This study aims to assess the transferability of unsupervised clustering with subsequent data-driven pegmatite prospectivity assignment to the under-explored south Leinster region, Ireland, where consistent genetic or targeting models for spodumene-bearing pegmatites are limited by very poor (< 1 %) outcrop. We apply self-organizing maps to simple, reproducible, and machine-readable features derived from airborne magnetic and radiometric data that capture lithological variability and tectonic stress pattern, deliberately excluding data sets potentially affected by displacement, anthropogenic activity or glacial overprint. The methodology segments the survey area by unsupervised clustering without using known pegmatite occurrences as training input. Probabilistic prospectivity maps are generated by aggregating multiple clustering realizations with known pegmatite occurrences. The results show that the approach reliably separates pegmatite-bearing from pegmatite-free boreholes and delineates a focused set of prospective zones, mainly along the eastern margin of the Leinster Granite, within the East Carlow Deformation Zone and along other major faults. Treating barren pegmatites separately further improves discrimination of targets. We conclude that airborne magnetic and radiometric data contain exploitable information on pegmatite emplacement, as they capture lithological variability and structural patterns in the near-surface ground, and that our approach provides a robust framework for early-stage exploration in data-poor regions.

This contribution is a new multimethod toolset to explore for buried, small-scale (0.01-5 million m3) rare metal and high-purity quartz pegmatites, which was developed as part of the four-and-a-half-year European Union H2020 GREENPEG project. It is underpinned by a complementary suite of existing, revised, and new methodologies, the use of three GREENPEG-developed geophysical exploration devices (EASA-certified, helicoptercompatible nose stinger magnetometer, piezoelectric seismograph, and drone-borne hyperspectral system), and two new databases (spectral library and petrophysical database for pegmatite ores). The toolset is based on the latest understanding of how pegmatites form and become enriched in ore minerals. In this regard, the theoretical component of the toolset resembles that of a comprehensive review article. The toolset has been tested in four active pegmatite exploration areas in a representative range of European surface environments-from coastal Arctic to temperate forest, alpine, and Mediterranean settings. Individual tools or tool combinations can be used to vector toward buried pegmatite-related mineralization, such as for Li, high-purity quartz for silica and metallic Si, ceramic feldspar, rare earth elements, Ta, Be, and Cs, to maximize the success of subsequent more costly exploration such as drilling in ways that optimize environmental, social, and governance outcomes. The tools are optimized for the small size, variable surface environment, depth, geologic setting, mineralogy, chemistry, and often highly variable physicochemical properties of pegmatite ore deposits. They can be used at province, district, and/or prospect scale. This guide is for those who have exploration knowledge and/or experience but who may be new or need updating in the state of the art of pegmatite exploration.

We compute probabilistic Niobium-Yttrium-Fluorine (NYF) pegmatite prospectivity maps in the Tysfjord region in Northern Norway. NYF pegmatites are generally enriched in rare earth minerals and represent residual melts derived from granitic plutons or melts formed by partial melting of metaigneous rocks. In Tysfjord, however, these pegmatites contain high-purity quartz, which is the major target commodity of exploration and mining. As the area is geologically underexplored, we employ a data analytics approach for the discovery of new deposits. We carefully lay out our knowledge base and how it impacts the working hypothesis and feature engineering. Self-organizing maps are employed as an unsupervised and random forest classification as a supervised data analytics algorithm to process and link features derived from airborne magnetic and radiometric maps with sparse pegmatite occurrences available in the form of outcrops and active and abandoned mines. The predictive power of our probabilistic pegmatite prospectivity maps is analysed by means of additional boreholes, which indicates the usefulness of our prospectivity maps for exploration targeting. We recommend employing unsupervised and supervised data analytics approaches in exploration targeting case studies where uncertainty about the predictive power of the available database cannot be ruled out before subjecting the database to data analytics.

