Intrusive Bodies Research Articles

Ore textures and chemical constraints in the Serantak goldfield, northwest Borneo, Indonesia: implications for retrograde skarn occurrences

The ore characteristics and geochemistry at the Serantak goldfield are pivotal for understanding the genetic model of the gold mineralisation. This study focuses on identifying textures, compositions and their elemental associations, which are key parameters for ore-forming processes. Research involved fieldwork, sampling, petro-mineragraphy, rock geochemistry analyses and modelling. The results demonstrate a distinct ore genesis and sequence, classified into retrograde skarn and epithermal vein styles. Syngenetic gold skarn types dominate in the proximal zone, exhibiting minerals like pyroxene ± garnet ± wollastonite–epidote–calcite, alongside disseminated sulfides such as pyrite–pyrrhotite–chalcopyrite, are confined within meta-sedimentary units in the northeast-trending intercalated bedding. Gold is associated with arsenic ± silver ± copper. In later stages, within the peripheral zone, epithermal veins develop along fractures within major reactivated northwest structures and dilatational jogs, marked by quartz–feldspar ± sericite ± chlorite hosted in volcaniclastic rocks and associated with pyrite ± arsenopyrite ± realgar. At this stage, gold shows a strong correlation with silver ± arsenopyrite. Meteoric water re-equilibration triggers a supergene enrichment process linked with manganese-jarosite ± hematite minerals. Exploration efforts in the vicinity of intrusive body and delineation of continuity vein-style mineralisation are also critical for upside potential, while additional studies on mineral chemistry and gold deportment are needed.

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.

Delineating Structural Features Related to Hydrothermal Alterations for Possible Mineralization in Share Area, Kwara State Nigeria Using Aeromagnetic Data

Mineral deposits of significant economic value are abundant in the subsurface of Nigeria, presenting a promising alternative to the nations over dependence on petroleum revenues. This study interprets aeromagnetic data from Share, Kwara State, Nigeria, to delineate subsurface structural features associated with hydrothermal zones, which are key indicators for potential mineralization. The methodologies applied upward continuation, analytic signal, tilt derivative, and first vertical derivative (FVD). These offer insights into subsurface geology that can be broadly applied in geophysical exploration and mineral resource management. The results reveal structural trends predominantly in the NE–SW direction, with some NW–SE alignments, indicative of hydrothermal alterations linked to mineral deposits. The analytical signal map identified amplitude values ranging from 0.004 nT/m to 0.073 nT/m, with low and intermediate magnetic intensities linked to sediment-filled basement rocks and possible limestone and sandstone formations. High-gradient anomalies, 1.280 nT/m to 1.374 nT/m, were attributed to geological contacts, fractures, dykes, and hydrothermal vents. Depth estimates from the source parameter imaging map revealed hydrothermal and structural zones at depths ranging from 287.9 m to 1360.7 m, with deeper sources >1202.1 m indicating tectonic activity and mineralization potential. The FVD and Tilt Derivative maps further highlighted faulted zones, shear structures, and intrusive bodies with intensities between 0.031 nT/m and 0.041 nT/m, suggesting active tectonics. High magnetic anomalies in the central, northeastern, and southeastern regions were identified as prime targets for exploration, indicating magnetite-rich bodies, igneous intrusions, and hydrothermal zones. Integrated exploration strategies combining geophysical, geochemical, and structural data are recommended to refine anomaly delineation, prioritize field validation, and enhance mineralization discovery. These findings establish the Share area as a promising site for regional mineral exploration, supporting Nigeria’s diversification efforts toward sustainable resource development.

Условия образования месторождений золота золоторудно-кварцевого формационного типа на примере рудопроявления Хугланнах Верхояно-Колымской складчатой области

