Geochemical Studies Research Articles

Plate tectonics through Earth’s history: constraints from the thermal evolution of Earth’s upper mantle

ABSTRACT Temporal changes in Earth’s tectonic style play a crucial role in understanding the planet’s evolution. Modern-style tectonics is characterized by the formation of basaltic crust at divergent plate boundaries and its subsequent recycling at subduction zones, accompanied by wedge mantle formation and arc magmatism. It is commonly believed that the secular cooling of the mantle modified the tectonic style from stagnant lid or heat pipe on an early hotter Earth to horizontal tectonics during Meso-Neoarchean. However, various field, petrographic, and geochemical studies suggest that the onset of plate tectonics ranges from Hadean to Neoproterozoic. In this study, we re-evaluate the primary magma temperature (mantle potential temperature, Tp) of the upper ambient mantle, spanning from Eoarchean to Neoproterozoic. We used basalts from several Archean and Proterozoic greenstone belts worldwide, along with Proterozoic ophiolites, to (re)calculate the Tp using the FRACTIONATE-PT method. We observed a Tp range of 1444–1639°C during the Archean and 1414–1611°C during the Proterozoic. These findings indicate a strong correlation with previously estimated Tp values obtained from PRIMELT3 method. This further highlights strong internal consistency among different methods and supports models of a hot ambient mantle during the Archean and Proterozoic. We further reviewed numerical models regarding the effect of mantle temperature on the viability of early Earth plate tectonics. Such model results, composition of Archean continental crust, recent crustal growth models, and field evidence are consistent with the operation of plate tectonics on an early hotter Earth. The transition from a hotter mantle to a colder one from Eo-Neoarchean resulted in thinner oceanic lithosphere and a less depleted lithospheric mantle. Subduction of this thinner oceanic lithosphere led to modern-style tectonics. The intensity and style of plate tectonics on the early Earth differed from modern tectonics, which emerged during the Neoarchean.

Prolonged arc accretion during growth of juvenile crust in the Arabian Nubian Shield: Insights from the granitoids of northern Ethiopia

The Arabian Nubian Shield (ANS) is one of the largest juvenile continental crust formed after the Archean. To determine the timing and understand the mechanism of its early crustal growth, we conducted geochronological and geochemical studies on granitoids from northern Ethiopia. A plagiogranite, dated at 929.7 ± 2.2 Ma, represents one of the early granitoids from the ANS. It shows low K2O, TiO2, and REE contents, flat REE pattern and absence of Eu anomaly. Moreover, it exhibits (87Sr/86Sr)i, ƐNd(t) and ƐHf(t) values of 0.70341, +5.0 and +8.4, respectively. Its zircon δ18O value is 4.8‰, lower than the mantle value. These characteristics suggest that it was derived from partial melting of altered oceanic crust. The oxygen fugacity obtained from zircon trace elements is ΔFMQ+1.3, consistent with a subduction setting.Other plutons have much younger ages ranging from 860 to 840 Ma and are mainly medium K, I-type granitoids. These granitoids show low MgO, Ni and Cr contents, low Sr/Y, (La/Yb)N, Nb/Ta and Zr/Sm ratios. They exhibit whole-rock (87Sr/86Sr)i values of 0.70236–0.70304, ƐNd(t) values of 4.2–5.2, ƐHf(t) values of 5.8–7.6 and zircon ƐHf(t) values of 5.5–10.4, slightly lower than coeval depleted mantle. Furthermore, they exhibit fractionated REE patterns, enrichments in LILE and depletion in HFSE. These geochemical features suggest that these granitoids were generated by remelting of arc crust. Compiled data show that the associated basaltic rocks are of arc affinity, which confirms the coeval development of arc magmatism in the southern ANS. Our results suggest that the growth of juvenile crust in the southern ANS started from the early Neoproterozoic and peaked at ca. 880 to 800 Ma, much earlier than those in the northern ANS. The prolonged history accounts for the growth of the vast juvenile crust in the ANS.