Deciphering the history of active continental margins is of key importance for paleogeographic reconstructions, but the low preservation potential of such margins commonly hampers such attempts and may introduce unrecognized biases. Here, we present new sedimentological observations and detrital zircon U-Pb and Hf isotopic data from the Ediacaran-Cambrian Vestertana Group in Finnmark, Arctic Norway. The data are consistent with derivation from the Fennoscandian Shield and the appearance of an Ediacaran source at the Ediacaran-Cambrian transition. However, the new paleocurrent observations dispute that this influx is related to a change in paleocurrent direction from northerly to southerly. Instead, we argue for the possibility of an alternative source represented by the Kalak Nappe Complex, which we suggest may be a remnant of a Neoproterozoic accretionary margin outboard of western Baltica that was thrust onto Baltica during the Ediacaran rather than during the Silurian Caledonian Orogeny. Further work focusing on detrital minerals other than zircon may provide a more comprehensive understanding of the character of these potential sources. Comparisons with detrital zircon data from Ediacaran-Cambrian sedimentary rocks around the North Atlantic show that both Baltica and Siberia are characterized by large Neoproterozoic populations, while such ages are all but absent from Laurentia. The apparent link between Baltica and Siberia during the Ediacaran-Cambrian is consistent with fossil data and suggests that the two continents were separated from Laurentia by this time.

Trøndelag county has been recently the focus of a new mineral exploration wave given its well-known base metal mineralization potential associated with the occurrence of volcanogenic Cu-Zn (±Co±Ag±Au) massive sulfide deposits (VMS). This study evaluates a regional low-density soil sampling survey by implementing principal component analysis (PCA), and compositional balance analysis (CoBA) to target prospective areas for base metal mineralization. Principal component analysis indicates a dominant base metal mineralization signature characterized by a correlation between As and Cu-Cr-Co-Ni, which is consistent with the occurrences of mafic metavolcanic and associated low K-Ca metasedimentary rocks. However, several other Cu-Zn occurrences hosted in K- and/or Ca-rich (meta-)sedimentary (e.g., Røros districts) and felsic (meta-)igneous lithologies have been overlooked by this approach. Data- and knowledge-driven balances (i.e., isometric log-ratios) were then constructed aiming to enhance these “weaker” Cu-Zn(±Co) mineralization fingerprints. Most of the data-driven balances (dcobals) are shown to be very noisy, and less useful for base metal geochemical anomaly mapping compared to their more coherent knowledge-driven counterparts (kcobals). However, the kcobals (e.g., for Cu, Zn and Co) highlight relatively large anomalous areas, which makes them less practical if used individually as exploration vectors. To further define zones of economic interest, common anomalous areas (defined as kcobal > 75th percentile) have been filtered out from selected kcobal pairs. This has resulted in the identification of several prospective areas that correspond with 15% to 20% of the Trøndelag county.This study not only explores the combined use of CoBA and PCA for detecting base metal anomalies, but also elaborates on some factors that can affect the interpretation and performance of multivariate approaches (e.g., mineralization/alteration extension versus survey resolution, geological framework, and deposit type). The visualization and implementation of CoBA presented in this paper aim to improve geoscientists’ understanding of the reach and limitations of using isometric log-ratios for mineral exploration studies.

Late Ediacaran opening of the Iapetus Ocean is typically considered to reflect separation of Baltica and Laurentia during final breakup of the Rodinia supercontinent, with subsequent closure during the Caledonian Orogeny. However, evidence of the pre‐opening juxtaposition of Baltica and Laurentia is limited to purportedly similar apparent polar wander paths and correlation of Rodinia‐forming orogenic events. We show that a range of existing data do not unequivocally support correlation of these orogens, and that geologic and palaeomagnetic data instead favour separation of Baltica and Laurentia as early as 1.1–1.2 Ga. Furthermore, new detrital zircon U–Pb age and Ar–Ar thermochronological data from Norway point towards an active western Baltican margin throughout most of the Neoproterozoic and early Palaeozoic. These findings are inconsistent with the majority of palaeogeographic reconstructions that place Baltica near the core of the Rodinia supercontinent.

