Magmatic Research Articles

Monitoring nutrient and beneficial elements in the topsoil: the function of weathered background and later surficial process on their distribution.

Monitoring the distribution of nutrient and beneficial elements (NBEs) in topsoils is important for assessing agricultural and ecological risks and for promoting human health. In order to understand their distribution effectively, it is critical to clarify their sources and main influence factors. In this study, a total of 272 topsoils and 46 soil parent material samples and some samples along 4 vertical profiles were collected in the Mentougou area of Beijing. Then, 12 NBEs were determined for each sample, including elements of N, P, S, Se, Zn, Mn, V, Ge, K, F, Ca, Mg. The mean content of 12 NBEs was statistically calculated and their spatial distributions were mapped. NBEs in topsoils were mainly influenced by the background of parent materials and the subsequent surficial processes. To address the weathered background, the study area was divided into 4 units, including igneous rocks, clastic rocks, carbonate, and loess units. For each unit, cluster analysis was performed to identify the relationship between 12 NBEs in topsoils. Furthermore, the changes in characteristics of 12 NBEs along vertical soil profiles of 4 units were individually analyzed by comparison with the weathered background. Therefore, the main factors influencing the distribution of 12 NBEs in topsoils were identified respectively. According to each element's main influencing factors, 12 NBEs were divided into 5 groups. The main influencing factors were same for elements in each group but different each other for 5 groups. Besides the weathered background, the distribution of NBEs in topsoils was significantly influenced by subsequent surficial processes, such as organic enrichment, leaching, and calcification. In addition to these natural surficial processes, the influence of human activities, a special surficial process, was also observed on the distribution of N, P, S, and Zn in topsoils in farming areas by interpreting normalized difference vegetation index (NDVI). This study provides a semi-quantitative method to determine the role of weathered background and subsequent surficial processes in the distribution of NBEs in topsoils, which helps to understand the current situation and evolution trend.

Silicate liquid immiscibility in the Chang’e 5 lunar mare magmas: constraints on the petrogenesis of lunar granitic rocks

Abstract Silicate liquid immiscibility was a common mechanism during the late-stage evolution of lunar basaltic magmas, which produced co-existing and immiscible Si- and Fe-rich melts. However, the relationship between silicate liquid immiscibility and lunar granitic rocks is debated. In this study, we investigated Si-rich melt inclusions hosted in fayalite fragments from lunar soil returned by the Chang’e 5 mission. These melt inclusions have high SiO2 (76.4 wt.%), Al2O3 (11.1 wt.%), and K2O (5.8 wt.%), and low FeO (2.8 wt.%), TiO2 (0.42 wt.%), and MgO (0.02 wt.%) contents. The texture and chemical composition indicate that these Si-rich melt inclusions formed through late-stage silicate liquid immiscibility of the Chang’e 5 mare basaltic magma. Mass balance considerations show that the unfractionated rare earth element patterns and Eu anomalies of these melt inclusions are similar to those of lunar granitic rocks. Dynamic calculations indicate that the accumulation of Si-rich melt was hindered by the high cooling rate of the Chang’e 5 basaltic magma after eruption. However, in deep-crustal magma chambers, basaltic magma would have cooled slowly and the Si-rich melt generated by late-stage silicate liquid immiscibility would possibly have had enough time to migrate upwards and accumulate to form a granitic melt body of significant size. The results of this study support the possibility that lunar granitic rocks are products of silicate liquid immiscibility.

Ultra-high temperatures recorded in parental magmas from hybrid zones

Hybrid zones commonly occur at the contact between different magmatic facies of the same batholith and/or in contact with the host rock. Fine-grained textures recorded in hybrid zones respond to quenching processes. The compositions of these fine-grained rocks are intermediate and are very close to the silica gap, typically found in calc-alkaline systems. Here, we use examples from the Axial Pyrenean Zone to distinguish types of hybrid zones and examine the potential interest in studying them. This study presents new whole-rock geochemistry, mineral chemistry, Rb-Sr and Sm-Nd isotopic data (whole-rock), and geochronological data from magmatic rocks of two plutonic complexes of the Axial Pyrenean Zone (NE Spain). Pennsylvanian calc-alkaline coarse- to fine-grained mafic-intermediate plutonic rocks, including sanukitoid series, intruded the Axial Pyrenean Zone host rocks at ca. 305.8 ± 1.6 Ma (Lys-Caillaouas gabbro), 304 ± 1.7 Ma, and 301.6 ± 1.2 Ma (La Maladeta diorite and granodiorite, respectively). Also, we reviewed the geochemical data of calc-alkaline magmatic rocks from the Pyrenees to compare them with magmas from the sanukitoid and Andean series, which allowed us to consider that they represent a mix between the two series. Petrographic and geochemical results also support that parental magmas were quenched at these hybrid zones. Near-liquidus experiments testing the parental magma composition recorded in hybrid zones shed light on the ultra-high temperatures exceeding 1000 °C for these magmas to arrive at crustal levels at near-liquidus conditions and account for the need for mantle input to generate these calc-alkaline magmas.

