Granitic Units Research Articles

New insights on the origin for rapakivi granites: U-Pb and Lu-Hf in zircon from Alto Candeias Intrusive Suite, Amazonian Craton, Brazil

The Southwestern Amazonian Craton, in Rondônia state, Brazil, comprises multiple orogens with ages ranging from 1.8 to 1.0 Ga, where successive magmatic, metamorphic, and deformational processes reworked ancient rocks and produced new complexes and juvenile continental crust. Identification of the geochronological and petrographic characteristics of granitoids and terranes generated during such events is crucial for the recognition and distinction of their magma sources. A total of 64 samples collected from the Alto Candeias Intrusive Suite outcrops in Rondônia state recognized four different groups: (1) Monte Negro unit (rapakivi granites), (2) Buriti unit (equigranular to porphyritic granodiorites), (3) Campo Novo unit (medium to coarse-grained charnockites), and (4) Jacilândia unit (fine-grained granites). U-Pb geochronological data were obtained for each unit, with the following ages: 1350 ± 5 Ma (Monte Negro unit), 1350 ± 2 Ma (Buriti unit), 1349 ± 3 Ma (Campo Novo unit), 1348 ± 3 Ma, and 1349 ± 1 Ma (Jacilândia unit). The ages of the four granitic units are the same within error. Lu-Hf isotopic results presented in this study indicate that the Alto Candeias Intrusive Suite has the mantle as the magmatic source and that the continental crust coeval to the subduction process. This process led to the formation of I-type granitoids generated in the SW margin of the Amazonian Craton around 1350 Ma during San Ignacio orogeny.

Unravelling the magmatic and hydrothermal evolution of rare-metal granites through apatite geochemistry and geochronology: The Variscan Beauvoir granite (French Massif Central)

Peraluminous rare-metal granites (PRMGs) represent highly differentiated crustal granites characterised by extreme enrichment in metals, such as Li, Sn, Nb, Ta, W, and Be. This geochemical specificity is considered to be the result of a succession of magmatic and hydrothermal processes, the importance and individual impact of which are still debated. In this study, we investigate the magmatic and hydrothermal evolution of the Beauvoir leucogranite, a world-class PRMG from the French Paleozoic Variscan belt, through extensive characterisation of suprasolidus to subsolidus apatite. We employ a multi-tracing approach, combining in-situ elemental compositions (major, trace, and halogen elements), oxygen isotopic systematics, and U-Pb geochronology.Four major magmatic and hydrothermal stages were identified through apatite petrography and U-Pb geochronology. Magmatic apatite crystallised at 314.6 ± 4.7 (2s) Ma. Decrease in the amplitude of the Eu anomaly in magmatic apatite from the deeper to shallower granitic units record an increase in the oxygen fugacity (fO2) of the magma with differentiation, likely contributing to the crystallisation of a first and predominant cassiterite generation. Magmatic apatite REE patterns show significant tetrad effects; they reflect the exsolution of magmatic fluids involved in the precipitation of early hydrothermal apatite replacing igneous minerals or precipitating within veins during greisenisation episode dated at 314.3 ± 5.5 Ma and 311.7 ± 8.1 Ma. Early hydrothermal apatite, characterised by enrichment in Sr or S and Mn-REE depletion along with variable Br/I ratios and δ18O compositions down to negative values, record mixing dynamics between two fluid end-members: (i) magmatic fluids, and (ii) oxidising meteoric fluids partially reequilibrated with country rocks. Meteoric fluids progressively invaded the Beauvoir PRMG at temperatures ≥ 450 °C and triggered precipitation of a second generation of cassiterite during mixing with magmatic fluids. Two late, non-magmatic, hydrothermal events are dated at 268.3 ± 20.4 Ma and 148.5 ± 26.6 Ma. Related apatite is marked by specific mineralogical and geochemical features such as high As contents and heavy oxygen isotope signatures. They are proposed to be linked to extension-related regional hydrothermal fluid circulation that contributed to metal endowment (U, F-Ba-Pb-Zn) in the crystalline basement and overlying sedimentary cover of Western Europe following the Variscan Orogeny.Our results demonstrate that apatite is a key mineral to decipher the role of magmatic and hydrothermal processes leading to ore deposition and remobilisation in PRMGs, in relation with geodynamic evolution. Apatite records of external fluid incursions at near-solidus conditions highlight the open system nature of the Beauvoir PRMG, which is crucial for developing fully integrated metallogenic models applicable to similar deposits.