The nappe stack in the Røssvatnet–Hattfjelldal region in the Central Norwegian Caledonides consists of seven nappes formed at the boundary between tectonostratigraphically upper and uppermost Caledonian levels. The rocks of all nappes share a polyphase tectonometamorphic evolution that is younger than the 491 ± 10 Ma depositional (volcanic) age of parts of the succession. Early stages of deformation characterized by centimetre- to kilometre-scale folding and intense shearing accompanied by greenschist to amphibolite facies peak metamorphism are correlated with the Early Ordovician Taconian accretionary orogeny along the Laurentian margin. The Taconian structures are cut by the Krutfjellet gabbro and diorite, which yield U–Pb zircon ages of 446 ± 5 and 444 ± 4 Ma, respectively. Large-scale nappe stacking and folding post-dating the emplacement of the gabbro is related to the collision of Laurentia with Baltica (Scandian orogeny) and was followed by late- to post-orogenic extension. The revised tectonostratigraphy assigns the structurally higher nappes to the Uppermost Allochthon, whereas the lower nappes are correlated with the Middle Köli Nappe Complex (Upper Allochthon). The boundary between these nappes is marked by an imbricate zone. Taconian deformation was probably much more penetrative and widespread than hitherto thought and therefore parts of the nappe stack were probably assembled before Scandian collision. Supplementary material: Electronic Supplement 1: U–Pb zircon data and Electronic Supplement 2: Methods (laser ablation inductively coupled plasma mass spectrometry U–Pb zircon geochronology) are available at https://doi.org/10.6084/m9.figshare.c.5357255

Abstract The Scandinavian Caledonides consist of disparate nappes of Baltican and exotic heritage, thrust southeastwards onto Baltica during the Mid-Silurian Scandian continent–continent collision, with structurally higher nappes inferred to have originated at increasingly distal positions to Baltica. New U–Pb zircon geochronological and whole-rock geochemical and Sm–Nd isotopic data from the Rödingsfjället Nappe Complex reveal 623 Ma high-grade metamorphism followed by continental rifting and emplacement of the Umbukta gabbro at 578 Ma, followed by intermittent magmatic activity at 541, 510, 501, 484 and 465 Ma. Geochemical data from the 501 Ma Mofjellet Group is indicative of arc magmatism at this time. Syntectonic pegmatites document pre-Scandian thrusting at 515 and 475 Ma, and Scandian thrusting at 429 Ma. These results document a tectonic history that is compatible with correlation with peri-Laurentian and/or peri-Gondwanan terranes. The data allow correlation with nappes at higher and lower tectonostratigraphic levels, including at least parts of the Helgeland, Kalak and Seve nappe complexes, implying that they too may be exotic to Baltica. Neoproterozoic fragmentation of the hypothesized Rodinia supercontinent probably resulted in numerous coeval, active margins, producing a variety of peri-continental terranes that can only be distinguished through further combined geological, palaeomagnetic and palaeontological investigations.

The Sveconorwegian orogeny encompasses magmatic, metamorphic and deformational events between ca. 1140 and 920 Ma at the southwestern margin of Fennoscandia. In recent years, the tectonic setting of this nearly 200 Myr-long evolution has been debated, with some workers arguing for collision with an unknown continent off the present-day southwest coast of Norway, and others advocating accretionary processes inboard of an active margin. Recently, it has been suggested that orogeny may have been gravity-driven by delamination and foundering of heavy subcontinental lithospheric mantle in an intraplate setting, in some ways similar to proposed sagduction processes in the Archaean. Resolving the tectonic setting of the Sveconorwegian orogen has implications for correlation with other orogens and Rodinia supercontinent reconstructions and for assessments of the evolution of plate tectonics on Earth, from the Archaean to the present. Here, we present new mapping and geochronological data from the Bamble and Telemark lithotectonic units in the central and western Sveconorwegian orogen - the former representing a critical region separating western parts of the orogen that underwent long-lived high- to ultrahigh-temperature metamorphism and magmatism from parts closer to the orogenic foreland that underwent episodic high-pressure events. The data show that the units constituting the Sveconorwegian orogen most likely formed at the southwestern margin of Fennoscandia between ca. 1800 and 1480 Ma, followed by fragmentation during widespread extension between ca. 1340 and 1100 Ma marked by bimodal magmatism and sedimentation. A summary of Sveconorwegian magmatic, metamorphic and depositional events in the different units shows disparate histories prior to their assembly with adjacent units. The most likely interpretation of this record seems to be that episodic, Sveconorwegian metamorphic and deformational events in the central and eastern parts of the orogen represent accretion and assembly of these units. This process most likely took place behind an active margin to the southwest that sustained mafic underplating in the proximal back-arc, resulting in high- to ultrahigh-temperature metamorphism in the western parts. In this interpretation, all features of the Sveconorwegian orogen are readily explained by modern-style plate tectonic processes and hypotheses involving some form of vertical, intraplate tectonics are not supported.