Origin and evolution of the Holocene magmatic system at Sakurajima volcano, Japan

Abstract Sakurajima volcano has developed since 26 ka through post-caldera magmatic activity at the Aira caldera (formed at 30 ka) and is one of the most active volcanoes in Japan. In this study, new petrological and geochemical analyses were conducted on proximal volcanic products to understand the origin and evolution of the magmatic system during the Holocene. The volcanic products have andesitic and dacitic compositions (58–69 wt.% SiO2), and relatively older products (9–1.6 ka) and younger products (<1.3 ka) are characterised by having lower and higher P2O5 contents, respectively (low- and high-P2O5 groups, respectively). The low-P2O5 group products had lower TiO2 and Y contents, higher 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios, and lower 143Nd/144Nd ratios than the high-P2O5 group products. It is suggested that the low-P2O5 group magmas were produced by the partial melting of lower crustal materials, and the compositional variations primarily reflected the variation in the degree of melting, with some contribution from mixing with mafic magmas. In contrast, the high-P2O5 group magmas were produced by mixing mafic and felsic magmas in varying proportions. The mafic end-member magmas evolved from mantle-derived primitive magmas with some contribution from crustal assimilation. The felsic end-member magmas were produced by fractional crystallisation following the melting of lower crustal materials with higher melting degrees than those of the low-P2O5 group magmas. In summary, the geochemical evolution of Holocene magmatic activity at Sakurajima was essentially controlled by intermittent discharges of partial melts from the lower crustal source region with increasing melting degrees. The remnants of the voluminous Aira rhyolitic magmas from caldera-forming eruptions were not involved in the Holocene magmatic system. Lower crustal source materials that produced the Aira rhyolites were also not involved. The lower crustal melting region, which was the main source of Holocene magmatism at Sakurajima, may have already existed at ~100 ka, well before the caldera-forming eruption at 30 ka.

An optional formula for calculating crustal thickness using Sr/Y ratio and its application to the southeastern margin of the Central Asian Orogenic Belt

ABSTRACT Though tracking changes in crustal thickness during orogenic evolution with specific element ratios has been proven effective, available empirical formulas sometimes yield unreasonable results. In this study, we proposed a new formula for calculating the crustal thickness by the Sr/Y ratio. Global lower crust-derived magmatic rock (younger than 23 Ma) data from diverse geological settings were selected and filtered using key geochemical criteria, alternating and iteratively using K-means clustering algorithm and improved Thompson tau method to exclude outliers. Curve fitting between the filtered elemental ratios and crustal thickness showed that the formula derived from maximum Sr/Y is best fitted by quadratic fitting. The rmse value between the calculated crustal thickness using the new Sr/Y formula and the true values worldwide is 14.84, lower than those of previous formulas ranging from 19.15 to 32.77. It is shown that our new formula possibly performs better for revealing temporal variations of Paleozoic crustal thickness at the southeastern margin of the Central Asian Orogenic Belt. During the Early Paleozoic Era, the crustal thickness of the Bainaimiao arc increased, corresponding to the subduction of the Southern Bainaimiao Ocean. In the Devonian, the crust in the Bainaimiao arc and northern North China Craton both continued thinning, implying for a post-collisional setting after the amalgamation between these two blocks. Crustal thickness in northern North China experienced transition from thickening to thinning, revealing a subduction-related convergent setting in the Carboniferous and an extensional setting due to slab roll-back in the Early Permian. The crustal thickness rapidly increased in the Late Permian and decreased in the Triassic, consistent with syn-collisional and post-collisional settings, respectively, associated with final closure of the Paleo-Asian Ocean. These results demonstrated that crustal thickness evolution of an orogen can be depicted in detail by our new formula and can put more insights into the understanding the complex histories of accretionary orogenic belts.