New insights into the petrogenesis of granitic rocks in southern Thailand, SE Asia tin belt: evidence from petrochemistry and geochronology

ABSTRACT The granitic rocks in the Prachuap Khiri Khan Province, southern Thailand, SE Asia Tin Belt, comprise gneissic biotite monzogranite, porphyritic muscovite–biotite monzogranite, and porphyritic biotite monzogranite. Comprehensive field observations, petrography, mineral chemistry, and geochemistry establish gneissic biotite monzogranites as part of the Central Belt Granites (CBGs), while porphyritic muscovite–biotite monzogranite and porphyritic biotite monzogranite as part of the Western Belt Granites (WBGs). CBG and WBG granitic units exhibit peraluminous, alkali-calcic, and magnesian magmatic series traits, reflecting an S-type granite character resulting from crustal partial melting. Significantly, scatter correlations in variation diagrams, combined with the enrichment of Cs, Rb, Th, U, Pb, Nd, and P, and the depletion of Ba, Nb, and Ti contents, point towards an S-type granite signature formed during collisional events. Crystallization conditions reveal CBG gneissic biotite monzogranite encountered P–T conditions of 2.97–3.85 kbar/680°C–733°C/11.1–14.4 km, while WBG’s porphyritic muscovite–biotite monzogranite and porphyritic biotite monzogranite experienced 2.73–4.15 kbar/628°C–732°C/10.2–15.5 km and 2.47–3.80 kbar/651°C–728°C/9.2–14.2 km, respectively. Geochronological data indicate that CBG’s gneissic biotite monzogranite was emplaced from Early Cretaceous collision (128–119 Ma) of Indochina and Sibumasu terranes, while WBG’s porphyritic muscovite–biotite monzogranite and porphyritic biotite monzogranite were formed during the syn-collision of Sibumasu and West Burma terranes during Early Cretaceous (121–111 Ma) to Paleocene. Mineralogical and geochemical attributes of these granitic rocks exhibit strong relevance to Sn-W mineralization processes, indicative of a profound association.

Tin-polymetallic mineralization and granitic rocks in the Nanling daping mining area: Geochemical and geochronological constraints

The Daping polymetallic deposit in the Nanling is a recently discovered deposit with significant potential in the Dayishan area. High-precision geochronological studies indicate that the emplacement ages of two fine-grained porphyritic (containing tourmaline) biotite granite units are 153.2 ± 0.9 Ma and 152.3 ± 1.0 Ma, representing products of the fifth magmatic activity in the Dayishan intrusion. The cassiterite U-Pb ages from the residual skarn type and greisen-type tin ores are 153.4 ± 3.6 Ma and 150.22 ± 0.37 Ma, respectively, and they are consistent within the error range, both belonging to the Yanshanian Early period. Petrogeochemical analyses of the granite reveal characteristics of high silica content (73.56 ∼ 75.91 %), alkali (K2O = 4.04 ∼ 5.58 %, Na2O = 2.22 ∼ 3.67 %), low calcium (0.42 ∼ 0.80 %), low magnesium (0.075 ∼ 0.29 %), and peraluminous nature (A/CNK = 1.26 ∼ 1.35). The rare earth element (REE) contents range from 35.78 × 10-6 to 111.57 × 10-6, with δEu values between 0.006 and 0.026, LREE/HREE ratios of 2.23 ∼ 3.41, and (La/Yb)N values of 1.20 ∼ 2.42. The granite is enriched in elements such as Rb, K, Th, U, Nd, Hf, and depleted in Ba, Sr, P, Nb, Ti, indicating strong crystal differentiation in the area. Sr, Nd, and Hf isotope studies show that the granite samples have ISr values of 0.67612–0.70040, εNd(t) values of −5.83 ∼ -8.23, εHf(t) values of −6.1 ∼ -1.9, (Nd)TDM2 values ranging from 1361 to 1573 Ma, and (Hf)TDM2 values ranging from 1147 to 1408 Ma. It is proposed that the Dayishan intrusion originated from the mixing of a mid-Paleoproterozoic mafic rock and a metamorphic sedimentary source region, with the latter being predominant. The detachment of source rocks from the mantle reservoir occurred in the mid-Paleoproterozoic. Combining lithological, petrogeochemical, and comparative analyses, it is classified as a highly fractionated A-type granite formed in a local extensional setting related to the subduction of the Pacific Plate. Additionally, this paper constructs a ore-forming model for the Daping tin deposit, aiming to provide reference for regional rare metal ore exploration.