One of several irregular, plagioclase-phyric felsic veins in the Lillevik ophiolite fragment (Gratangseidet Igneous Complex) in Narvik, northern Norway, yielded a U–Pb zircon age of 494 ± 5 Ma. The veins cut deformed, compositionally layered, light REE-depleted gabbros that arguably constituted part of the now-dismembered ophiolite stratigraphy. The felsic veins were themselves deformed, probably during Silurian Scandian deformation, but the cross-cutting relationships suggest that they post-date initial deformation of the ophiolitic rocks. The felsic veins are strongly depleted in heavy REE and have moderately juvenile Lu–Hf zircon compositions, with εHf494 between 6.2 and 9.9. By analogy with felsic rocks in other Caledonian ophiolites and supported by cross-cutting relationships, the chemical and isotopic data can be interpreted to reflect formation by partial melting of basaltic rocks in the presence of residual garnet. In this case, the felsic veins probably post-date ophiolite formation and obduction onto a continental margin. We therefore interpret the age of 494 Ma to represent the minimum age of formation of the Lillevik ophiolite fragment. Previously published age, isotopic and chemical data from the region document an at least 20 Myr-long complex magmatic evolution following ophiolite obduction. The new data show that Late Cambrian to Early Ordovician ophiolite fragments extend along most of the length of the Scandinavian Caledonides. The tectonic significance of a previously published age of 474 Ma from the Gratangseidet Igneous Complex and 481 to 469 Ma ages from a tonalite sheet in the nearby Lyngen ophiolite, both interpreted to reflect ophiolite formation, needs to be tested by obtaining whole-rock geochemical data from these units. ablation cathodoluminescence LA–ICP–MS using ablation.

The Mumbwa mineralized district is located approximately 200 km west of Lusaka, at the north-eastern margin of the Pan-African granitic Hook batholith. Polymetallic sulphide occurrences in the area have been known for hundreds of years, but more recent geophysical and geochemical investigations led to the discovery of a copper rich hydrothermal system, mostly associated with late-stage syenite intrusions of the Hook batholith. The extent of the hydrothermal system is not known, but to date two main centres have been identified, the Sugar Loaf and Mutoya. Sulphide mineralization occurs along regional-scale lineaments, following a 25 km-long NNW-trending corridor. Mineralized host rocks are characterized by brecciation, often pervasively replaced by magnetite-hematite, and by strong metasomatism with multiple - and often superimposed - alteration cycles, from potassic, to carbonate, sericite-chlorite and amphibole-apatite-carbonate. Sulphur isotopes suggest that a mixture of magmatic and sedimentary-derived evaporitic fluids were critical in providing sulphur and metals. Late syenitic intrusions triggered the relevant hydrothermal circulation and favoured the mineralization processes. Diagrams plotting key element geochemistry and alteration indexes highlight vectors to alteration and mineralization and suggest that the sulphides preferably concentrated in rocks affected by hydrothermal iron oxides in association with sericite-chlorite alteration. At the Kitumba prospect (in the Sugar Loaf mineralized centre), granitic to syenitic bodies host a hypogene copper mineralization (mostly chalcopyrite), that was subsequently overprinted by pervasive and deep super gene mineralization (malachite, chalcocite, chalcosiderite, cuprite, digenite, chrysocolla, bornite, native copper). Supergene mineralization has been identified in boreholes to depths exceeding 700 m. Reserves at Kitumba are estimated at 27.9 Mt with an average grade of 2.2% copper at a 1.0% copper cut-off grade. Gold is present, although generally at low grades. In the Mutoya centre, metasedimentary rocks alternate with felsic intrusions. Two prospects have been identified, characterized by large areas of magnetite-hematite breccias hosting sulphide mineralization with predominantly pyrite and minor chalcopyrite. An affiliation to the iron oxide copper gold (IOCG) category is discussed. Many, but not all of the distinctive IOCG features, are present in the studied area.