The Yadovitaya fumarole, Tolbachik volcano: A comprehensive mineralogical and geochemical study and driving factors for mineral diversity

Active volcanic fumaroles are one of the most spectacular natural objects in terms of mineral diversity. The Great Tolbachik Fissure Eruption (GTFE) (Kamchatka) fumaroles are renowned for its exceptional number of mineral species. The total number of minerals that have been reliably identified from this particular locality exceeds 400, which is approximately 6.5 % of all known minerals to date. In this study, we employ a comprehensive approach (bulk chemistry, microprobe analysis, powder X-ray diffraction, HR X-ray computed tomography, and 34S, 18O, and 65Cu isotope measurements) to study the distribution of primary exhalation and secondary mineral assemblages and to reveal the driving factors responsible for the unique mineral diversity in the Yadovitaya fumarole. High oxygen fugacity, the interaction of minerals with atmospheric oxygen and water from seasonal precipitation (leading to abundant hydrated mineral associations), temperature conditions controlling the spatial distribution of mineral-forming components, gas-rock interactions, and basaltic scoria morphology perfect for the crystallization of various minerals are some of the factors revealed. The combination of these factors caused a stepwise mineralization resulting in 12 zones of the Yadovitaya fumarole with characteristic mineral assemblages. The described mineralogy of the Yadovitaya fumarole demonstrates a consistent spatial evolution of fumarolic mineral assemblages that vary in complexity, chemistry, and interaction patterns with the surrounding environment. The examination of mineralogical and geochemical data yields novel insights into the active volcanic systems that are associated with the formation of distinct oxidation-type fumaroles.

Improving the re-use potential of reactive waste rock using sieving: a laboratory geochemical study

Stockpiles containing sulfide minerals are subject to oxidation reactions when exposed to atmospheric conditions, which can result in the formation of acid mine drainage (AMD). Reactive waste rock has limited re-use potential due to the contamination risk associated with the generated drainage water. The re-use of reactive waste rock could lead to a significant reduction in the volume of waste rock as it mitigates the environmental impact of mine waste deposition. Acid mine drainage generation rate depends on sulfide weathering kinetics which are controlled by many parameters such as the mineralogy and the particle size. Fine fractions of waste rock have higher specific surface areas and degree of liberation of sulfides, resulting in greater reactivity than the coarse fractions. The objective of this research was therefore to evaluate the potential of re-use by controlling particle size using the sieving method. Two different potentially acid-generating waste rocks were divided into six fractions and subjected to both static and kinetic tests. Prediction of the geochemical behavior using static test did not consider the liberation of the minerals, and the long-term prediction was therefore overestimated. Results of the kinetic columns showed there was less oxidation of the sulfide minerals in the coarse fractions than in the fine fractions. Additionally, the distribution of sulfidic minerals and neutralizing minerals with particle size is influencing the potential of the re-use of the reactive waste rock.

Integrated seismic, petrophysical, and geochemical studies for evaluating the petroleum system of the Upper Bahariya-Abu Roash G sequence in the Karama Field, Abu Gharadig Basin, North Western Desert, Egypt

The main aim of this study is to delineate the hydrocarbon potential and evaluate the petroleum system elements of the Cenomanian Abu Roash G (AR/G) and the Upper Bahariya Members in the Karama Field. It lies at the southeast borders of the Abu Gharadig Basin, a well-known basin in the W.D. to the NE of Africa. We accomplish this study by analyzing a total of thirty 2D seismic profiles, a complete data set of well logs for five wells, and their geochemical data. The workflow starts with illustrating the dominant subsurface structural features, defining the main potential reservoirs and their parameters, and checking the maturity of the probable source rocks. The seismic interpretation indicated that the research area had been influenced by a NE-SW anticlinal structure accompanied by a set of WNW-ESE and NW-SE normal faults that are controlled by the positive compression inversion process that dominated during the Late Cretaceous. Analyzing and processing the well log data sets suggest that the reservoirs of the Abu Roash G (AR/G) and the Upper Bahariya Members are characterized by poor to good reservoir settings with net-pay thickness reaching up to 13–50 feet in the different wells (av. Effective porosity (∅eff) = 17.7 % and 15.6% for the AR/G and the Upper Bahariya Members, av. Shale volume (Vsh) = 17.4 % and 13.6 %, av. Water saturation (Sw) = 38.9 % and 39.8 %, while av. Hydrocarbon saturation values (So) = 60.2 % and 61.1%, respectively). The geochemical and maturity analyses assisted in determining the potential mature source rocks of the Jurassic Khatatba Shale (TOC = 0.70–5.67%; S1+S2 = 0.43–5.97 mg/g, Ro = 0.54–1.06 %) with some contribution from the Cretaceous sources (Alam El-Bueib and Bahariya Formations). Studying elements of the petroleum regime of the Karama Field indicates that the trapped hydrocarbons are structurally controlled by three-way dip closures, horst blocks, sealing faults, and vertical sealing by impervious shale and limestone beds. This case study could be applied to similar analogs in other oil fields in the Egyptian Western Desert to delineate their hydrocarbon potential and structural setting.

