation during emplacement. The resultant ‘reduced’ data set has moderately fractionated REE, with small negative Eu anomalies and fractionated primitive mantle-normalised trace element patterns with high concentrations of fluid mobile elements and lower concentrations of HFS elements and with positive peaks for Rb and Pb and negative troughs for Ba, Nb, Sr and Ti. The character of the protolith was quantified using a melting model based upon a MORB-type basalt similar in composition to the Oman Geotimes lavas and a model using the MUQ (MUd from Queensland) global sediment composition (Kamber et al. Geochim Cosmochim Acta 69:1041–1058, 2005) both with an amphibolite/granulite facies mineralogy. The two compositions bracket the mantle granitoid data set with partial melts of the MORB source yielding trace element compositions lower than the granitoids, whereas melts of the MUQ source yield melts with compositions higher than the granitoids. Mixing of the calculated melt compositions indicates that the measured granitoid compositions represent between 10 and 30 % mixing of a metasedimentary melt into the melt of a mafic source. Current petrological, structural and geochronological data suggest a model for the origin of the Oman ophiolite in which it is formed by spreading above a subduction zone. The results of this study support this model in three ways: (a) trace element data show that the granitoids have interacted with the mantle, implying that they originated below the mantle section of the ophiolite and were emplaced into the mantle wedge from below; (b) a most probable setting for the melting of a sediment–basalt mix is in the upper part of a subducting slab; (c) the high temperature/shallow melting of the sediment and basaltic slab mix can only have been driven by the high temperatures of the overlying mantle wedge; this is most likely during subduction initiation. Thus, sediment melting during subduction initiation represents an important means of refertilising what is otherwise highly depleted mantle.

Pliocene–Quaternary basalts from the Harrat Tufail, western Saudi Arabia: Recycling of ancient oceanic slabs and generation of alkaline intra-plate magma

Harrat Tufail represents a Caenozoic basalt suite at the western margin of the Arabian plate. This rift-related suite includes voluminous Quaternary non-vesicular basalt (with fragments of earlier Pliocene vesicular flow) that forms a cap sheet over Miocene rhyolite and minor vesicular basalt. The contact between rhyolite and the basaltic cap is erosional with remarkable denudations indicating long time gap between the felsic and mafic eruptions. The geochemical data prove alkaline, sodic and low-Ti nature of the olivine basalt cap sheet. The combined whole-rock and mineral spot analyses by the electron microprobe (EMPA) suggest magma generation from low degree of partial melting (∼5%) from spinel- and garnet-lherzolite mantle source. Derivation from a mantle source is supported by low Na content in clinopyroxene (ferroan diopside) whereas high Mg content in ilmenite is an evidence of fractional crystallization trajectory. Accordingly, the Pliocene basaltic cap of Harrat Tufail is a product of mantle melt that originates by recycling in the asthenosphere during subduction of ancient oceanic slab(s). The whole-rock chemistry suggests an ancient ocean island basaltic slab (OIB) whereas the EMPA of Al-rich spinel inclusions in olivine phenocrysts are in favour of a mid-ocean ridge basaltic source (MORB). Calculations of oxygen fugacity based on the composition of co-existing Fe–Ti oxide suggest fluctuation from highly to moderately oxidizing conditions with propagation of crystallization (log10 fO2 from −22.09 to −12.50). Clinopyroxene composition and pressure calculation indicates low-pressure (0.4–2 kbar). Cores of olivine phenocrysts formed at highest temperature (1086–1151 °C) whereas the rims and olivine micro-phenocrysts formed at 712–9–796 °C which is contemporaneous to formation of clinopyroxene at 611–782 °C. Fe–Ti oxides crystallized over a long range (652–992 °C) where it started to form at outer peripheries of olivine phenocrysts and as interstitial phase with clinopyroxene.

Evolution of continental crust of the Aravalli craton, NW India, during the Neoarchaean–Palaeoproterozoic: evidence from geochemistry of granitoids