The Aswa Shear Zone (ASZ) is a major NW SE trending structure of over 1000 km length in East Africa. In Uganda, the ASZ is a steeply NE-dipping, up to 11 km wide mylonitic shear zone that shows multiple stage brittle reactivation. On outcrop -scale, the fabric in the ASZ is characterized by a well-developed NW SE striking and subvertical or steeply NE or SW dipping mylonitic foliation and a subhorizontal to moderately NW- or SE-plunging stretching lineation. Sinistral kinematics and fabric are very consistent along strike. The strain is heterogeneously distributed and partitioned into lens-shaped lower strain zones dominated by folding and characterized by pure shear, which are surrounded by high strain zones, some of them thick ultramylonites, with intense simple shear combined with flattening and strong transposition of pre-existing fabrics. Ductile shearing occurred during bulk E-W shortening, commenced at amphibolite facies conditions and continued with similar kinematics at greenschist and even lower grade conditions. A number of (sub-)parallel shear zones occur to the NE and SW of the main zone at a distance of up to 20-45 km. They show similar fabrics and kinematics and are thus related to activity along ASZ reflecting strain partitioning into simple shear and pure shear domains on a regional scale.Samples of mylonitic gneisses from the shear zone have been analyzed with U Pb LA-MC-ICPMS and show Neoarchaean crystallisation ages between 2.66 and 2.61 Ga. Timing of ductile sinistral shearing is poorly constrained by lower intercept ages of 686 62 and 640 44 Ma. The fabric and structural relationship of the ca. 660 Ma Adjumani Granite exposed in the northern segment of ASZ suggest that the age of shear activity can be further limited to ca. 685 and 655 Ma.The Aswa Shear Zone is interpreted as an intra-cratonic, crustal -scale structure close to the northeastern margin of the Congo Craton, possibly inherited from previous continental extension. Early Aswa Shear Zone activation is linked to underthrusting of the Congo Craton and coeval high-grade metamorphism and intense deformation in the orogen interior. During E W convergence between ca. 690 and 650 Ma, the NE -dipping ASZ was activated as an oblique ramp leading to deflection of the transport direction and concentration of non -coaxial strain and sinistral shear along the shear zone system. During progressive convergence, between ca. 645 and 620 Ma, sinistral shearing along ASZ changed to ductile brittle deformation mechanisms, while thrusting took place in Pan-African belts in eastern and western Uganda. Late-orogenic brittle sinistral reactivation of the ASZ can be regarded as the result of continent collision and closure of the Mozambique ocean further to the east, that potentially caused lateral escape manifested in NW SE striking sinistral shear zones in Kenya and the southern Arabina-Nubian Shield between 620 and 570 Ma. (C) 2016 Elsevier Ltd. All rights reserved.

The Pan-African Orogen formed by convergence of numerous continental blocks during the Neoproterozoic to early Cambrian. This convergence eventually led to amalgamation of Gondwana, a supercontinent crosscut by a network of highly oblique linear orogenic belts that locally intersect each other, as in NW Namibia, where the NNW trending Kaoko Belt joins the NE trending Damara Belt. The northern Damara Belt has preserved well three regional Pan-African tectonic events due to the dominance of weak Neoproterozoic marine sediments (Damara Supergroup) that have been affected by low-grade metamorphism. A newly discovered early N-S horizontal contraction, dated by Ar-40/Ar-39 at similar to 590Ma, is tentatively linked to convergence between the Congo and Kalahari cratons. This was superseded by collision between the Congo and Rio de la Plata cratons between 580 and 530Ma that thickened and exhumed the orogenic crust of the Kaoko Belt and produce upper crustal N-S oriented folds of earlier fold trains and associated axial planar schistosities in the northern Damara Belt. A switch from E-W to NW-SE horizontal shortening occurred at similar to 530Ma as a result of collision with the Kalahari Craton, triggering extensive syn-orogenic magmatism in the entire Damara Belt. During this last event, southward indentation and underthrusting of the Congo Craton promontory below the Neoproterozoic cover sequences produced a deformation front in the northern Damara Belt. Our results show that highly oblique convergent processes competed over a period of similar to 120Ma to build Gondwana in Namibia during the late Neoproterozoic to early Cambrian.