Composite Melt–Rock Interactions in the Lowermost Continental Crust: Insights from a Dunite–Pyroxenite–Gabbronorite Association of the Mafic Complex from the Ivrea–Verbano Zone (Italian Alps)

Abstract The processes leading to the building of the continental crust through magmatic underplating are fundamentally unknown, mainly because of the rare accessibility to deep level sections of the continental crust. The Italian Alps expose the Permian Mafic Complex, an 8-km-thick gabbronorite–diorite batholith that intruded the lower continental crust during the post-Variscan transtensional tectonics. We present here a petrological and geochemical study of a concentric dunite–pyroxenite–gabbronorite association, called Monte Mazzucco sequence, enclosed at deep levels of the Mafic Complex, thereby allowing us to provide new insights into the magmatic processes driven by emplacement of mantle melts in deep crustal continental areas. The studied sequence includes a ~ 60-m-thick dunite lens, in which olivine (82 mol % forsterite) is associated with accessory Cr-spinel including blebs and lamellae made up of magnetite. The dunite lens is permeated by mm- to cm-scale thick magmatic veins, which range in composition from hornblende lherzolite to olivine hornblendite and hornblende websterite. The lens is mantled by a m-scale ring consisting of amphibole-bearing (≤1 vol %) websterite, and the websterite ring is in turn enclosed by amphibole-free gabbronorites. Both magmatic veins within the dunites and mantling websterites typically include an oxide association of Al-spinel and magnetite. Remarkably, the hornblende websterite veins and the mantling websterites are typically plagioclase-free and include clinopyroxene and amphibole with chondrite-normalized rare earth element patterns characterized by negative Eu anomaly. The mantling websterites display a subtle, gradual outward decrease of Mg# for orthopyroxene, clinopyroxene and accessory olivine, coupled with an increase of the negative Eu anomaly in clinopyroxene and amphibole. The enclosing gabbronorites are amphibole-free and have a chemically evolved signature. We propose a petrogenetic scenario including two major events of melt–dunite interaction. The first resulted from focused reactive melt infiltration and formed the magmatic veins within dunites. The hornblende lherzolite and the olivine hornblendite veins were produced by focused reactive melt migration through dunite grain boundaries, involving dissolution of olivine and recrystallization of Cr-spinel into Al-spinel and magnetite, whereas the hornblende websterite veins crystallized from melts penetrating through narrow fractures and recording earlier plagioclase fractionation. Most likely, the infiltrating melts were overall derived from an evolving H2O-rich magma emplaced below the dunite body. The second event of melt–dunite reactive interaction developed the websterite ring around dunites. We envision that the outermost domain of the dunite body was replaced by websterites in response to reaction with an invading H2O-poor melt, which had previously undergone plagioclase fractionation. The dunite replacement occurred under dynamic conditions, which promoted the reaction progress, thereby leading to total or almost total dissolution of precursor olivine, and started to form the lens shape of the Monte Mazzucco ultramafic association. The gabbronorites closely adjacent to the websterite ring represent the crystallization products of the invading melt.

Provenance and tectonic setting of sandstones of the Lomas Coloradas Formation, Cabullona Group, Sonora, México: Constraints on petrography and geochemistry

The sedimentary rocks of the Cabullona Group are well exposed in the Cabullona Basin of northeastern Sonora, México, which represent syntectonic sedimentation associated with Laramide-style deformation during the Campanian−early Maastrichtian. The sandstones of the Lomas Coloradas Formation deposited at the upper part of the Cabullona Group. Petrography and geochemical (major, trace, and rare earth elements) studies were carried out on the sandstones to interpret the palaeoweathering, provenance, and tectonic setting of the Lomas Coloradas Formation sandstones. Most of the sandstone modal analysis data plotted in the QFL and QmFLt ternary diagrams fall into the fields of dissected arcs and recycled orogens, respectively. Geochemically the sandstones are classified as litharenites while few samples plot into the arkosic field. The chondrite-normalized REE diagrams for sandstones have LREE-enriched, relatively flat HREE patterns with negative Eu anomalies. CIA values and the A‒CN‒K diagram indicate a low intensity of chemical weathering in the source area. The tectonic setting diagram suggests both arc and rift settings for the studied sandstones. The bivariate and ternary diagrams and elemental ratios suggest a felsic source for the Lomas Coloradas Formation. The average REE patterns of the studied sandstones are comparable with REE patterns of the granite from the Caborca block, the rhyolite and granite of the Tarahumara Formation, and the Mesozoic felsic volcanic rocks. The modeled mixture of 40% Proterozoic granite, 30% Triassic arc, 10% Jurassic arc, and 20% Laramide arc represents the probable source rocks for the Lomas Coloradas Formation.