The Hooglannah ore deposit is located on Ayan-Yuryakh anticlinory territory of the Verkhoyansk-Kolyma folded region. There are unexplored gold ore manifestations of the gold-ore-quartz formation, as well as industrial and non-industrial placers of gold. The distribution area of gold mineralization within the Hooglannach ore occurrence is localized in the dyke-like body of granodiorite porphyries and in its exocontact. The host rocks are the Atkan and Omchak formations deposits of Late Permian age, collected in a brachysynclinal fold. An intrusive ore-controlling body is confined to its axial part. Rocks containing volcanogenic material take part in the structure of the host complex: tuff sandstones, tuffoaleurolites, tuffoargillites, tuffogenic mixtites, as well as la voxtites, tuffs and tuffites of andesite and dacite. The veined-interspersed type is the leading structural and morphological type of mineralization. The vein-veined type occurs rarely. Ore mineralization is represented by thin inclusions of arsenopyrite, galena, and gold, which is usually confined to dark gray stripes in the band parts of veins. The conducted mineralogical and petrographic studies have established that the rocks of the intrusive body of granodiorite porphyry accompanying the Hooglannach stock were subject to processes corresponding to high-temperature autometasomatosis and mesothermal near-crack metasomatosis by the type of berezitization. This type associated with the hydrothermal stage of gold-quartz ore formation. The multifactorial model of the Hooglannah ore occurrence was formed, based on the obtained material.

Тhermal history and fluid regime during the formation of Eldjurta massif of biotite granites (Greater Caucasus): reconstructions based on isotope (δ<sup>18</sup>О, δD) and geochemical data

Based on the geochemical and isotopic (δ18О, δD) data the thermal and fluid conditions during the formation of the Eldjurta granite massif were reconstructed. Analysis of rocks collected from the core of the Tyrnyauz Superdeep Well (TSW) within the depth range of 1427–3923 m revealed their homogeneous isotopic parameters: the δ18О values of bulk samples, quartz, feldspars, and biotite in 12 samples of biotite granites are 8.50 ± 0.33, 9.55 ± 0.22, 8.40 ± 0.33 and 5.45 ± 0.40‰, respectively. The δD values in the biotite vary from −103.3 to −95.6‰. The closure temperatures of the oxygen isotope system of quartz are 440–980°C. The rock cooling history was reconstructed using a new approach based on the analysis of single quartz grains. This approach can be used for detailed reconstructions of thermal history during formation of intrusive bodies. The definite samples were used to demonstrate that Dodson’s equation is valid for description of the δ18О values of quartz in a granite system. The data obtained suggest that the studied part of the massif was formed in at least two almost simultaneous stages. The lower part of the massif was crystallized first, and the second injection of granite melt arrived immediately after the first portion has been crystallized, but had no yet had time to cool significantly. The Тс values in the lower part of the massif indicate the reopening of the oxygen isotope system of quartz, with subsequent long-term isotope re-equilibration between minerals. This leads to decrease of the observed Тс values and the calculated cooling rates, which is related to increasing volume of the intrusive body and cooling within already heated rocks. Estimates of the isotopic parameters of the water component indicate the absence of exotic water fluid (meteoric or buried waters) during cooling of the massif. The variations of the δ18О values in the minerals of the Eldjurta biotite granites can be described only in terms of a simple retrograde exchange at the cooling stage

Geotourism Potential of Curug Jompong, Jelegong Village, West Bandung Regency

Abstract Bandung City is a part of Bandung Basin with surrounded by hills. On the western edge of the basin, there is a steep hill ridge stretching from north to south, cut by a narrow valley, the Citarum River Valley, where Curug Jompong is located. This is the site where the Ancient Bandung Lake breached. The aim of this study is to understand why the Ancient Bandung Lake breached at this location. The results can be used to develop the Curug Jompong Area into a geotourism destination. The methodology involves observing landforms, lithology, geological structures, petrography, XRD, and chemical analysis, and drones mapping. In the research area, the drainage pattern is shaped by intense joints, faults from tectonic activity and magma cooling process. The lithology is composed of andesite intrusions, which are typically resistant to erosion. The intrusion body has undergone phyllic alteration with alteration minerals such as chlorite, calcite, kaolinite, illite, montmorillonite, quartz, and albite. The fault and joint structures, as well as the intensively developed phyllic alteration in Curug Jompong, have reduced the resistance of igneous rocks to erosion, resulting in the formation of the Citarum River valley, which drained water from the Bandung Basin, draining the Ancient Bandung Lake. Thus, this unique geological feature of the Curug Jompong may have potential for geotourism development in the West Bandung Regency

Imaging upper lithospheric structures of the Benue Trough and adjoining basement areas in Nigeria and Cameroon from satellite gravity data