much of the subcontinent in the World Stress Map database. As a consequence, it is generally difficult to determine the reactivation potential of known faults, permissible only if they line up close to the direction of maximum horizontal compressive stress (σH). To obtain this datum, or even better the orientation of the principal compressive stresses (σ1>σ2>σ3), we installed 3 compact Trillium stations across the Grootvloer seismic cluster (Bushmanland, Northern Cape) whose data will be integrated with those from the national network to obtain focal mechanism solutions. These neotectonic stress tensors are then combined with σH parameters obtained from caliper logs of off-shore wells and from the geometry of joints, faults and sheared fractures in palaeosols (Bushmanland), soils and calcrete (NW Free State) and aeolianites (southern Cape). We also include underground rock engineering phenomenological observations and measurements (Witbank coal field), and data in the public domain. Our data consistently indicate a NNW-SSE oriented σH (Wegener Stress Anomaly or WSA) prevailing across most of central, southern and western South Africa/Namibia not further than southern Angola. We also found that the WSA is the last of at least 7 successive tectonic regimes to leave their brittle imprints along the SE Atlantic seaboard since the break-up of W Gondwana. In conclusion, the state of stress in South Africa holds many uncertainties, including the strike-slip to transpressional character of the WSA, its rapidly changing strength and stain rate and the influence of the E African Rift System.

The late Mesoproterozoic to Neoproterozoic Kalahari Copperbelt (KCB) in Namibia and Botswana is widely covered by Kalahari sand, which precludes direct correlations between known stratabound sediment-hosted Cu-Ag districts. We use a combination of review of literature data, and newly processed and interpreted high-resolution aeromagnetic maps in both countries to provide a new correlative cross-border interpretation. Lithostratigraphic control on the aeromagnetic response allows detailed indirect mapping of the Kalahari Copperbelt lithotectonic domains below the sand cover. This enabled us to redefine the width and lateral extent of the KCB as two continuous magnetic domains (the Rehoboth and Ghanzi-Chobe domains) extending from central Namibia to northern Botswana, and helped in resolving problems of stratigraphic correlations across the international border.The Rehoboth magnetic domain, in the western part of the KCB in Namibia, records continental arc magmatism at similar to 1200 Ma during orogenic events along the northwestern edge of the Kalahari Craton. This was followed at 1110-1090 Ma by widespread magmafism, identified within the entire KCB, and related to the 1112-1106 Ma Umkondo Large Igneous Province. The basal parts of the Tsumis Group in Namibia and Ghanzi Group in Botswana were deposited in shallow-water environments after a period of erosion and peneplanation. Subsequently, and prior to the Sturtian glaciation, the host-rocks of the Cu-Ag deposits formed by the deposition of chemically reduced shales and siltstones that formed in deeper water and overlie chemically oxidised shallow-water sandstones. This regional interface, which is both a permeability barrier and redox boundary, played a critical role in the formation of the stratabound sediment-hosted Cu-Ag deposits of the Kalahari Copperbelt, and the interface, with its strong magnetic contrast, can be followed through the entire Ghanzi-Chobe magnetic domain of the copperbelt The whole KCB was affected by the Damara Orogeny during early Cambrian times, which resulted in the formation of a NE-SW trending similar to 250 km-wide fold-and-thrust belt. (C) 2015 Elsevier B.V. All rights reserved.