Synchronous felsic volcanism and carbonate sedimentation as a setting for VMS deposits localization at the Salair terrane, NE Central Asian Orogenic Belt

The Salair terrane located in the northern part of the Central Asian Orogenic Belt (CAOB) contains many epithermal deposits including volcanogenic massive sulphide (VMS) deposits. The host rocks mainly consist of felsic volcanic rocks such as lavas, volcanic breccias and tuffs that associated with thick strata of carbonates. In this study, we present zircon U–Pb ages, whole rock geochemistry, and Nd isotope data from the volcanic rocks, and results of geochemical and isotope (Sr, C, O) studies of carbonates to constrain their age and petrogenesis, and to characterize the tectonic setting. Zircon U–Pb dating reveals that the ore-bearing felsic lavas have age of 519.3 ± 1.9 Ma, while the felsic tuffs have age of 516.0 ± 0.9 Ma. These volcanic rocks are characterized by high SiO2 and Na2O contents, enrichment in light rare-earth elements, remarkable negative Eu anomalies, and pronounced depletion in Nb, Ta, P, and Ti. They have depleted ɛNd(t) values ranging from +4.9 to +6.3, and young two-stage Nd model ages (from 0.82 to 0.64 Ga). The felsic volcanic rocks from the Salair terrane are interpreted as highly evolved I-type magmatic rocks that might be produced by high degree partial melting of juvenile lower crust without a significant contribution of ancient crust and without crustal reworking.Felsic volcanism was accompanied by the formation of thick strata of carbonates. These carbonates are marine limestones with Mg/Ca ratios less than 0.007, δ18O(SMOW) values from 17.1 to 23.8 ‰ and δ13C(PDB) values between –0.9 and +0.9. Their Sr isotope composition varies in a narrow range within 0.70844–0.70859 that interpreted as representing proxy for coeval seawater. These values are consistent with depositional ages of 520–510 Ma and confirms the synchronicity of the formation of carbonates and felsic volcanism. Based on the regional geology and geochemistry, the ore-host rocks of the Salair terrane were formed in the back-arc setting where the marine transgression occurred as a result of graben subsidence. It is important for better understanding epithermal deposits in the northern CAOB and might provide new insights about prospecting the VMS deposits in similar tectonic settings.

Marine Fe cycling linked to dynamic redox variability, biological activity and post-depositional mineralization in the 1.1 Ga Mesoproterozoic Taoudeni Basin, Mauritania

The concentration of redox sensitive trace metals (RSTEs) and their isotopic composition preserved in Precambrian marine sediments, are critical for the reconstruction of ocean–atmosphere oxygenation history. Particularly, the concentration of Fe, its redox speciation, and isotopic distribution, have gained widespread use for inferring the biogeochemical processes that controlled Fe cycling in Precambrian oceans linked to the reconstruction of Earth surface redox budget. However, questions remain about the biotic and abiotic processes involved in Fe cycling in these ancient oceans, including the impact of post-depositional alterative processes on the reliability of the Fe redox proxy. Here we present a multi-proxy mineralogical and geochemical study of the ∼1.1 Ga Atar and El Mreiti strata of the Taoudeni Basin in Mauritania, to better constrain pathways involved in Fe cycling, linked to Fe mineralogy, redox speciation, isotopic ratios during this time and metamorphism. We compare unmetamorphosed sedimentary deposits with facies metamorphosed by dolerite sill intrusion. The results reveal the occurrence of diagenetic Fe minerals in the basal unmetamorphosed samples associated with light δ56Fe signatures, reflecting dominant anoxic conditions that promoted microbial dissimilatory Fe reduction. Notably, δ56Fe composition of these rocks reveal several fluctuations in evolving seawater redox state from oxic to anoxic/sulfidic conditions associated with changes in sea level stand and periods of full bottom water oxygenation and redox stratification. Overall, Ce anomalies suggest a general up sequence increase in seawater oxygen content. Metamorphosed rocks display heterogeneous δ56Fe distribution, consisting of light and heavy signatures associated with secondary Fe-bearing minerals produced by metamorphic and metasomatic overprinting of carbonated rocks by hot circulating fluids. The results thus indicate metamorphic overprinting of primary seawater δ56Fe promoted by increased mobility of reactive Fe during post-depositional metamorphic transformation. They show that post-depositional metamorphic/metasomatic overprinting complicates direct reconstruction of seawater biogeochemical Fe cycling and redox state using δ56Fe systematics.