Heat sources for Variscan high‐temperature–low‐pressure metamorphism: Petrochronological constraints from the Trois Seigneurs massif, French Pyrenees

AbstractHigh‐temperature–low‐pressure metamorphism is commonly associated with intermediate to felsic magmatism in continental orogenic belts. The heat budgets and transfer mechanisms responsible for such elevated temperatures and partial melting of the upper crust are uncertain. The Trois Seigneurs massif, French Pyrenees, preserves a structurally continuous record of Variscan high‐temperature–low‐pressure metamorphism through a sequence of upper‐to‐mid‐crustal Paleozoic metasedimentary rocks. Conventional thermobarometry and phase equilibria calculations show that metamorphic conditions span ~2.5 kbar, 575°C to suprasolidus conditions of ~6 kbar, 700°C. Peak temperatures depend strongly on depth: temperature gradients of 50–60°C/km are present through the uppermost 12 km of the section; deeper portions (12–20 km) define restricted temperature conditions of ~650–700°C. The lowest‐grade metamorphic rocks preserve the largest spread in monazite 206Pb*/238U dates, from c. 325–285 Ma, while the spread in dates is restricted to c. 305–290 Ma in the highest‐grade rocks. Within this spread, each sample yields a well‐defined population of monazite 206Pb*/238U dates with peaks at c. 305 Ma in the andalusite schists, 295 Ma in the sillimanite schists, and 300 Ma in the migmatite sample. Monazite trace‐element compositions capture a systematic change with decreasing date and increasing metamorphic grade, including a more negative Eu‐anomaly and decreasing Sr concentrations, consistent with co‐crystallizing feldspar; increasing HREE and Y contents, consistent with xenotime breakdown; and decreasing Th/U, reflecting increasing U content during breakdown of inherited zircon. Zircon rims from a granite unit that formed via partial melting of the Paleozoic sedimentary package yields a 206Pb/238U‐207Pb/235U concordia age of 304.1 ± 3.73 Ma. These rims have trace‐element compositions reflecting cogenetic apatite and zircon growth during granite formation. Zircon from a calc‐alkaline granodiorite intrusion preserves a 40 Ma record of melt‐related activity in the lower crust that preceded the regional thermal climax. We interpret these petrochronological data to show that the Trois Seigneurs field gradient including andalusite schist and biotite granite samples represents a genuine geotherm through Variscan orogenic crust during the regional thermal climax at 305 Ma. When combined with constraints from other Pyrenean massifs, the form of the geotherm is consistent with a thermal scenario in which heat is advected to the upper crust by intermediate‐composition magmas generated in the lower crust. A simple thermal model for this process indicates that anatexis in the upper crust may plausibly occur within 10 Ma of the initiation of the lower‐crustal melting. Such a thermal scenario, however, requires focusing of melt through a fertile lower crust and an elevated Moho heat flux. We suggest that this process may have controlled the attainment of high‐temperature–low‐pressure metamorphic conditions along the Variscan belt and may currently be operating in zones of post‐orogenic continental extension.

Petrogenesis and REE mineralogical characteristics of Shitouping granites in southern Jiangxi Province: Implication for HREE mineralization in South China

The enrichment of heavy rare earth elements (HREE) in the granitic host-rocks is crucial for generating ion-adsorption HREE deposits in South China. The Shitouping pluton, located in the southern part of Jiangxi Province, South China, develops large-scale HREE deposits in its weathering profile identified by recent geological surveys. These granites can be divided into medium to coarse-grained biotite monzogranite (MGBG), medium to coarse-grained syenogranite (MGSG) and fine-grained alkali feldspar granite (FGAG) based on field observations and mineral assemblages. New geochronologic results show that this composite pluton intruded during the Early Cretaceous (ca. 140 Ma). Three granitic units displaying comparable whole-rock Nd [εNd(t) = −4.5 to −3.4] and zircon Hf compositions [εHf(t) = −4.4 to +1.2], combined with mineral association, hydrothermally altered zircon and whole-rock geochemistry, indicate they were derived from partial melting of hybridized crustal source, followed by intense fractional crystallization and fluid metasomatism in the highly evolved granitic system. The MGSG and FGAG have higher Rb, Nb, HREE contents and Rb/Sr ratios, as well as lower Nb/Ta, K/Rb ratios in comparison with the MGBG, implying they are more evolved units. The overlapping magmatic zircon trace element compositions between MGBG and MGSG, coupled with the subvertical contact boundary between the FGAG and the MGBG, suggest that the generation of Shitouping pluton should be attributed to the periodic magma replenishment, remobilization, and differentiation process in the long-lived magmatic system rather than simple fractional crystallization from a single parental magma. Hydrothermally altered zircon with elevated concentration of HREE and the paragenetic relationship between LREE-phosphate and HREE minerals in the MGSG suggest that the fluid metasomatism promotes the migration and accumulation of HREE. This is consistent with the high HREE concentration recorded in the MGSG, which contains abundant HREE minerals associated with fluorites. Thus, this study highlights that magma differentiation and fluid metasomatism during the late magmatic stage could achieve the relatively high HREE contents in granites to favor the formation of ion-adsorption HREE deposits.