The Matala Dome (MD), an ENE-trending structure located at the junction between the Pan-African Lufilian and Zambezi belts, is cored by a Gneiss-Schist Unit with uncertain age overlain by a metasedimentary section (Quartzite-Schist Unit, Marble Unit and Carbonate-Siliciclastic Unit) of the Neoproterozoic to Cambrian Katanga Supergroup. The top of the Katangan stratigraphy is represented by synorogenic sedimentary rocks—Upper Siliciclastic Unit. An early event D1 resulted in the development of shallow-dipping metamorphic foliation S1 and pre- to syntectonic growth of garnet and kyanite in the schists of the Quartzite-Schist Unit. Pseudosections and garnet isopleth modelling on schist from this unit defined the peak metamorphism at P = 7.5–9.3 kbar and T = 620–700 °C. U–Pb detrital zircon dating revealed ca. 2.7 Ga source and a high-grade metamorphism during Pan-African times. The S1 foliation was affected by upright folding F2 with ENE-trending axes and associated subvertical crenulation fabric S2 development. The syn-D2 retrogression in the schists is marked by post-S1 staurolite crystallisation and further by chloritisation followed by sericitisation. The D2 event is interpreted to have exhumed the orogenic middle crust and to be responsible for the domal structure of the MD. 40Ar/39Ar dating of muscovite at 529.3 ± 5.6 to 526.3 ± 6.2 is interpreted to date the exhumation event. D2 is correlated with regional N–S shortening event at ca. 530–520 Ma. Based on the lithology, structural record, and time and facies of the metamorphism, a correlation between the MD and the northern part of the Zambezi Belt is suggested.

The tholeiitic to calc-alkaline Goas Complex represents the earliest magmatic activity of the inland branch of the Damara Orogen, and reflects the Pan-African convergence between the Congo and Kalahari Cratons. New results from laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb geochronology coupled with single-zircon Lu–Hf isotopic data constrain the age of emplacement and allow the identification of a crustal contribution to the magma sources. No temporal gap is registered between the first tholeiitic intrusion at ca. 575Ma and the main diorite to granite episodes. Invariably sub-chondritic εHft values (−3.8 to −34.4) attest to a significant crustal residence time with long-term reworking of multiple and mixed crustal components. No significant juvenile magma was involved in the magmatogenesis. Hf model ages coupled with an exhaustive dataset of U–Pb geochronological data suggest that the crustal components which fed the Goas sources might have formed during specific orogenic events with a major contribution of material derived from the central-western African Paleoproterozoic Eburnean Orogen. Geochemistry, U–Pb geochronology and Hf isotope systematics however, do not unequivocally clarify the long debate regarding whether or not the Pan-African orogenic cycle included ocean closure and subduction, as the involvement of crustal melting processes during the early stage of the Damaran event seems to have played a major role.

The Pan-African Hook Batholith formed during the assembly of the Gondwana supercontinent as a result of syn-collisional stage interaction between the Congo and Kalahari Cratons. The bimodal magmatism (mafic to predominantly felsic) is characterized by both an alkali-calcic and an alkalic suite, with typical A-type, metaluminous, high Fe/Mg and K/Na geochemical signature. Occasionally, sodic granitoids have been documented. Compositions were driven to more differentiated products by fractional crystallization, while Sr–Nd isotopes exclude crustal assimilation during crystallization. Recent new U–Pb age data constrain most of the felsic magmatism between 550 and 540Ma. Scattered outcrops of gabbroic rocks, both tholeiitic and alkaline, testify to periodic input of mantle material, and, in some cases, to interaction with metasomatizing fluids. Crystallization ages on mafic rocks span from 570 to 520Ma, thus indicating that they were contemporaneous with the major granitic intrusion, which was the result of a number of successive felsic batches, eventually forming a coalescing batholith. Highly radiogenic Pb isotopic values attest to the radiogenic character of the rocks. Such an anomalous signature was acquired during, or soon after, magma emplacement, perhaps as result of metasomatizing fluids. Enrichment in Th–U of large portions of the crust along this part of the margin of the Congo Craton is suggested. Geochemical and isotopic evidence support the interaction between mantle components and portions of the deep crust at pressure of < 10kbar, while decompression melting of rising asthenospheric mantle ponding at the base of the crust heated, and ultimately melted, crustal material. An additional and crucial contribution to the crustal melting was likely provided by internal radiogenic heat production of the thickened crust, and is in agreement with the high radioactivity of the pluton. A tectono-thermal model, implying crustal accretion accompanied by slab retreat and lithospheric mantle thinning, is proposed to reconcile coeval orogenic contraction in the crust and A-type magmatism. Low-pressure mineral phases in metasedimentary wall rocks along the eastern margin of the pluton indicate that the magma was emplaced at shallow crustal depths. This study further supports the idea that A-type granites, commonly considered to be restricted to anorogenic or extension-related environments, can also occur in compressional regimes.