Tourmaline composition probes serpentinite-derived fluid mobility in subduction zones

Serpentinite dehydration in subduction zones plays a pivotal role in geochemical cycling on Earth. A number of geochemical studies on arc magmas have elucidated the contributions of serpentinite-derived fluids to mantle sources. However, due to complex geological overprints during subduction zone processes, discerning serpentinite signatures in exposed metamorphic rocks within fossil subduction zones remains challenging. In this study we address these difficulties through in-situ investigations of tourmaline, the geochemistry of which reflects the host environment as well as potential fluid-induced processes. The presence of zonations in tourmaline makes it an excellent recorder of consecutive geological events. Integrated major and trace elements along with in-situ boron isotopes of tourmaline from the high-pressure Sopron area (Hungary) in the Eastern Alps were used to unravel fluid action sourced from serpentinite. Despite the presence of color zoning, tourmaline in the orthogneiss (Tur-G) has low XMg [Mg/(Mg + Fe)] of ca. 0.3–0.6 and δ11B values of around −11 ‰, along with variable trace element compositions. Petrological observations and geochemical analyses suggest that the inner domains of Tur-G are of igneous origin, while the outer rims are likely affected by subsequent metamorphic events. Tourmaline in metasomatized kyanite-quartzite (Tur-K) veins exhibits distinct geochemical zoning, and preserves metamorphic cores and fluid-induced rims. The inner domains of Tur-K display low XMg (<0.6), relatively high trace element concentrations and δ11B values of less than −10 ‰, whereas the overgrowths exhibit extremely high XMg values (>0.99), low trace element concentrations and high δ11B values reaching up to +21 ‰, clearly indicating the incorporation of serpentinite-derived Mg-11B-rich fluids. Through comparison with other metamorphic and metasomatic tourmalines in (ultra)high-pressure rocks globally, we establish that tourmaline with high XMg > 0.85 and δ11B values >0 ‰ may serve as an effective proxy for detecting serpentinite-derived fluids in subduction zones.

When the Jilin-Heilongjiang Ocean was closed: constraints from zircon U-Pb and Ar-Ar dating of the Heilongjiang Complex in NE China

There has been an academic discussion and debate over the timing of the overlap and transition between the closure of the Paleo-Asian Ocean and the subduction initiation of the Paleo-Pacific Ocean. This geological process is recorded by the Jilin-Heilongjiang high-pressure metamorphic belt located at the easternmost end of Central Asia Orogenic Belt (CAOB). To address this issue, we investigated the Heilongjiang Complex exposed in Yilan and Huanan regions using geological, geochemical, LA-ICP-MS zircon U-Pb and Ar-Ar isotopic dating techniques. Geochemical studies indicate that the protoliths of the Yilan blueschist consist of subalkaline basalt formed in an oceanic island environment. The LA-ICP-MS zircon U-Pb analyses yielded zircon crystallization ages of 247±4 Ma, 259±3 Ma, 252±5 Ma and 266±3 Ma. Ar-Ar analyses yielded phengite ages of 185±2 Ma and 177± 2Ma for a micaschist and a muscovite-albite schist in Huanan area, respectively. Our findings indicate that the opening of the Jilin-Heilongjiang Ocean occurred during the late Permian to early Triassic (266-247 Ma), and its subduction occurred during the early Triassic to early Jurassic epochs (247-185 Ma). This result provides new constraints on the timing of the overlap and transition between the closure of the Paleo-Asian Ocean and the subduction initiation of the Paleo-Pacific Ocean.

Multiple mantle metasomatism recorded by Triassic post-collisional ultrapotassic and tholeiitic magmatism in West Qinling, NW China

Mantle properties and metasomatic processes, together with interlayer interactions at orogenic belts are still under debate. The post-collisional magmatic rocks could provide secondhand constraints on these issues. Hereby, an integrated geochronologic, geochemical, and isotopic study was conducted on post-collisional Zhanwa dolerites, Dashui granodiorite–monzonite-monzogabbro complex, and Jiuzigou pyroxenite–syenite complex at West Qinling. The Zhanwa dolerites, being tholeiitic with flat trace elemental pattern, were mixtures of melts from asthenospheric and oceanic slab-fluid-metasomatized lithospheric mantles. The Dashui monzonite-monzogabbro suite is ultrapotassic with strongly right-inclined trace elemental pattern and evolved isotopic composition (( 87 Sr/ 86 Sr) i = 0.7066–0.7068, ε Nd ( t ) = -4.56 to -4.35, ε Hf ( t ) = -3.14 to -2.35, and ( 206 Pb/ 204 Pb) i = 17.99–18.12)). It derived from melting of continent-crustal materials-metasomatized mantle. In contrast, the Dashui granodiorites are shoshonitic–calc-alkaline with more evolved isotopic compositions with ( 87 Sr/ 86 Sr) i , ε Nd ( t ), ε Hf ( t ), and ( 206 Pb/2 04 Pb) i of 0.7074–0.7091, -7.56 to -5.51, -5.61 to -3.53, and 18.18–18.46, respectively. They represent hybrids of mantle-derived K-rich and crustal-derived felsic melts. The Jiuzigou complex holds extremely high trace elemental contents. Its mantle source was metasomatized by both oceanic crustal fluids and sedimentary melts. Generation of these rocks (ca. 235–223 Ma) not only recorded multiple mantle metasomatism, but also captured collective asthenospheric and lithospheric magmatic responses at a post-collisional setting.