This study investigates the structures of upper lithosphere in the Benue Trough (BT) and its abutting basements in Nigeria and Cameroon through detailed analyses and interpretation of satellite Bouguer gravity anomaly (BA) data. Matched bandpass filtering, edge enhancements (tilt- and theta-derivatives), 3D inversion, and 2D modelling methods were applied to the BA data. The result from matched bandpass filtering reveals four gravity layer sources with their respective average depths, namely near-surface geological bodies (c. 0.6274 km), depth to basement (sediment thickness; c. 5.8921 km), intra-crustal boundary (c. 12.7538 km) and Moho (c. 27.980 km). Tilt- and theta-derivatives of the BA imaged numerous regional tectonic fabrics/structures exhibiting ENE – WSW, NNE –SSW, and NE – SW major trends coupled with N – S, NW – SE and E − W minor trends across the area, with the major regional tectonic trends mostly dominant in the BT and Adamawa Plateau/Cameroon Volcanic Line (AP/CVL) regions. Positive tilt cum positive theta derivatives of BA indicate that high-density (dense) geological bodies occur within the underlying sediments and crustal basements, particularly within the BT. 3D inversion result reveals a conspicuous and elongated (c. > 600 km long, 120 km wide) NE – SW orientated shallow (c. 23–30 ± 3 km) Moho structure beneath the BT and a prominent elongated, large (c. > 550 km long, 115 km wide) NE – SW striking deep (c. 34–44 ± 3 km) Moho structure below the AP/CVL region in the Western Cameroon Domain/Adamawa-Yade Domain (WCD/AYD) of Cameroon. Also, it shows that the Northern Nigerian Basement Complex (NNBC) and Eastern Nigerian Basement Complex (ENBC) regions are characterised by highly variable Moho morphology and depths (c. 26 to 36 ± 3 km). Generated 3D Moho model represents the first detailed Moho model for this studied area. The result from 2-D forward modelling of a NW – SE representative profile, constrained by known outcrop regional geology and available nearby seismic/teleseismic information, indicates the presence of two variable sedimentary sub-basins (c. 2–5 ± 0.4 km deep), a basement ridge and shallow Moho (c. 23–27 km ± 2 km) in BT region with occurrences of shallow intrusive bodies (e.g. granites), dense lower crustal body and deep Moho (c. 30–40 ± 2 km) underneath the basement regions, particularly in the AYD region. It also highlights that the underlying crust in BT is thinnest while thickest in basement regions of NNBC, ENBC, WCD (particularly AP/CVL area) and AYD along the NW – SE profile. The Moho depth values obtained in this study are within ±3.5 km with all those previously published from teleseismic works in the studied area. The imaged major NE – SW and ENE –WSW orientated tectonic fabrics/structures of the Precambrian crustal basement may have strongly influenced the location, emplacement and orientations of the BT, AP/CVL and Younger Granite complexes. Also, the BT developed in response to mechanical stretching (extension) of the lithosphere driven by regional far-field extensional stresses originating from remote plate tectonic/boundary forces coupled with some active-related effects (e.g. thermal upwelling of mantle materials) caused by changes in the dynamics of the sub-lithospheric mantle during the rifting in the Jurassic – Cretaceous.

Igneous reasons why porphyry Cu–Au deposits are not magmatic

The presence or absence of porphyritic textures in host rocks has no meaning for the genesis of ‘porphyry’ deposits. ‘Magmatic’ quartz, intergrown with K-feldspar and associated with some porphyry mineralisation, is unequivocally hydrothermal. Experiments show that magmas cannot carry concentrations of Cl required to yield fluids that can deposit the metals in porphyry Cu–Au deposits, and this is substantiated by the Cl concentrations in fluid inclusions in both mafic and silicic igneous rocks. Other experiments show that magmas generally have lower Cu concentrations than average crustal rocks. Igneous fractionation cannot produce melts with the required Cl or metal contents. Experiments also show that, if highly saline brines (or halite deposits) were to have been present during crustal melting, the magmas produced would have mineralogical and chemical characteristics most unlike the rocks that commonly host porphyry mineralisation. The metals in porphyry deposits must come from the medium- to far-field wall rocks and were most likely precipitated in veins when the host rocks underwent brittle fracture and fluid decompression. While still cooling, completely solid intrusive bodies can act as thermal eyes in a terrane, setting up hydrothermal circulations with flow toward the intrusions and upward toward shallower levels. The idea that precursor batholiths might be responsible for the supply and concentration of metals and Cl is untenable for numerous reasons. What applies to shallow igneous systems also applies to deeper ones. Thus, if magmas cannot carry the required concentrations of Cu and Cl, this applies to the seen as well as the unseen and potentially non-existent. Economic mineral deposits everywhere represent exceptional phenomena, so it seems likely that there is also something systematically exceptional about the sources of the necessary Cl in fluids that form porphyry deposits. At present, that source remains unidentified, but the possible role of evaporitic rocks needs to be explored.