Progressive build-up of a trans-crustal system beneath an adakite-like volcanic complex (Chachimbiro, Ecuador): an example of an embryonic porphyry Cu system?

Abstract Arc magmas display global trends of increasing adakite-like indices (e.g., Sr/Y, La/Yb) with increasing crustal thickness, which are interpreted as the result of an increasingly deeper evolution of the magmas in a thick crust. Several volcanic edifices in continental arcs display a transition from normal to adakite-like magmas during their geologically short lifetimes and are precious examples to understand in detail how adakite-like signatures are acquired by magmas in thick continental arcs. Understanding the temporal transition from normal to adakite-like magmas has important implications on fundamental geological processes that are associated with adakite-like magmas, like the genesis of porphyry Cu deposits. The Quaternary Ecuadorian arc hosts numerous volcanic edifices featuring this transition during the last ~1 Ma, among which the Chachimbiro Volcanic Complex (CVC). The CVC records a history of effusive and explosive eruptions during the last ~400 ka that is characterized by progressively increasing adakite-like indices (e.g., Sr/Y, La/Yb), similar to that observed in magmatic systems associated with supergiant porphyry Cu deposits. It is therefore a suitable example to investigate the magmatic processes associated with these changes and their potential implications for the formation of porphyry Cu deposits. Here, we provide an extensive dataset on major and trace element geochemical compositions of the three main phenocryst minerals (pyroxene, amphibole, plagioclase) of the CVC. We retrieve thermobarometric data of amphiboles and pyroxenes and discuss the occurrence of different compositional clusters of the three phenocryst minerals in the frame of the ~400 ka temporal evolution of the CVC. Our data show that the oldest products of CVC, andesitic lava flows of the CH1 unit, were the result of staging of mantle-derived magmas in the lower crust and subsequent establishment of an upper crustal magma reservoir where plagioclase- and pyroxene-dominated fractionation occurred. After a magmatic lull of ~180 ka, volcanic activity resumed with effusive and explosive products of the CH2 and CH3 units characterized by more felsic compositions (high-SiO2 andesite to dacite). Thermobarometric data and contrasting REE patterns of amphiboles suggest sampling by magma coming from depth of an extensive mid- to upper crustal system at this time. The CH4 unit (~6 ka) consists of pyroclastic products which have the most evolved (rhyodacitic) composition of the whole CVC. Thermobarometric data and REE patterns of amphiboles suggest that also at this stage magmas ascending from depth sampled an extensive transcrustal system from mid- to upper crustal levels. For all evolutionary stages of the CVC, bulk rocks convey a signature that corresponds to a deeper-seated magmatic differentiation compared to magmas in equilibrium with phenocrystic minerals, which crystallized in mid- to upper crustal portions of the transcrustal system and were mechanically incorporated by magmas ascending from depth. Our study documents the progressive build-up of a transcrustal system over 400 ka during the transition to adakite-like magmatism favourable to porphyry Cu deposit mineralisation, which could represent an embryonic porphyry-related magmatic system.

Paleocene Katisho ultramafic-mafic-intermediate igneous rocks in the Ladakh Batholith, northern Pakistan: Implications for the transition from intra-oceanic to Andean type arc setting

Paleocene Katisho ultramafic-mafic-intermediate igneous rocks in the Ladakh Batholith, northern Pakistan: Implications for the transition from intra-oceanic to Andean type arc setting

Diffusion of Sr and Ba in plagioclase: Composition and silica activity dependencies, and application to volcanic rocks