VENDIAN-CAMBRIAN SEDIMENTARY PROVENANCE OF THE UPPER KALAR DEPRESSION (ALDAN SHIELD) ACCORDING TO GEOCHEMICAL DATA

There are presented the results of geochemical studies of the Vendian-Cambrian terrigenous rocks in the Upper Kalar depression– sandstones of the Silimkun formation, exposed in the floodplain of the Kilcheris River (left tributary of the China River), in the upper reaches of the Kemen River. The rocks are enriched in Sc, Cr, Nb, V, Co, Ni, as well as in Mo and heavy rare earth elements. This study demonstrates a rare pairwise correlation between Mo and Cr. A strong positive correlation of P with Nb, Ti and Fe is indicative of P sorption phenomena in alteration products of titanium minerals (e.g. leucoxene). It has been found that the sandstones of the Silimkun Formation were formed as a result of the destruction of granitoids of the Kalar massif – presumably granite porphyries and fine-grained porphyritic biotite granites. The influence of the gabbro-norites of the Chiney complex, enriched in trace elements commonly found in rocks, is less pronounced.

Gigaton commercial-scale carbon storage and mineralization potential in stacked Columbia River basalt reservoirs

This work presents a detailed supercritical CO2 storage resource estimation for the stacked basalt reservoirs in the Grande Ronde Basalt of the Columbia River Basalt Group in eastern Washington and Oregon. The assessment aims to derisk the commercialization potential of geologic carbon storage in basalt by leveraging both structural and mineralization trapping of CO2 in basalt. The structural closures formed by anticlinal ridges and synclinal valleys in Yakima Fold Belt are excellent physical traps to accommodate injected supercritical CO2. Rigorous hydraulic testing, well logs and simulation results from the Wallula Basalt Pilot #1 well showed the occurrence of 17 suitable permeable injection zones (up to 2,496 mD) intercalated with dense seals (∼2.6E-10 mD) in the Grand Ronde Basalt. In addition, geochemical studies showed fast reactions between supercritical CO2 and dissolved basalt minerals to form stable carbonates. Our calculation indicates up to 40 gigatons (P90) of mineralization storage resources exist in the Grande Ronde Basalt reservoirs.

Geochemical Characteristics and Paleo Weathering in Sediments of Noyyal River Basin, Tamilnadu – India

A geochemical study of surface sediment samples distributed in the Noyyal River basin in western Tamil Nadu was studied for major oxides, parent rock source, and the extent of weathering. The Al2O3/TiO2 ratio of the samples ranged from (4.5-18) during monsoon and (3.94-32.14) during summer and fell in the category of mafic and intermediate igneous rocks during both seasons. The samples exhibited PIA with an average value of 64.80 during monsoon and 66.36 during summer. CIA values of the samples averaged 61.48 during monsoon and 62.35 during summer. The CIA vs. PIA, CIA vs. K/Na, and CIA vs. Al/Na for the studied samples for both seasons show low to intermediate silicate weathering in almost all locations. ICV values of samples averaged 49 during monsoon and 47 during summer suggesting that rock-forming minerals like plagioclase and alkali-feldspar are more prevalent and fewer clay minerals are present. The Al2O3/TiO2 ratio of the sample locations ranged from (4.5-18) during monsoon with an average of 10.06 and (3.94-32.14) during summer with an average of 9.94. Most of the samples fell in the category of mafic and intermediate igneous rocks during both seasons. The A-CN-K plot shows the weathering tendency towards muscovite and illite, and the A-C-N plot shows the parent rocks' plagioclases are low to intermediately weathered and the sediments gradually reduce albite and are enriched in weathering of anorthite parent material. The A-CNK-FM shows all the sediment samples lying below the feldspar region, indicating garnet and biotite presence.