Triassic–Jurassic alkaline magmatism in the Ivrea-Verbano Zone, Southern Alps: A zircon perspective on mantle sources and geodynamic significance

The Ivrea-Verbano Zone (IVZ; western Southern Alps) consists of a distinctive sequence of the lower continental crust of the Adriatic plate, extending down to the subcontinental lithospheric mantle. It is characterized by a large variety of intrusive bodies of variable geochemical composition and age, offering a unique insight into the evolution of mantle-derived magmatism in post-collisional and extensional geodynamic settings. In this study, we characterize a suite of alkaline dykes intruding a mantle massif – the Finero Phlogopite Peridotite in northern IVZ. These dykes include zircon-bearing diorites and anorthosites, mainly composed by HFSE-rich amphibole and phlogopite, albite (>90 vol% in anorthosites) and apatite. Zircon, monazite, ilmenite, titanite, Nb-rich oxides, and carbonates are common accessory minerals. Additionally, a “composite” diorite dyke containing both HFSE-rich and HFSE-poor amphiboles was investigated. The study is aimed at providing new trace element, U-Pb geochronological and Lu-Hf isotopes dataset on zircon from these alkaline dykes, to refine the understanding of their mantle source characteristics, emplacement age and geodynamic implications. The trace element composition of zircons from the studied dykes points to segregation from melts with alkaline to ultra-alkaline affinity. Concordia U-Pb ages of zircon from the alkaline diorite dykes span from 221 to 191 Ma, which are interpreted as the result of multiple crystallization/recrystallization stages related to different magmatic pulses. Conversely, zircon from anorthosite and composite diorite dykes yield a narrow time range of 198–202 Ma, highlighting the occurrence of a magmatic pulse around ca. 200 Ma. The εHf(t) values (+13.4 to +5.7) of zircon from the alkaline diorite dykes are significantly more positive compared to the values in those from anorthosite and composite diorite dykes (+4.2 to −0.4), suggesting that the parental melts were derived from heterogeneous asthenospheric mantle sources with low to moderate amount of recycled continental crust components. Our data and reappraisal of the literature indicate that the IVZ experienced a protracted period of alkaline magmatism from ca. 235 Ma to 185 Ma. The melts migrated along mantle shear zones during the Triassic-Jurassic lithospheric extension. Different pulses of alkaline magmatism were associated with relevant extensional tectonic stages recorded by the continental crust, presumably triggering a passive uplift of heterogenous asthenospheric reservoirs over a front of at least 500 km. This tectono-magmatic cycle is a precursor to the focused rifting stage which caused the opening of the Jurassic Alpine Tethys, enhancing Pangea fragmentation.

Gabbro of the mantle part of the ophiolite section in the Alapaevsky dunite-harzburgite-gabbro massif (Eastern zone of the Middle Urals)

Research subject. An intrusive body of gabbroids breaking through mantle peridotites (dunites and harzburgites) of the Alapaevsky ophiolite massif (Eastern zone of the Middle Urals). Methods. The contents of petrogenic elements were determined by the X-ray fluorescence method; the contents of rare and scattered elements were studied by the ICP-MS method. The age of gabbroids was determined by 147Sm-143Nd ID-TIMS by isotope dating. Results. The gabbro and their containing ultramafic rocks were established to be of almost the same age of about 580 Ма, which indicates their belonging to a single ophiolite association of the Vendian age. At the same time, the gabbroids of the Alapaevsky massif differ sharply from both isotropic and stratified gabbro of the crustal part of the ophiolite section, fragments of which are observed within the Eastern zone of the Middle Urals, in terms of a significantly reduced content of light REE, rare alkalis, barium, uranium and thorium, as well as the absence of Pb maxima on spider diagrams. Conclusions. The established features in the composition and intrusive occurrence of the gabbro of the Alapaevsky massif among mantle ultramafic rocks indicate that the studied rocks cannot be identified with gabbroids of the crustal part of the ophiolite association. This suggests that this rather large intrusion of gabbro may be analogous to small veins and dikes of gabbroids observed among mantle peridotites in a number of ophiolite massifs, such as Voikar-Synyinsky massif in the Polar Urals and the Samail ophiolite in Oman. The distribution specifics of rare elements on the spider diagrams of the gabbroids of the Alapaevsky massif, i.e., the presence of Sr and Ba maxima and Nd and Th minima, as well as the Harzburgite composition of the mantle restite containing the gabbro body under consideration, indicate that the Vendian ophiolite association of the Eastern zone of the Middle Urals formed in a suprasubduction (pre-arc) environment. A model for the formation of large masses of gabbro in the mantle part of the ophiolite section is proposed.