Spectral analysis of aeromagnetic data over parts of Southwestern Nigeria

This study endeavors to assess spectral depths, explore Basement structure variability, and deduce geothermal heat distribution by determining Curie point depth (Zb) through aeromagnetic data analysis across 14 sheets in Southwestern Nigeria. The depths to the shallow magnetic source (Zt) range from 0.14286 km to 1.02632 km, indicating sediment thickness, with the deepest point situated in the Northwestern region and progressively shallower towards the central and Southern portions of the study area. Depths to the deeper magnetic source (Z0) span from 1.08333 km in the North-central part to 3.23529 km in the Southwestern part. The primary sources of the first layer (Zt) depth are intrusions/outcropping Basement rocks, while the second layer (Z0) results from the intrusion of magnetic rocks into the basement, intra-Basement fissures, and deeper magma intrusions below the bedrock. Curie point depth ranges from 1.87380 km to 6.25629 km, with the North-central region exhibiting the shallowest depths, followed by the Northeast, Northwest, and Southeast. Shallow Curie point depth is attributed to magma upwelling and magmatic intrusion in highly fractured quartzite units and older granite units, while deeper Curie point in the Southwestern part may result from isostatic compensation/recovery. Given that Curie point depths are shallower than 10 km, the study area holds geothermal resource potential, particularly in the North-central region. The correlation between estimated spectral depths from aeromagnetic data and observed geothermal signatures in the study area promises to be advantageous in the pursuit of alternative energy generation, potentially mitigating the effects of global warming.

Petrogenesis and Tectonic Implications of the Early Triassic Nianzi Adakitic Granite Unit in the Yanshan Fold and Thrust Belt: New Constraints from U‐Pb Geochronology and Sr‐Nd‐Hf Isotopes

AbstractThe Nianzi granite unit, which includes the Nianzi, Xiaolianghou and Xiawopu granitic intrusions, is a significant component of the northern part of the North China Craton (NCC) and is situated in the Yanshan fold and thrust belt (YFTB). However, there is still debate regarding the tectonic evolutionary history of the YFTB during the late Permian to Triassic period, specifically regarding the timing of subduction and collision between the NCC and the Paleo‐Asian Ocean. The Nianzi granite unit exhibits unique petrological, geochronological and geochemical signatures that shed light on the tectonic evolutionary history of the YFTB. This study presents detailed petrology, whole‐rock geochemistry, together with Sr‐Nd isotopic, zircon U‐Pb dating and Lu‐Hf isotopic data of the granites within the Nianzi granite unit. Our findings demonstrate that the granites primarily consist of subhedral K‐feldspar, plagioclase, quartz, minor biotite and hornblende, with accessory titanite, apatite, magnetite and zircon. Zircon U‐Pb dating indicates that the Xiaolianghou granite was emplaced at 247.5 ± 0.62 Ma. Additionally, the adakitic characteristics of the Nianzi, Xiawopu and Xiaolianghou granitic intrusions, such as high Sr and Ba contents and high ratios of Sr/Y and (La/Yb)N, combined with negative Sr‐Nd and Lu‐Hf isotopes (87Sr/86Sr)i = 0.705681–0.7057433, εNd(t) = –21.98 to –20.97, zircon εHf(t) = –20.26 to –9.92), as well as the I‐type granite features of high SiO2, Na2O and K2O/Na2O ratios, enriched Rb, K, Sr and Ba, along with depleted Th, U, Nb, Ta, P and Ti, suggest that the Nianzi granitic unit was mainly derived from the partial melting of a thickened lower crust containing hydrous, calc‐alkaline to high‐K calc‐alkaline, mafic to intermediate metamorphic rocks. In light of these parameters, we further integrate our data with previous studies and conclude that the Nianzi granitic unit was generated in a post‐collisional extensional environment during the Early Triassic.

In situ analysis of mica from the Daguanshan granites in Western Yunnan: Implication for Sn enrichment and mineralization

The potential of tin mineralization associated with the Triassic Lincang granite batholith in Western Yunnan, China, has been poorly understood, despite the batholith being considered the northern extension of the Southeast Asian Tin Belt. To address this issue and gain insights into the mechanism of tin enrichment, we investigate the major and trace element compositions of biotite and muscovite from four granite units in Daguanshan, including hornblende-biotite granite, biotite granite, two-mica granite, and muscovite granite in the Hongmaoling Sn deposit. From the hornblende-biotite granite to two-mica granite, the biotite composition varies from Mg-biotite to Fe-biotite with increasing MnO and decreasing K/Rb. The Fe3+-Fe2+-Mg2+ diagram and decreasing Mg/(Fe + Mg) ratios of the biotite indicate reducing conditions. From two-mica granite to muscovite granite, the muscovite Li, F, Rb and Cs concentrations generally increase with decreasing K/Rb, suggesting a magmatic fractionation trend. The variations in zoned muscovite composition reflect a high degree of magmatic fractionation and a lack of fluid interaction. Biotite tin concentrations increase from ∼ 18 ppm in the hornblende-biotite granite to ∼ 36 ppm in the biotite granite and further to ∼ 62 ppm in the two-mica granite. In addition, tin concentrations increase from ∼ 180 ppm in the core to ∼ 330 ppm in the rim of muscovite in the muscovite granite. These data indicate that magmatic fractionation is critical to Sn enrichment in the Hongmaoling deposit. The Nb/Ta ratio and tin concentration in mica from tin mineralized granites are generally higher than those from barren granites, indicating they could be used as reliable indicators for assessing tin metallogenic potential.