Strontium and barium diffusion chronometry in plagioclase is routinely applied to mafic and felsic magmatic systems. This technique can be used to determine the timescales of magma reservoir assembly and the cooling rates of plutons and volcanic rocks, which has emerged as a useful method to assess volcanic hazards. Here we report diffusion experiments that aim to constrain the diffusivities of Sr and Ba in oligoclase and labradorite at 1 atm pressure, between 900 and 1,200°C, and assessing diffusion in different crystallographic orientations. In all of the reported experiments, silica activity (aSiO2) is buffered by varying stable phase assemblages in the diffusant source powder. The experimental products were analysed by secondary ion mass spectrometry (SIMS) depth profiling and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) line scanning. There is no resolvable dependence of Sr and Ba diffusion in plagioclase upon aSiO2 or crystal orientation. However, Sr and Ba diffusivities are found to vary as functions of the plagioclase anorthite content. As such, we parameterise the diffusivity of Sr and Ba in plagioclase as a function of temperature and anorthite content as follows:log10DSr(m2s−1)=−1.65(±0.24)XAn−3.03(±1.16)−[368,142(±27,141)2.303RT],log10DBa(m2s−1)=−1.43(±0.20)XAn−4.65(±0.96)−[337,037(±22,969)2.303RT],where XAn is the plagioclase anorthite content (mole fraction), T is the temperature (K), and R is the gas constant (J mol-1 K-1). The diffusion rate of Sr in plagioclase determined in this study is ∼1.5–2 orders of magnitude slower than previously determined, whereas Ba diffusion is similar to previous studies. This is most likely due to the Ba-feldspar stability at the experimental conditions employed by previous studies, whereas Sr-feldspar was absent from the source powder assemblage. By applying the diffusivities determined in this study to plagioclase crystals from the Cerro Galán ignimbrite (Argentina) and Santorini caldera (Greece), we find timescales of ∼105 years, with a good agreement between results from Sr and Ba diffusion modelling. Therefore, our data reconcile experimental diffusion data with measured Sr and Ba profiles in plagioclase and suggest that, at least regarding the Cerro Galán ignimbrite and Santorini caldera, plagioclase records the time needed to differentiate magma reservoirs and assemble large volumes of eruptible magma.

Geochemistry and Age Constraints of post Iron Ore Supergroup Mafic-ultramafic Magmatism in Darjing Group and Bonai Granitoid Complex, North Odisha Singhbhum Craton, India

ABSTRACT Mesoarchean mafic-ultramafic magmatic activities show a regular pattern in different cratons across the world and it starts with peridotitic members to pyroxenite to Geochemical Analog of Boninite (GAB) to Siliceous High Magnesium Series (SHMS) type. Magmatic activities with similar geochemical characteristic and same evolutionary trend i.e., from ultramafic to GAB to SHMS are observed in enclaves of BGC and sill of Darjing Group. Based on coherent geochemical character and intrusive field relation of these two mafic-ultramafic suites of rocks, it can be concluded that they are cogenetic and emplaced late to post first deformation of Iron Ore Supergroup orogeny with an Archean geochemical analog of modern island arc setting. Erstwhile these were classified as two different stratigraphic units. Geochemical data also indicates an enriched mantle source for this event. Besides, geochronological constraints specify its intrusion time (~2.9 Ga to ~3.0 Ga) that can be appraised with other similar events from Singhbhum Craton as well as from other cratons of different part of the world.

Tectono-sedimentary processes shaping the West Sardinian margin and adjacent oceanic basin during the Plio-Quaternary (Western Mediterranean Sea)

A seismic analysis of the Plio-Quaternary stratigraphy of the West Sardinian continental margin and adjacent oceanic basin was conducted using single- and multi-channel seismic profiles. Two main chronostratigraphic boundaries have been used: i) the Ms. horizon, marking the base of the Pliocene and corresponding to the top of the Messinian evaporites on the lower continental slope and deep basin, and the Messinian erosional truncation on the upper slope and shelf; and ii) the newly identified A0 horizon, marking the base of the Quaternary (2.6 Ma). This study reveals key geological features affecting the Pliocene and Quaternary deposits: a) salt tectonic structures, b) normal faults, c) volcanic structures, d) pockmarks, e) canyon systems, and f) regressive clinoform system. These features are linked to tectono-sedimentary processes such as vertical movements, magmatic activity, halokinesis and sediment dynamics. Vertical movements are associated with the thermal subsidence of the Oligo-Miocene basin opening, water and sediment loading/unloading during and after the Messinian Salinity Crisis, and Pleistocene uplift onshore. These movements resulted in the tilting of the margin, which influenced normal faulting through reactivation of Oligo-Miocene faults, and the Plio-Quaternary depositional patterns. Several normal faults acted as conduits for lower Pliocene magmatic activity and gas migration, forming volcanoes and pockmarks on the continental shelf and upper slope. Salt tectonics in the lower slope and deep basin produced diapirs and rollover structures, significantly impacting the thickness and distribution of Pliocene and, to a lesser extent, Quaternary deposits. Canyons system formation seems to be controlled by the interplay of the Quaternary sea-level fluctuations with the margin's ongoing tilting. Similarly, the regressive clinoform system also results from these two factors, but is further influenced by erosion of uplifted Sardinian onshore areas.