Neoarchaean–Palaeoproterozoic granitoids of the Aravalli craton, represented by four plutons with different ages, viz. Gingla (2.6–2.4 Ga), Ahar River (2562 Ma), Untala (2505 Ma), and Berach (2440 Ma) granitoids, are classified into three suites: TTG-like, Sanukitoid, and High-K Granitoid suite, all exhibiting negative Nb and Ti anomalies. The TTG-like suite is characterized by high contents of SiO2, Na2O, and LREEs, high (La/Yb)N, low contents of K2O, MgO, Cr, and Ni, and low (Dy/Yb)N, suggesting that this suite formed by partial melting of a subducted basaltic slab without interacting with a mantle wedge. In contrast, the calc-alkaline Sanukitoid suite is marked by a high content of LILEs and mantle-compatible elements, which indicate that this suite formed by partial melting of a slab-fluid metasomatized mantle wedge in a subduction-related arc environment. On the other hand, the High-K Granitoid suite is characterized by high contents of SiO2 and K2O, and low contents of Na2O, MgO, Cr, and Ni with variable Eu anomaly, along with high (La/Sm)N and (La/Yb)N, and low (Dy/Yb)N and Nb/Th. Some high-K granitoids also exhibit A-type characteristics. These features indicate that the High-K Granitoid suite formed by melting of crustal rocks. Early Neoarchaean continental crust formation reflected a slab-melting-dominated magmatic process as evidenced by the TTG-like suite, whereas Palaeoproterozoic petrogenesis was governed by the interaction of slab melt with mantle wedge as demonstrated by the Sanukitoid suite. The High-K Granitoid suite formed during the waning stages of subduction. This study reveals that granitic rocks of the Aravalli craton evolved from slab melting in the Neoarchaean to melting of mantle wedge in the Palaeoproterozoic. Melting of older crust led to the formation of the High-K Granitoid suite.

Phanerozoic sanukitoids from Caledonian Scotland: Implications for Archean subduction

Sanukitoids represent a volumetrically minor but important series of Neoarchean granitoids enriched in large-ion lithophile elements (e.g., Ba, Sr, and light rare earth elements), and with relatively high compatible elements (e.g., Mg, Ni, and Cr). Petrogenetic models have favored an origin in the suprasubduction mantle wedge, so their sudden appearance ca. 2.95–2.68 Ga has made them central to the ongoing debate about the beginnings of modern plate tectonics. Caledonian high Ba-Sr granites from the Northern Highlands of Scotland are petrological and compositional equivalents. The Caledonian examples have not undergone subsequent reworking, and their petrogenetic setting can be used to inform genetic models for sanukitoids. Prolonged subduction preceded emplacement of the high Ba-Sr granites in a short interval (∼10 Ma) at the end of the Caledonian orogeny. Sediment subduction was responsible for elemental and isotopic enrichments and slab breakoff triggered melting in the subcontinental lithospheric mantle. This implies that during the Neoarchean the evolving tectonothermal regime moved the locus of melting from the basaltic slab to the sediment-infused mantle wedge, creating the first subcontinental lithospheric mantle. Sanukitoids may then have resulted from widespread, closely subsequent slab-breakoff events, producing evolved magmas by familiar fractionation mechanisms. Careful study of secular variations in high Ba-Sr magmas could constrain the evolution of the subcontinental lithosphere.

Geochemical and Nd isotope constraints on petrogenesis of granitoids from NW part of the eastern Dharwar craton: Possible implications for late Archaean crustal accretion

Geochemical and Nd isotope data on granitoids of the NW part of the late Archaean eastern Dharwar craton are presented to elucidate their petrogenesis and role in crust formation. The granitoids are divided into three suites viz. trondhjemite–granodiorite gneisses, biotite monzogranites and porphyritic biotite granodiorites. The gneisses are pre- to syn-kinematic (with respect to deformation in the adjacent Hungund–Kushtagi schist belt), which show variable SiO 2 and Al 2O 3, enriched LREE and depleted HREE with slightly negative to no Eu anomalies. They display unusual chemistry in having higher FeO(T), K 2O, Ba, Cr and Ni compared to the typical Archaean tonalite–trondhjemite–granodiorite (TTG). The biotite monzogranites are mostly syn- to late-kinematic and exhibit evolved calc-alkaline compositions with high SiO 2, K 2O, LILE and LREE, depleted to undepleted HREE and strongly negative to no Eu anomalies. The porphyritic granodiorites show syn- to late-kinematic calc-alkaline, sanukitoid-like character with a wide range of SiO 2, higher TiO 2, P 2O 5, Sr, Ba, Cr and Ni, and lower Rb. They, however, uniquely display higher K 2O, ΣREE and Th than typical sanukitoids. The trondhjemite–granodiorite gneisses are interpreted as product of melting of a subducted basaltic slab followed by slight contamination from the overlying metasomatized mantle wedge. Subsequent melting of the extremely metasomatized mantle wedge resulted in formation of the parental magma of the porphyritic granodiorites. Intrusion of the latter triggered melting of the TTG crust accreted earlier and generated the evolved monzogranites. The monzogranites occurring east of the Hungund–Kushtagi schist belt show higher εNd but lower T DM ages than those occurring to the west, indicating that terranes with different histories were juxtaposed by lateral accretion.