Three-Dimensional Subsurface Model of Luk-Ulo Melange Complex, Karangsambung, Indonesia: Insights from Gravity Modeling

The Luk-Ulo Melange Complex (LMC) is characterized by a chaotic assemblage of mixed rocks with a block-in-matrix fabric. The exposed blocks consist of various scattered rock types, trending in an ENE-WSW direction. In the case of Mt. Parang, the origin of the diabase remains uncertain, with ongoing debate as to whether it is associated with in situ volcanic activity or represents an exotic block within the melange deposit. Subsurface data obtained through geophysical investigation can aid in modeling the geometry of intrusive bodies using inverse modeling techniques. In this study, we conducted a gravity survey and performed 3D inverse modeling to investigate the subsurface beneath Karangsambung. A total of 818 gravity data points and 28 rock density measurements were integrated with existing geological data to construct an a priori 3D geological model. To ensure the results align with geological concepts, the 3D inversion utilized a stochastic approach, allowing for the incorporation of multiple geological constraints over fifty million iterative procedures. Ultimately, the inversion successfully reduced the misfit between observed and calculated data from 2.71 to 0.55 mGal. Based on the inverted 3D model, the diabase rock in Mt. Parang is identified as having an intrusive origin. The intrusion model exhibited minimal changes in density, volume, and shape during the inversion process. Additionally, the model suggests the presence of a solidified magma reservoir at a depth of approximately 3 km, potentially related to Dakah volcanism. The inverted model also reveals the block-in-matrix structure of the Luk-Ulo Melange Complex in the northern area.

RECONSTRUCTION OF THE SUBSIDENCE DYNAMICS AND PALAEOTEMPERATURE REGIME OF THE NORTHERN MARGIN OF THE SIBERIAN PLATFORM

The formation mechanisms of sedimentary basins are considered as a response of deep processes in the mantle, therefore they carry important information about the geodynamics and thermal regime of the lithosphere. For different sectors of the northern margin of the Siberian Platform, the dynamics of sedimentation and subsidence was reconstructed. The analysis of subsidence curves shows that during the Late Paleozoic the sedimentary infill formed in the foreland basin environment. In the Late Permian–Early Triassic time, in the central and western sectors, the subsidence was accelerating due to the development of a thick trap complex; after the Permian and Triassic boundary the subsidence slowed down. During the period of trap magmatism, an anomalously high subsidence rate up to 4.8 km/Ma in the central and up to 0.5–1.1 km/Ma in the eastern and western parts was reconstructed. The high rate and short duration of accumulation of volcanogenic sediments can be explained by an episode of short-term extension under the influence of a plume, followed by a long period of thermal subsidence. Numerical modelling of the temperature regime near mafic intrusive bodies was carried out, which showed that when determining the paleoheat flow, the influence of trap intrusions can be traced up to 400–500 m from the contacts. Estimates of the paleoheat flow for the Permian–Triassic stage of tectonic evolution of the eastern sector were obtained. It was calibrated using the PetroMod software package, based on laboratory measurements of modern values of vitrinite reflectance for rock samples from wells, modern temperature and heat flow in the sedimentary cover. It was determined that trap magmatism occurred at temperatures increased to 100 mW/m2, while the mantle component of the heat flow reached 38–72 mW/m2; it is several times higher as compared to modern one. The obtained paleoheat flow estimates for the Late Permian–Early Triassic stage appear to correspond to anomalously high values of modern continental rifts.