Thermal conductivity of igneous rock cores estimated from shallow wells drilled within the Las Tres Vírgenes volcanic complex, BCS, Mexico

Thermal conductivity of igneous rock cores estimated from shallow wells drilled within the Las Tres Vírgenes volcanic complex, BCS, Mexico

Hidden Archaean basement beneath the southwestern Yangtze Craton: Evidence from 2.8 Ga xenocrystic zircons in an early Cretaceous dolerite dyke

The distribution of Archaean basement rocks in the southwestern Yangtze Craton, China, is not well documented due to the scarcity of outcrops. In this study, we identified Meso–Neoarchaean zircons in a dolerite dyke that was emplaced in the Meso–Neoproterozoic Dongchuan Group in the southwestern Yangtze Craton. Ninety-seven analyses of zircons from the dolerite yielded two distinct U–Pb age groups. The younger group of zircons, characterised by euhedral crystals and relatively high Th/U ratios (0.15–2.03), has a weighted-mean age of 109.4 ± 3.0 Ma (n = 27), which is considered to be the emplacement age of the dolerite. The older group of zircons, with a weighted-mean age of 2831 ± 18 Ma (n = 33), crystallised during the Meso–Neoarchaean. These zircons might be xenocrysts captured during magma emplacement. Moreover, the zircons have εHf(t) values of −24.59 to −4.16 for the young population and −9.80 to −3.86 for the old population, indicating the dolerite was derived by melting of Archaean crustal igneous rocks. These results demonstrate the existence of Archaean rocks in the southwestern Yangtze Craton and provide new evidence for the spatial distribution of Archaean basement.

In-depth experimental and numerical investigations of a rock-bed thermal energy storage system: Insights from mafic versus felsic igneous rocks

In-depth experimental and numerical investigations of a rock-bed thermal energy storage system: Insights from mafic versus felsic igneous rocks

Quartz textures, trace elements, fluid inclusions, and in situ oxygen isotopes from Aktogai porphyry Cu deposit, Kazakhstan

Abstract The Paleozoic Aktogai Group in Kazakhstan ranks among the 30 largest porphyry Cu deposits globally. The Aktogai deposit is the largest one in the Aktogai Group and is characterized by intensive potassic alteration where the dominant orebody occurred. However, its mineralization processes still need to be clarified. Our investigation focused on the texture, trace elements, fluid inclusions, and in situ oxygen isotopes of the quartz from the ore-related tonalite porphyry and associated potassic alteration at Aktogai to trace the deposit’s mineralization processes. Ti-in-quartz thermobarometry, fluid inclusion microthermometry, and geological characteristics indicate that the ore-related magma at Aktogai originated from a shallow magma chamber at ∼1.9 ± 0.5 kbar (∼7.2 ± 1.9 km) and intruded as the tonalite porphyry stock at ∼1.7–2.4 km. The potassic alteration and associated Cu mineralization comprise five types of veins (A1, A2, B1, B2, and C) and two types of altered rocks (biotite and K-feldspar). Among them, nine types of hydrothermal quartz were identified from early to late: (1) VQA1 in A1 veins and RQbt in biotite-altered rocks; (2) VQA2 in A2 veins and RQkfs in K-feldspar altered rocks; (3) VQB1 in B1 veins and VQB2E in B2 veins; and (4) quartz associated with Cu-Fe sulfides (VQB2L, VQBC, and VQC) in B and C veins. Titanium contents of the quartz decreased, while Al/Ti ratios increased from early to late. Fluid inclusion microthermometry and mineral thermometers reveal that VQA1, RQbt, and hydrothermal biotite formed under high-temperature (∼470–560 °C) and ductile conditions. VQA2, RQkfs, VQB1, and hydrothermal K-feldspar formed during the transition stage from ductile to brittle, with temperatures of ∼350–540 °C. The rapid decrease in pressure from lithostatic to hydrostatic pressure led to fluid boiling and minor involvement of meteoric water (∼11–14%) in the mineralizing fluid. Extensive recrystallization in VQA1 to VQB1 was associated with repeated cleavage and healing of the intrusion. With cooling, K-feldspar decomposition and hydrolysis increased. Fluid cooling and water-rock reactions resulted in the co-precipitation of Cu-Fe sulfides, white mica, chlorite, VQBC, and VQC at temperatures of ∼275–370 °C and brittle conditions. The Paleozoic Aktogai deposit exhibits formation depths and fluid evolution processes similar to Mesozoic and Cenozoic porphyry Cu deposits worldwide. The close association between Cu-Fe sulfides and later quartz formed under intermediate-temperature conditions at Aktogai implies that Cu-Fe sulfides are not precipitated under early high-temperature conditions in porphyry Cu deposits.