The lunar rock and mineral characterization consortium: Deconstruction and integrated mineralogical, petrologic, and spectroscopic analyses of mare basalts

Abstract–The lunar rock and mineral characterization consortium (LRMCC) has conducted coordinated mineralogy/petrography/spectroscopy analyses of a suite of pristine lunar basalts. Four basalt slabs (two low‐Ti, two high‐Ti) and paired thin sections were analyzed. Thin sections were analyzed for mineralogy/petrography, while the slabs were used to prepare particulate separates of major mineral phases and bulk samples. Mineral separates and particulate bulk samples were crushed to controlled grain sizes and their reflectance spectra measured in the NASA RELAB at Brown University. The resulting data set provides an essential foundation for spectral mixing models, offers valuable endmember constraints for space weathering analyses, and represents critical new ground truth results for lunar science and exploration efforts.

Geological characteristics, metallogenic background, and genesis of the Tongyu VHMS copper deposit in the west part of the North Qinling, Shaanxi Province

The Tongyu volcanic-hosted massive sulfide (VHMS) copper deposit is located in the west part of the North Qinling (NQL), Shaanxi Province. Here we report geological features and trace elemental characteristics of ores, mineralized rocks, and volcanic host rocks of this deposit. We also conducted in situ zircon U-Pb and Lu-Hf LA-ICP-MS dating and lithogeochemical study of the Meigou granodiorite, which is intruded in the south of the Tongyu mining district. It is inferred that the volcanic host rocks of the Tongyu Cu deposit belong to calc-alkaline island arc volcanic rocks, and the volcanic host rocks and the ore-forming materials share common material sources. During subduction of the Paleo-Qinling oceanic slab at around 472 Ma, high oxygen-fugacity aqueous fluid released by dehydration reaction of the subducting slab rose into the mantle wedge, leached Cu and other metal elements, and triggered partial melting of the mantle wedge. Associated with the ore-forming materials, the arc calc-alkaline magmas erupted and formed the Tongyu VHMS deposit. The weighted average zircon U-Pb age of the Meigou granodiorite is 439.3±3 Ma, suggesting its genesis is associated with the subduction event of the Paleo-Qinling oceanic plate around 440 Ma. In terms of the granitoid’s geochemical characteristics, the Mg#, Ni, and Cr contents are high. REE show strongly fractionated patterns with unobvious Eu anomalies. Sr contents are high while Y contents are low, resulting in high Sr/Y ratios. Two-stage zircon Hf model ages mostly range between 908 and 723 Ma, with eHf(t)>0. Therefore, we classify Meigou granodiorite as island arc granite with adakitic geochemical features. It was generated by interaction between mantle wedge and melt produced by partial melting of the subducted basaltic slab of the Paleo-Qinling Ocean. The Tongyu VHMS deposit was formed in the island arc tectonic setting during Ordovician-Silurian between 439.3±3 Ma and 472±11 Ma. The volcanic exhalation-sedimentation, which was contemporaneous with the submarine volcanics, produced the primary mineralization of the Tongyu Cu deposit. Afterward, the ore bodies and host rocks were reworked and overprinted intensively by structures corresponding with the overall collisional orogenic process of the Qinling Orogenic Belt during the Indosinian period. In contrast to classic VHMS deposits such as the Kuroko deposit in Japan, the Tongyu Cu deposit possesses the dual characteristics of island arc volcanic exhalation and sedimentation as well as structural reworking and overprinting. Therefore, the Tongyu VHMS Cu deposit is a volcanic exhalation and sedimentation-structural reworking and overprinting type deposit.

The genetic association of adakites and Cu–Au ore deposits

Adakites may form by partial melting of either the subducting oceanic lithosphere or the lower part of the continental crust. These two magma types can be discriminated geochemically using a combination of La/Yb, Sr/Y ratios, MgO and Na2O contents, and Sr–Nd isotopes. Given that the basaltic crust has Cu concentrations more than two times higher than the lower continental crust and the mantle wedge, ‘primitive’ adakites produced by oceanic slab melting should contain significantly higher Cu contents than adakites derived from the continental crust, as well as normal arc andesites. A globally compiled dataset shows that Cu concentrations in adakites are generally lower than that in normal arc rocks. We attribute this low copper content to loss of magmatic fluids as a result of sulphate reduction during adakitic magma differentiation, in turn induced by the crystallization of Fe–Ti oxides, essential to mineralization. Therefore, the underflow of oceanic-slab-derived adakites that can release larger amounts of Cu (presumably Au as well) by crystal fractionation leads to higher potential for Cu–Au mineralization along convergent margins, usually associated with ridge subduction. Such basaltic slab melts initially have considerably higher Cu contents and thus play a crucial role particularly in the relatively closed magma system responsible for generating porphyry Cu deposits.