Geology and geochronology of the El Peñón granitic pluton: A contribution to the famatinian magmatic evolution in the Sierra de San Luis, Argentina

The El Peñón pluton is a peraluminous granite located in the northeastern sector of the Sierra de San Luis. According to its textural and mineral variations two endmember facies have been distinguished along it: a coarse-grained muscovite-bearing facies, and a fine-grained biotite-bearing facies. Field relationships aligned with mineralogical and geochemical compositions, allow us to establish an anatectic origin for this pluton. Regarding the inherited zircon ages, the provenance area of the metasedimentary source could be linked to the orogenic systems of Western Gondwana. The analysis of the internal structure of the intrusive body related with the structural arrangement observed in the country rocks indicates a syn-kinematic emplacement of the igneous body with respect to the main deformational event described in the Sierra de San Luis, which has been assigned to the closure of the Famatinian arc. New U-Pb (LA-ICP-MS) zircon ages constrain the emplacement/crystallization age of the El Peñón granite within the time lapse between ∼470 and 460 Ma. The geochronological data presented here, together with geochemical and structural analysis, enables us to correlate the origin of the El Peñón pluton and the deformation that occurred during its emplacement with the Famatinian Orogeny. Thus, these results allow us to rule out the presence of Pampean magmatism in the Sierra de San Luis but also establish a new absolute age for the main deformational event of the range.

Mineralization characteristics of Lead-Zinc-Copper deposits in Akdağmadeni Region (Northern Central Anatolia, Türkiye): Integration of field study, geochemical, isotope, and geophysical data

The Akdağmadeni region is one of the important Pb-Zn-Cu metallogenic provinces in Türkiye. Most of the Pb-Zn-Cu deposits in the region are located near granitoid intrusions within metamorphic rocks, and they are typically classified as skarn-type ores associated with granitoids. However, no relationship has been determined between the Başçatak prospect and any granitoid outcrop. This raises the question of whether the Pb-Zn-Cu mineralization in the region is related to granitoids or if magmatic processes remobilized pre-existing mineralization. Observations from field studies suggest that mineralization in the Başçatak prospect is a stratiform type, metamorphosed occurrence that might have occurred earlier than the granitic intrusions. The geochemical data indicated that the granitoids have low-grade, subeconomic Cu potential and no Zn productivity potential, supporting these observations. Geophysical data also show that there is no intrusive body beneath this prospect. Granitoid-related deposits (Karapir - Ortaköy and Akçakışla) exhibit two distinct occurrences around the contact between the granite and the surrounding metamorphic rocks. The first type of occurrence (O-1) is formed at the contact and contains magnetite, pyrrhotite, and chalcopyrite. The second type of occurrence (O-2) is located outside the contact and is rich in sphalerite and galena. Both O-1 and O-2 contain skarn minerals along with ore minerals. The δ34S values of sulfide minerals from the deposits range from −0,7 to 7,5 ‰ (V-CDT). These values overlap with those of both magmatic sulfur and reduced sulfur from seawater-dissolved sulfate, making it difficult to suggest a sulfur source without additional data. Lead isotope compositions of the galenas from all deposits plot above the average crustal growth curve, suggesting an upper crustal and orogenic source similar to Western Mediterranean and Türkiye type materials described in the literature for the lead, source in different time intervals. Furthermore, Pb isotope geochemistry suggests a contemporaneous age with the host metamorphic rocks (Carboniferous – Lower Permian) for the Başçatak prospect. These results support observations indicating a syn-genetic formation for the Başçatak prospect. The age range of granite-related deposits forms two sub-groups:105–77 Ma and 61–50 Ma corresponding to the Upper Cretaceous and Paleocene transition. These data indicate that that the galenas were formed in two different stages in these mineralizations. Stratiform mineralization in the Başçatak prospect likely formed either through exhalative sedimentary processes by hydrothermal fluids or through chemical sedimentary processes under reductive conditions in a marine environment during metamorphism. O-1 appears to have been formed by hydrothermal fluids developed during granitic magmatism. A plausible formation process for O-2 involves the leaching of sulfur, lead and other metals from Başçatak type enrichments in metamorphics, with transportation and deposition within the epidotized calc-schist and marbles outside the granitoid contacts. The uplift of granitic intrusions prepared the channels and depositional environment for O-2 and caused heating of the hydrothermal fluids during this mineralization period.