The timing of the Middle Triassic magmatism in the Dolomites area (Southern Alps, Italy): U[sbnd]Pb geochronology of zircon and titanite hosted in plutonic rocks and phonolite dykes

The Middle Triassic magmatic event in the Southern Alps (Italy) is characterised by the emplacement and eruption of multiple magma batches with different geochemical affinities in a short time span. In this work, we present the first geochemical and geochronological data on highly differentiated alkaline dykes (phonolites) exposed in and near the Middle Triassic Predazzo magmatic complex (Southern Alps, Italy) and a first complete geochronological survey of the Predazzo pluton. The phonolites, cutting the Middle Triassic volcanic sequences, are sodalite- and aegirine-bearing and have titanite, apatite and magnetite as accessory phases. Their trace element concentration reflects a geochemical signature similar to the orogenic-like signature typical of the Middle Triassic magmatic rocks of the Predazzo complex. New in situ UPb dating on titanite from the phonolite dykes and UPb dating on zircon separates from all the magmatic units of the Predazzo pluton show that the phonolite dykes were emplaced between 233.8 ± 3.1 Ma and 238.1 ± 4.5 Ma, i.e., overlapping to and postdating the emplacement and crystallisation of plutonic rocks, which yield ages ranging from 237.97 ± 0.15 Ma to 238.31 ± 0.13 Ma. The ages obtained for the diverse suites of the pluton are in good agreement with previous dating and show that silica-saturated to -undersaturated rocks were placed within the same context in a short time span. Thermometry and hygrometry on titanite, clinopyroxene and K-feldspar revealed that phonolites represent volatile- and REE-rich (H2O = 8 ± 0.6 wt%) highly differentiated alkaline melts intruding at relatively low T (752–868 °C), which easily caused the spatially related CuW mineralisation. Comparisons with sub-volcanic rocks exposed in the Central (Edolo) and Western Alps (Finero mafic complex) indicate that the phonolites still preserve the orogenic signature of the Middle Triassic event in the Southalpine, that characterise all magmas emplaced before the opening of the Alpine Tethys in the Late Triassic. These new geochronological constraints on the Predazzo pluton and phonolite dykes enable us to outline the complete sequence of magmatic events associated with the emplacement of the Predazzo volcano-plutonic complex during Mid-Triassic and to speculate about the genesis of CuW mineralisation.

Magma Beneath Yellowstone Is Shifting Northeast

Though the volcano’s magma chambers could hold enough material for a caldera-forming event, none of them are likely to erupt soon.

Characterizing a complex buildup in the Pearl River Mouth Basin of the northern South China Sea: an interplay of carbonates and igneous rocks

Volcanic mounds and carbonate buildups share similar geometries, making their differentiation in seismic data a significant challenge. This challenge is further compounded in complex buildups composed of both multi-stage developed igneous rocks and biogenic carbonates. To address this gap, this study investigates a mixed carbonate-igneous buildup at the central of the Baiyun Sag in the northern South China Sea. By analyzing the lithofacies of the carbonates and igneous rocks, the morphological features and spatial distribution patterns corresponding to these sedimentary and volcanic facies were identified. Well-to-seismic calibration was used to delineate the stratigraphic units, and typical seismic profiles of the buildup were analyzed. Eight distinct seismic facies were identified for carbonates and igneous rocks. The evolution of the buildup is divided into three stages: (1) volcanic eruptions and carbonates development, (2) overflowing magma and reef shoal deposits, and (3) reef-bank deposition accompanied by igneous intrusion. We propose that volcanic rocks can be distinguished from carbonates by the temporal and spatial coupling of typical features: (a) surface volcanic rocks and subsurface intrusive bodies are inseparable, with igneous rocks identifiable through faults and volcanic conduits; (b) carbonates typically display symmetrical structures on both sides of the highland and exhibit better stratification away from igneous activity; (c) carbonates generally show a convex clinoform and steep slope at the platform margin, while volcanic mounds exhibit concave gentle slopes. Furthermore, the analysis of high-quality reservoir development within the complex buildups is instrumental for advancing oil and gas exploration in volcanic seamounts and carbonate buildups.