3-D spatial distribution of concealed ore-forming granitoid intrusion and structures determined by the CSAMT survey of Wuxu Sb-Zn-polymetallic ore district, South China

Wuxu ore district is an important lead-zinc-antimony polymetallic ore field within the Danchi metallogenic belt of South China. Although previous geochemical studies have indicated that the deposit type is medium to low-temperature magmatic-hydrothermal, the existing metallogenic models remain controversial due to the thick covering layer and lack of exposure of granitic bodies. To address this issue, this study utilised four CSAMT parallel profiles across the Wuxu anticline to perform two-dimensional inversion, yielding high-resolution subsurface resistivity models. By comparing the resistivity anomalies along the regional strike shown by the profiles and integrating geochemical and ore deposit structural analyses, a detailed geological interpretation was conducted. A significant high-resistivity body beneath the core region of the Wuxu anticline is interpreted to be the Yanshanian period granitic intrusion. There are westward- and eastward-dipping high-conductivity belts existing within the western and eastern wings and appear to sandwich the inferred high-resistivity code of the Wuxu anticline, respectively. They may represent the deep faults extending underground and are the result of decoupling of lithological interface within the anticline and thereby rock fracturing. The high-conductivity feature may be the result of filling with high-conductivity saline fluids, and possible hydrothermal alteration. The regional compression stress during the Caledonian period and the early Yanshanian period promoted the formation of the anticline and rock fracturing of both wings of the anticline. After that, the regional extension background of the late Yanshanian period made the fault zones reactivated, becoming the site and channels for magmatic intrusion, upward transporting of hydrothermal fluid and alteration, causing lead-zinc-antimony polymetallic ore formation. The exposed ore deposits above may also corroborate this view point. In summary, our resistivity model visually depicts the spatial distribution of the granitic intrusion controlling ore formation and major structures such as anticlines, fault zones, and hydrothermal alteration zones in the 3-D space, providing new geophysical constraints for solving the controversy over the metallogenic model for Wuxu ore district.

Thermodynamic and kinetic considerations of the link between underground hydrogen storage and reductive carbonate dissolution and methane production. Are limestone reservoirs unsuitable for UHS?

Storing hydrogen underground for cyclic injection/retrieval may help move the world towards a decarbonised economy. In search of suitable long-term reservoirs, the potential reactivity of the matrix with hydrogen plays a major role. This is especially poignant for carbonate minerals, due to their abundance, ubiquity, and much faster dissolution kinetics compared to silicates. Geochemical modelling studies invariably find hydrogen-induced reductive carbonate dissolution and methane production (HIRCDAMP) whereas experimental studies, for the most part, do not support this view. To answer the question of how far injected hydrogen may oxidise, protonate and cause reductive dissolution of carbonates, a thermodynamic approach based on standard redox and overall cell potentials, as well as Gibbs free energies, was chosen. Together with observations on kinetic constraints, a consistent picture emerges in which purely inorganically driven reduction of (bi)carbonate to methane by hydrogen oxidation is not likely to occur. Rather, the formation of intermediate carbon species (e.g., formate) could be a kinetically and thermodynamically more favourable pathway than that to methane. It follows that geochemical models that question the long-term viability of hydrogen injection into carbonate-bearing reservoirs need to be revised, toning down any alleged, yet by experimental studies not substantiated, hydrogen reactivity in the absence of any catalyst and/or microbial activity.

Were South India and North China Craton attached during the Paleoproterozoic (Orosirian) Nuna Assembly? Novel geochemical and isotopic investigations of A2-type granites from the Khammam Schist Belt, Eastern Dharwar Craton, India