Transport of Magma in Granitic Mush Systems; an Example From the Götemar Pluton, Sweden

AbstractGranitic magma bodies form in the ephemeral part of magma mush systems and are emplaced by a variety of mechanisms in different tectonic settings. This study investigates how granitic magma emplacement processes and tectonomagmatic interactions assert control over the architecture of mush state pluton‐scale magma transport pathways. The 1.45 Ga shallow‐crustal Götemar pluton is a 4.5 km diameter circular pluton that consists of three granite units: a coarse‐grained red granite, a medium‐grained pale to red granite, and fine‐grained pale microgranite sheets. We employed geological mapping supported by Anisotropy of Magnetic Susceptibility (AMS) to examine the magmatic and regional tectonic controls on late‐stage magma transport in the Götemar granitic magma mush system. Multiple parallel arcuate subhorizontal microgranite and medium‐grained granite sheets (from 0.1 to 10s of meters thick) were mapped within the pluton. The arcuate sheets pinch out from the northern part of the pluton toward the SE inferring magma propagation direction. A dominant set of vertical granitic sheets within the granite body strikes NW‐SE. The AMS fabrics are contact‐parallel in the main medium‐grained granite body and indicate inflation. Within the microgranite sheets, the AMS fabrics are parallel to the sheet strike and support a sheet propagation direction to the SE. The Götemar pluton displays a clear link between arcuate (concentric) magma‐transporting sheets and concentric strain‐partitioning related to the intrusion of medium‐grained granite magma. The vertical magma sheet orientations are consistent with an NE‐SW extensional stress field that is associated with the extensional back‐arc stress regime of the contemporary Hallandian Orogen.

Li-rich pegmatites and related peraluminous granites of the Fregeneda-Almendra field (Spain-Portugal): A case study of magmatic signature for Li enrichment

Based on field and petrographic observations, mineralogical, geochemical (whole-rock by ICP-MS, ICP-OES, ISE and PGNAA) and geochronological (ArAr on mica and UPb on columbite) data, ten pegmatite types and one type of cassiterite-rich quartz hydrothermal veins have been distinguished in the Fregeneda-Almendra field (FA) (Central Iberian Zone), some of them highly enriched in Li (included in petalite, spodumene and Li-rich mica). The pegmatites and the veins mostly intrude Neoproterozoic to Cambrian rocks from the Schist-Greywacke Complex. Felsic igneous magmatism during syn- to late-D3 stages (≈ 320–295 Ma) of the Variscan orogeny was important and nearly continuous in the area, with the overlap of different granitic units of highly peraluminous S-type composition. The most important in outcrop corresponds to the Mêda-Escalhão-Penedono-Lumbrales granitic complex (MEPL), which belongs to a two-mica leucogranitic series. The other granitic units (Saucelle, Feli and East-MEPL granites) are younger and belong to a P-rich, Ca-poor monzogranitic series. Spatial relationships, together with chemical, mineralogical and geochronological data, indicate that all the pegmatite types and the cassiterite-rich quartz hydrothermal veins are not cogenetic, being related to three different magmatic events: (i) (≈ 319–313 Ma) includes the syn-D3 MEPL granite and three types of barren pegmatites (intragranitic, quartz+andalusite layers and simple concordant pegmatites); (ii) (≈ 305–300 Ma) corresponds to the late to post-D3 Feli granite, related to a group of cassiterite-rich quartz veins; and, (iii) (≈ 300–298 Ma) represents the late- to post-D3 East-MEPL and Saucelle granites, likely parental of some barren aplitic-pegmatitic apophyses and the discordant intermediate and Li-rich pegmatites. These latter form part of a general granite-pegmatite fractionation trend.

Mineralización de afinidad granítica en la porción central del batolito de Colangüil. Provincia de San Juan, Argentina

The central portion of the Batholith of Colangüil belongs to the Frontal Range and is located in the northwest of San Juan province, Argentina. It includes different granite units of Permian in age: Romo, Conconta, and Agua Blanca. These intrude the Cerro Agua Negra Formation, an Upper Carboniferous - Asselian sedimentary unit. These units are partially covered by volcaniclastic rocks of the Choiyoi Group, lower Permian-Triassic in age. The region was characterized by mineral extractions during the last century. Metalliferous mineralization has been recognized in the higher elevation areas of the Conconta and Agua Blanca plutons, with an early paragenesis of wolframite, fluorite, niobium, and quartz, and later deposition of scheelite, in quartz gangue. The latter was observed in the Agua Blanca pluton. The tectonic of the Cisuralian Permian San Rafael phase, compressive in nature, affected mainly the Cerro Agua Negra Formation. An oriented NW-SE fault array on the aforementioned igneous and sedimentary units stands out. Two regional fracturing axes limit laterally this sector of the batholith and match the location of the mineral deposits. A greater ascent of granite basement blocks can be seen to the south of the Conconta pluton and in the surroundings of the Agua Blanca pluton, based both on the intense erosion of its sedimentary host rock and by the little development of mineralization in the Romo sector. The fluid inclusion assemblages present in the veins of the Conconta and Romo sectors are linked with saline and carbonic fluid types, typical of the tungsten deposition cycle.