Isotopic composition (U-Pb, O) of zircons from Variscan igneous rocks in the Kraków–Lubliniec zone and adjacent areas in SHRIMP IIe/MC ion microprobe studies

Isotopic composition (U-Pb, O) of zircons from Variscan igneous rocks in the Kraków–Lubliniec zone and adjacent areas in SHRIMP IIe/MC ion microprobe studies

Late Triassic Felsic and Mafic Magmatism in the South Qinling Orogen, Central China: Insights from the Petrology, Zircon U-Pb Geochronology, and Geochemistry of the Huoshaodian Pluton

The petrology, geochemistry, and zircon U-Pb chronology of the Huoshaodian pluton in the Liuba area of the western part of the South Qinling tectonic belt are investigated in this study. The Huoshaodian pluton consists of gabbro, quartz diorite, and granodiorite, and the dominated rock type is quartz diorite. The results indicate that the Huoshaodian pluton belongs to the calc-alkaline series. In the chondrite-normalized REE, all of the samples showed similar patterns, with an enrichment of light REEs and depletion of heavy REEs, but they showed slight differences in the degrees of Eu anomalies. The primitive mantle-normalized trace element diagram reveals an enrichment of large-ion lithophile elements (LILEs) and light rare earth elements (LREEs), as well as depleted high field strength elements (HFSEs). The zircon U-Pb dating results reveal that the gabbro, quartz diorite, and granodiorite have crystallization ages of 214.9 ± 0.58 Ma, 215.0 ± 1.2 Ma, and 215.4 ± 1.9 Ma, respectively, indicating that the Huoshaodian pluton was emplaced during the late Triassic period (214.9–215.4 Ma). In terms of petrogenesis, the gabbro of the Huoshaodian pluton originates from a transitional lithospheric mantle that has undergone fluid metasomatism and partial melting. Specifically, it originated through 1%–2% garnet spinel peridotite undergoing partial melting. In addition, the gabbro underwent a slight degree of contamination by crustal materials during its ascent and intrusion, with some continental crust material being incorporated. The quartz diorite and granodiorite of the Huoshaodian pluton are formed through partial melting processes occurring within the normal lower crust. Combined with the previous studies on the early Mesozoic tectonic evolution of the South Qinling, this study proposes that the formation mechanism of the Huoshaodian pluton may be as follows: in the early Triassic, the Mianlue Ocean subducted northward beneath the Qinling microblock, resulting in a large-scale continental-continental collision between the North China Block and the Yangtze Block; when the oceanic crust subducted to a certain depth, the detachment of the subducting slab triggered the upwelling of mantle material. The heat from mantle-derived magma caused the partial melting of the mafic lower crust, while the mafic magma entered into the upper granitic magma chamber and began to mix. Due to the high viscosity contrast and temperature difference between the two end-member magmas, incomplete mixing led to the formation of a melt with distinct adakitic characteristics and a mafic melt representing mantle-derived material.

Utilizing of Geophysical Methods for Geothermal Exploration at Guru Kinayan Village, Tanah Karo Regency

Guru Kinayan, located at the foothills of mount Sinabung in Karo regency, is characterized by several geothermal manifestations, highlighting the necessity of studying its geothermal potential. This research aims to assess the geothermal prospects of the area through 2-D electrical resistivity, geomagnetic surveys, and (XRD) methods. To acquire 2-D resistivity data, a Wenner Schlumberger array with a 5-meter electrode spacing was utilized, and the data were processed using Res2Dinv. Geomagnetic surveys were conducted using a PPM, with the results analyzed using Mag2dc and Surfer 13 to determine susceptibility results. The analysis of rock composition was performed using XRD. The 2-D resistivity results indicated resistivity values ranging from 1 to 1250 Ωm. Values between 1 and 20 Ωm indicated as alluvium, indicating a reservoir for geothermal, while resistivity values >1000 indicates as limestone, which indicated as a heat conductor. The magnetic residual map shows geomagnetic values (20 to 380 nT), suggesting a geothermal source, and the susceptibility values ranging (0.0013 x 10³ to 0.0088 x 10³) indicates the presence of igneous rocks, specifically andesite lava and pyroclastic rocks. The XRD results show arsenopirit and quartz in the geothermal area. Based on the integrated results, the study area has significant geothermal potential.