The paper presents novel geochemical and geochronological data from granites in Khammam, Eastern Dharwar Craton (EDC), India. The studied granites contain major mineral phases like quartz, alkali-feldspar, plagioclase, biotite, and muscovite in decreasing order of abundance. The accessory phases are epidote, titanite, and zircon. The samples comprise 70 ‐–77 wt% SiO2 and 12–15 wt% Al2O3. The K2O and Na2O concentrations range from 2.57 to 5.65 wt% and 1.17 to 2.69 wt%, respectively. They are enriched in Rb, Th, and Pb and depleted in Nb, Ta, and Ti. On a chondrite-normalized plot, the samples exhibit a rightward trend with a negative Eu anomaly. Zircon saturation in silicate melts yields a temperature (TZr) of 859 ‐ 978 °C. The microstructure and U - Pb isotopic analysis of zircon grains (n = 79) reveals the presence of magmatic and polymetamorphic grains with 207Pb/206Pb age clusters at 1844 Ma (number of analyses, n = 7) - 1858 Ma (n = 8), 1737 Ma (n = 5) -1768 Ma (n = 4), 1619 Ma (n = 7) - 1634 Ma (n = 6), and 1554 Ma (n = 5), respectively. The magmatic zircons exhibit ε(Hf) values between 3 and 18.9 with a two-stage model age of 2.03 Ga. In contrast, the metamorphic zircons exhibit ε(Hf) values between −5.6 and 18, yielding a two-stage model age of 1.97 Ga. The geochemical and geochronological studies indicate that the rocks are A2-type granite emplaced during the accretion of the eastern block of the North China Craton (NCC) and EDC between 1844 Ma and 1858 Ma. The zircons from 1737–1768 Ma and 1620 Ma show the time of metamorphic growth during Antarctica-Nellore Schist Belt (EDC) accretion. Finally, the U-Pb zircon ages from 1554 Ma represent Nuna's final amalgamation. The results of this study posit an association between EDC and NCC during Nuna assembly.

Integrating geochemical insights and remote sensing for enhanced identification of hydrothermal alterations in the Igoudrane region, Anti-Atlas, Morocco

The Moroccan Anti-Atlas is distinguished for its significant mining potential. The Igoudrane region, which is the focus of this study, is located within the Imiter inlier, one of the notable inliers of the eastern Anti-Atlas. The current study aims to evaluate the mineralogical and geochemical composition of the rocks in the Igoudrane area using the ICP-MS with 4 acids, besides identifying the hydrothermal alteration indexes using major elements provided by the geochemical data, and remote sensing techniques. The study was accomplished using the thin sections for mineralogical description, as well as the ICP-MS with 4 acids, which provides data on major, trace, and rare earth elements. The alteration indexes employed were the Ishikawa alteration index (AI), the Chlorite Saturation Index (CSI), the Sericite Saturation Index (SSI) and the Alteration Intensity coefficient (AIC). These indexes were complemented by a chloritization and sericitization mapping using the SWIR-VNIR data of ASTER. We employed the band ratios of chlorite [(B6 + B9)/(B7 + B8)] and sericite [(B5 + B7)/B6], achieving an accuracy of 80.95% for sericite and approximately 85.71% for chlorite. The mineralogical and geochemical study revealed the presence of granodiorites, granites, monzonites, monzo-diorites, diorites, gabbro, and gabbro-diorites, andesites, rhyolites, and trachydacites. These rocks belong to a highly potassic calc-alkaline and peraluminous series, which are fairly typical of granitoids of mixed origin. The plutonic rocks of Igoudrane were formed across diverse geodynamic contexts, ranging from pre-plate to post-collisional settings, and the volcanic rocks were emplaced in geodynamic settings, which are island arcs or active continental margins. The quasi-positive correlation observed in the Al vs. CSI and SSI diagrams reveals that higher aluminum content is linked to increased chloritization and sericitization intensities. Furthermore, The AIC values of the Igoudrane rocks were ranging between 52.25% and 67.53%, indicating that they have undergone moderate to high chemical alteration. The remote sensing techniques employed improve the distribution of these alteration minerals.

The Minerals That Make Up the Eastern Part of the Balkhab Copper Mine and Its Nearby Rocks

Balkhab copper mine is located in the Balkhab district of Saripul province in the Mir Sayed Murad region at coordinates E 66°46’ and N 35°35’. It is approximately 150 kilometers away from the center of Saripul province and is one of the largest copper mines in the world. The studied area is depicted on the geological map of Balkhab, along with the locations of the collected samples. The purpose of this research is to determine the characteristics of the minerals comprising of the western part of the Balkhab copper mine and its neighboring stones. To write this article, In addition to field and laboratory analyses, a number of other resources mentioned in the references have been used to complete this article. The samples taken from the copper ores were subjected to mineralogical-petrographic and geochemical analysis. This research reveals that the fundamental minerals constituting the copper ore in this area include feldspar, quartz, copper, amphibole, plagioclase, pyroxene, and iron oxide. Additionally, trace amounts of other minerals, such as pyrite, biotite, and OPECs, are present. From the geochemical study, it is seen that in addition to copper, other elements such as Silicon (Si), Sulfur (S), Iron (Fe) and Aluminum (Al) are also included in the composition of copper ore, but their amounts vary. These minerals are predominantly associated with andesitic rocks, including rhyolite, basalt, and dickite. Furthermore, sedimentary rocks like sandstone, pyrite clay, and silicic clay also contain copper minerals. The results obtained from mineralogical-petrographic analysis consistently support the same findings across various studies.