Age, composition and paleomagnetism of dolerite-gabbro dolerite intrusions of the Anabar massif western slope: on the issue of the Vendian magmatism isolation in the region

According to the Anabar massif western slope geological survey in the Kotuy River middle reaches, the Kotuy intrusive complex was identified. It represented by dolerite-gabbrodolerite sills and dikes of Vendian age (556 ± 28 Ma). A number of sills are characterized by 30–80 m thickness, and dikes often have a length of the top tens km. The complex distribution area is the first hundreds of km2. At the same time, the geodynamic reasons for the formation extensive intrusive bodies in the north of Siberia in the Vendian are not clear. We present new geochronological, geochemical and paleomagnetic data indicating that at least part of the Kotuy magmatic complex intrusions in the middle reaches of the Kotuy River should be attributed to the ~1500 Ma Kengede magmatic complex (Kuonamka large magmatic province). In this light, the question arises about the correctness of the allocation of the stage of intrusive magmatism of the Vendian age on the western slope of the Anabar massif.

Kureika–Tunguska Composite Tectono-Sedimentary Element, northern East Siberia

The Kureika–Tunguska Composite Tectono-Sedimentary Element (KT CTSE) is located in East Siberia. Geologically, it is confined to the homonymic basin in the northwestern part of the Siberian Craton. The basement of the basin is composed of Archean–Early Proterozoic metamorphic rocks. The sedimentary cover is composed of Mesoproterozoic, Neoproterosoic and Early Paleozoic predominantly carbonate rocks capped with a succession of Pennsylvanian–Permian coal-bearing sediments overlain by thick section of Early Triassic tuffs and lavas. The entire sedimentary cover, especially its upper part, is saturated with mafic intrusive bodies. The maximum depth to the top basement can exceed 10 km. The KT CTSE is characterized by a very low degree of exploration. The rather scarce prospecting work carried out on oil and gas in the CTSE has not yet yielded positive results. However, indirect data such as, for example, numerous bitumen fields and evidence of the source rocks are promising for potential discoveries including large hydrocarbon accumulations.

Complex structure of the center Oktyabr’sky deposit, Norilsk district, Russia

The PGE-Cu-Ni Oktyabr’sky deposit, related to the Kharaelakh intrusion, contains the largest sulfide ore bodies in the world. Various models have been proposed to explain its formation based on the mineralogical and textural characteristics of the sulfide ores. However, the underlying structure of the intrusion, critical to understanding the deposit’s formation, has not been well studied until now. For the first time a 3D model of the center deposit with C-3 and C-4 orebodies representing its main part has been created. The model reveals that the intrusion in this area is a thin plate, rather than a tubular or honolithic body, as previously assumed. This morphology does not support the idea of ore formation by in situ reaction between primary magma and host rocks. Instead, sulfides were transported by magma from a deeper zone in the chamber. Within this area, two pulses of magma were identified, forming the Northern and Southern intrusive branches. They are similar in inner structure; however, some differences exist. The rocks of these intrusions are identical in terms of their major components but differ in metals (Cu/Ni ratios, Co, Zn, and V contents), which is particularly reflected in the composition of the chalcopyrite group of minerals. The picritic gabbro-dolerites presented in both intrusive bodies crystallized under similar conditions, namely, T and fO2, with an accuracy of the applied methods (±15 °C and ± 0.4 lgfO2, respectively) from two portions of magma that differ from those of the taxitic gabbro-dolerites. Therefore, the Oktyabr’sky deposit has a more complex structure in its central part than has been previously reported. Considering earlier published data from the western and eastern parts, it can be concluded that the Karaelakh intrusion consists of several intrusive bodies rather than a single large massif that should be consider in future models.