The Amaros and Dois Córregos plutons: Mesoarchean and Orosirian magmatism in the northern Guanhães basement inlier, Araçuaí orogen, Brazil

In this paper we present new field, geophysical, petrographic, geochemical and geochronological data from granitic rocks newly recognized at the northern Guanhães block, one of the basement inliers of the Araçuaí orogen, eastern South America. Our data allowed the identification of two granitic units, namely Amaros and Dois Córregos plutons, intrusive in the Archean orthogneisses of the Guanhães Complex. In the studied area, the Guanhães Complex comprises muscovite-biotite gneisses, hornblende-biotite gneisses and clinopyroxene-hornblende-biotite gneisses. These rocks have distinct chemical characteristics, which range from TTG series to Late Archean hybrid granitoids. The Amaros pluton is composed of muscovite-bearing biotite metasyenogranites. These rocks are high-K calc-alkaline, magnesian and peraluminous, and were interpreted as a product of partial melting of an older TTG crust. U–Pb ICP-MS dating of zircons yielded a crystallization age of 2916 ± 19 Ma for Amaros pluton, which makes it the first Mesoarchean granite pluton delimited and detailed within the Guanhães block. Mesoarchean magmatism (ca. 2.9 Ga) similar in composition to the Amaros pluton is well known at the Porteirinha block, another basement inlier to the north of the Guanhães block, which raises questions about a connection between the two domains. The Dois Córregos pluton, firstly identified through geophysical analysis, is composed of hornblende-bearing biotite syenogranite crystallized at 2045.5 ± 24 Ma Ma (U–Pb in zircons, ICP-MS). These rocks are alkali-calcic to alkalic, magnesian to ferroan, ranging from per-to metaluminous and were interpreted as a product of the partial melting of continental crust, in a late-collisional stage of the Minas-Bahia orogeny, during the amalgamation of São Francisco-Congo paleocontinent.

Intra-granitic pegmatites of the Las Chacras-Potrerillos batholith (Sierra de San Luis, Argentina): Geochemistry, dating, and a new model of magma evolution

The chemical composition of primary minerals and fine-grained border zones from intra-granitic pegmatites have been analyzed to constrain the last stages of magmatic differentiation in the Devonian Las Chacras-Potrerillos batholith, central Argentina. Based on accessory phase assemblages and mineral chemistry, the pegmatites are assigned to the NYF (Nb – Y – F) family. They were emplaced in all six units of the batholith but there is an increase in pegmatite abundance, size and complexity from north to south in the batholith. A similar N–S trend in pegmatite melt evolution is defined by fractionation indicators in pegmatitic K-feldspar (e.g., K/Rb: 68–301, Rb/Sr: 1–47, Cs: 8–71 ppm, Ba: 66–800 ppm), in white mica (e.g., K/Rb: 36–99, Rb/Sr: 40–826, Cs: 30–206 ppm, Ba 18–1889 ppm) and in tourmaline (Fetot + Mgtot: 2.6–4.0 apfu, Altot: 5.0–6.4 apfu). The regional fractionation patterns of pegmatite mineral chemistry are consistent with a general southward increase in the fractionation degree of the host granite units, confirming that compositional characteristics of the parental magmas are passed on to the pegmatitic phases. A new zircon U–Pb age of 388.3 ± 1.9 Ma from the southern granites constitutes the oldest crystallization age of the batholith. This resolves the previously-debated emplacement sequence and has important implications for the magmatic evolution of the largest and most evolved pegmatites, which cluster around the contact zone between the southern granites and the younger, central unit (biotite porphyritic granite). The age constraints combined with chemical data from the pegmatitic minerals show that pegmatites in the southern region of the batholith share a common magma source, which we suggest is the central unit of biotite porphyritic granite. The increased degree of fractionation in the southern pegmatites is attributed to elevated concentrations of volatiles in the parental magmas, which derive from dehydration partial melting and assimilation of fluids from metaclastic rocks in the crust.

Geology and Geophysics of Talumopatu Geothermal Manifestation Area of Mootilango District, Gorontalo Regency, Indonesia

The research aims to assess the geothermal potential and provide a better understanding of the geology and geophysics of the area. The study utilizes various methods, including geological mapping, geochemical analysis, and magnetic and electromagnetic data analysis, to gain insights into the subsurface structures and characteristics of the geothermal system. The study area can be divided into three geomorphological units: Alluvial Plain Unit, Near Plains Unit, and Isolated Hill Unit. The study area exhibits a stratigraphy consisting of three primary units: Talumopatu granite units, Talumopatu sandstone units, and alluvial deposit units. The subsurface lithologies of the Talumopatu manifestation area were analyzed using the Wenner – Alpha configuration ERT method, revealing two distinct lithologies. The first lithology consists of sandstones with a resistivity value ranging from 4.2 to 39.0 Ωm and a thickness of 1.25 to 12.4 m, which act as a permeable layer capable of transmitting water. The second lithology is granite with a resistivity value ranging from 118 to 360 Ωm and a thickness of 3.75 to 15.9 m. This information provides valuable insights into the subsurface characteristics of the area, including the presence of permeable layers and the geological composition of the lithologies

Combined ERT and borehole logs for mapping the soil-rock interface in a granitic environment

This study used the efficiency of electrical resistivity tomography (ERT) and borehole logs to map the soil-rock interface beneath four traverses (RS1, RS2, RS3, and RS4) in the granitic terrain of Perak, Peninsular Malaysia. The study aimed to evaluate the impacts of the soil-rock characteristic features and interfaces on groundwater and infrastructure development to meet the needs of the increasing inhabitants yearly. The borehole- and ERT-derived lithologic units are strongly correlated. The delineated lithologic units include the topsoil, weathered granitic units (medium stiff to hard silty clay or clayey silt with <800 Ωm), thin to wide-sized weathered/fractured units, and fresh granitic bedrock. These soil-rock profiles and weathered/fractured apertures support sustainable groundwater developments with drill depths above 45 m. In contrast, the delineated clay/silt alternating with stiffer soils, low load-bearing deep-weathered/fractured zones, and bedrock boulders in most places, except beneath traverse RS3, have high affinities for water retention and differential stresses. These features can adversely impact poorly reinforced foundations. Hence, structural elements of the foundations, such as footings or piles, should be placed on stable bedrock, particularly in the central to western parts of the study area. This study has reduced the paucity of information on using ERT and borehole logs for soil-rock interface studies in the study area.

Ergonomic risk assessment of tasks performed by workers in granite and marble units using ergonomics tool’s REBA

Mining industry, of which the marble, granite and stone market is one such high performing sector. among the various high performing sectors in the Indian economy. Musculoskeletal disorder’s [MSD’s] are a major concern in industries. MSD’s are the predominant factors,leading to injuries and disability in many industries. Adverse working postures of the employees exposed risks levels of injury and that of the hazard. MSD’s risk factors shall be assessed in order to plan and implement ergonomics intervention awareness among the workers so as to minimize work-related health risks in these sectors by identifying potential risks that may lead to injury or musculoskeletal disorders in a marble and granite units. The intent of the current research work is to recognize innumerable MSD’s of the labourer involved in this sector. The procedure was initiated with a workplace observation followed by simple questionnaire among twenty-five operators.The working activities of these workers were recorded from which images were taken for analysis. The assessment shall be organized at the initial stage as well as at later stage to address that the ergonomic intervention has worked out successfully in reducing the possibility of injuries and MSD’s risk factors. The result reflects that more than ninety percent of the employees were suffering from high levels of risk and needs quick change. The researcher proposed ergonomically designed new workstation to reduce injuries & WRMSD’s to an acceptable level with awareness and ergonomic training to workers.

Compositional Variations in Apatite and Petrogenetic Significance: Examples from Peraluminous Granites and Related Pegmatites and Hydrothermal Veins from the Central Iberian Zone (Spain and Portugal)