Every intrusion has its time: New zircon U-Pb ages from the Greater Antilles Arc in the Cordillera Central, Dominican Republic

The Cordillera Central on the island of Hispaniola comprises a section through the crust of the Late Cretaceous phase of the Greater Antilles Arc. The gabbroic-tonalitic batholiths of the Cordillera Central are widely considered to represent the temporal main axis of this island arc. Although they have been studied extensively, the timing of batholith emplacement is not well constrained. We present new LA-ICP-MS U-Pb zircon ages and whole-rock geochemical data from diorites, tonalites, and granites of the El Río, El Bao, Jumunuco, and Loma de Cabrera batholiths, and from tonalite boulders deposited in the Eocene-Oligocene Velázquitos Formation. The sample ages range from 97 to 80 Ma with small differences between the intrusive bodies. Samples from the El Río, Jumunuco, and Loma de Cabrera batholiths cover most of the above age range, while the rocks of the El Bao pluton yield a well-defined maximum around 87 Ma. In the El Río batholith, U-Pb ages are in good agreement with the exposed contact relationships. Based on their composition and existing geochronological data, we divide the intrusive history of the Cordillera Central into four stages reflecting different magma compositions: ultramafic to dioritic magmatism lasted from 105 to 87 Ma, tonalite units formed between 96 and 84 Ma, felsic tonalites and granites intruded from 87 to 80 Ma overlapping with a younger phase of dioritic magmatism between 84 and 78 Ma.The geochemical signatures of the felsic tonalites of the Jumunuco batholith and the granites of the El Río batholith are similar to the rhyolitic and dacitic island-arc volcanics from the Restauración Formation of the Tireo Group, thus confirming the relationship between the volcanic and plutonic units of the Greater Antilles Arc. Based on petrographical, geochemical, and geochronological data of the tonalite samples from the Velázquitos Formation, we interpret these boulders as being eroded from the Jumunuco batholith or the related Buena Vista pluton.

Deformation under a Young Volcanic Covered Area in Southern Garut, Indonesia: Insight from 3D Gravity Modelling

Destructive earthquakes are frequently related to inland active faults. In recent years, a significant number of shallow earthquakes with low magnitude have occurred in southern Garut, West Java, Indonesia. Two earthquakes, with magnitudes of M4.2 and M3.9 in 2016 and 2017, respectively, have caused significant damage and were interpreted as indications of an active fault. We used publicly available gravity data to infer the subsurface structure that may be related to recent seismic activity. We used spectral analysis and filtering techniques for the regional-residual anomaly separation and anomaly enhancement to show the basin structure in the study area. 3D gravity inversion modelling was performed to obtain the subsurface density distribution. The result indicates the sedimentary layers with a density of 2.4 to 2.5 gr/cm3 with an underlying basement with a density of 2.65 gr/cm3. An intra-basin basement high with an NE-SW trend divides the basin into two sub-basins. This local basement high can be associated with a magmatic intrusion body and a series of young volcanic bodies located at the northeastern end of the basin. Our results emphasize a possible strong interaction between the tectonic and magmatic activities in this region.

Oligocene magmato-tectonic events influential in the development of Pb-Zn, Ag, and Au mineralization at the Plomosas deposit, southwestern Sierra Madre Occidental, Mexico

ABSTRACT The Plomosas deposit is the product of a sequence of overlapping events of Pb–Zn, Ag, and Au low sulfidation mineralization that occurred in Mexico’s southwestern Sierra Madre Occidental (SMO). Field observations, detailed petrography, and U–Pb age dating of the entire stratigraphic sequence were used to characterize the magmatic evolution of the district and to obtain new insights into the evolution of the SMO. The stratigraphy at Plomosas is distinct from other areas to the north as it lacks Jurassic marine units, Cretaceous continental volcanic successions as well as Cretaceous and Palaeocene batholiths. The local basement is composed of undeformed Late Jurassic volcaniclastic units and coeval felsic intrusions. Early to late Oligocene silicic ignimbrites, intermediate lava flows, and occasional basaltic flows unconformably overlie the Jurassic basement. Several Oligocene intermediate to felsic porphyry bodies and rhyolitic domes crosscut the stratigraphy. The upper volcanic sequence is separated into two packages by an angular unconformity. Mineralization produced an early Pb–Zn-mineralized hydrothermal fault breccia, followed by Cu–Ag veins and late Au veins. The Pb–Zn mineralized breccia is hosted by ~30 Ma Oligocene volcanic units that form the basal sequence. The Cu–Ag and Au-rich veins overlap and crosscut the early hydrothermal features and cut the late Oligocene volcanic cover that unconformably overlie the basal sequence. Our results highlight the importance of episodes of Oligocene magmatism to the genesis of mineralization in the southwestern SMO specifically through a genetic link between Pb–Zn veins and intermediate Oligocene intrusive bodies, and of Ag and Au veins with late Oligocene volcanism.