Apatite can be used as an archive of processes occurring during the evolution of granitic magmas and as a pegmatite exploration tool. With this aim, a detailed compositional study of apatite was performed on different Variscan granites, pegmatites and quartz veins from the Central Iberian Zone. Manganese in granitic apatite increases with increasing evolution degree. Such Mn increase would not be related to changes in the fO2 during evolution but rather to a higher proportion of Mn in residual melts, joined to an increase in SiO2 content and peraluminosity. In the case of pegmatitic apatite, the fO2 and the polymerization degree of the melts seem not to have influenced the Mn and Fe contents but the higher availability of these transition elements and/or the lack of minerals competing for them. The subrounded Fe-Mn phosphate nodules, where apatite often occurs in P-rich pegmatites and P-rich quartz dykes, probably crystallized from a P-rich melt exsolved from the pegmatitic melt and where Fe, Mn and Cl would partition. The low Mn and Fe contents in the apatite from the quartz veins may be attributed either to the low availability of these elements in the late hydrothermal fluids derived from the granitic and pegmatitic melts, or to a high fO2. The Rare Earth Elements, Sr and Y are the main trace elements of the studied apatites. The REE contents of apatite decrease with the evolution of their hosting rocks. The REE patterns show in general strong tetrad effects that are probably not related to the fluids’ activity in the system. On the contrary, the fluids likely drive the non-CHARAC behavior of apatite from the most evolved granitic and pegmatitic units. Low fO2 conditions seem to be related to strong Eu anomalies observed for most of the apatites associated with different granitic units, barren and P-rich pegmatites. The positive Eu anomalies in some apatites from leucogranites and Li-rich pegmatites could reflect their early character, prior to the crystallization of feldspars. The increase in the Sr content in apatite from Li-rich pegmatites and B-P±F-rich leucogranites could be related to problems in accommodating this element in the albite structure, favoring its incorporation into apatite. The triangular plots ΣREE-Sr-Y and U–Th–Pb of apatites, as well as the Eu anomaly versus the TE1,3 diagram, seem to be potentially good as petrogenetic indicators, mainly for pegmatites and, to a lesser extent, for granites from the CIZ.

Characteristics and rippability conditions of near-surface lithologic units (Penang Island, Malaysia) derived from multimethod geotomographic models and geostatistics

The nature and rippability conditions (rock mass quality [RMQ]) of the near-surface lithologic units of Batu Maung, Penang Island, Malaysia, were investigated to develop sustainable groundwater and infrastructure. This study used a novel approach that combined seismic refraction tomography (SRT), electrical resistivity tomography (ERT), borehole drilling, and simple linear regression (SLR) analysis. The seismic P-wave velocity (Vp) and resistivity models revealed four distinctive units: residual soils (silty sand), very poor-to-good (weathered) granite, and the fresh granitic unit, including the fractured/faulted zones. The thicknesses of the residual and weathered materials ranged from a few centimeters to 15 m and 1.0–16 m, respectively. The developed empirical relationship effectively predicted rock quality designation (RQD) from Vp data through SLR analysis, with a prediction accuracy of 96% and a p-value<0.05. Also, the results from five key regression assumptions: linear relationship, multivariate normality, no multicollinearity, no autocorrelation, and homoscedasticity, suggested an accurate and statistically significant empirical relationship for use in granitic environments. The RMQ statistical model accurately classified the lithologic units beneath the area into Classes I–VI. Due to the low load-bearing of the rippable residual soils, very poor-to-fair weathered granitic rock masses, and fractured/faulted zones based on their Vp and resistivity values, and the steep slopes in the northern section of the study area, all intended infrastructures, particularly high-rise buildings and buildings with continuous footing foundations, should be piled to rest on the non-rippable fresh granitic units, with RQD and Vp values of >90% and >2100 m/s, respectively, in the central to the northcentral section in the study area. Conversely, the deep-weathered/fractured zones of depths >35 m, beneath Line 1, towards the central part of the area, with resistivity and Vp values of 100–900 Ω-m and <1900 m/s, respectively, were identified as potentially water-containing zones for sustainable groundwater abstraction.

From metamorphic core complex to crustal scale rollover: Post-Caledonian tectonic development of the Utsira High, North Sea

The Utsira High (North Sea) records rift faulting that culminates with Jurassic-Cretaceous crustal-scale rollover towards the Viking Graben. This deformation is superimposed on Paleozoic fault-bounded basins on a substrate of Caledonian nappes. The latter contains multilevel crustal-scale shear systems that domed under the Utsira High during the Devonian, as indicated by mapping and interpretation of a large long-offset 2D seismic reflection dataset. Restorations show that isostatically driven doming from excision of overthickened crust caused uplift and erosion of basins and the underlying nappe stack. Doming took place above a crustal rollback system as a symmetrical metamorphic core complex formed. The dome discloses vertical flattening kinematics below bi-directional shear systems, evident by opposite shear-fabric kinematics on opposite dome flanks. A major detachment marks the upper boundary of a transition between upper and lower plate strain regimes, coinciding with low-reflective granitic units above strongly reflective Caledonian nappes. This detachment hosts transport-parallel corrugations that strike E-W to NE-SW. A series of deeply eroded half-grabens on top of the upper plate are bounded by pre-Permian faults exhibiting top-NE extensional kinematics. Faults sole out in the fundamental detachment level, locating the brittle-ductile transition, with all structures subsequently rotated during doming. A new localized detachment formed at a shallower level above the region of maximum crustal uplift, seen as upwards detachment migration driven by heating. Later faulting locates to the dome flanks, either rejuvenating rotated shear zones or cutting to deeper crustal levels while recording predominantly down-eastward transport. During Jurassic-Cretaceous rifting, deformation localized to the Viking Graben Boundary Fault, giving room for thick growth wedges in the Viking Graben and establishing the Utsira High as a crustal-scale rollover structure.