Sedimentary provenance studies reveal stratigraphic relationships obscured by orogeny that can be critical for testing tectonic models and for unravelling the geodynamic evolution of ancient mountain belts. Multiproxy analyses are applied in this study for reconstructing paleo-tectonic events in the central portion of the Neoproterozoic Brasilia orogen in Brazil. The Passos Nappe incorporates metasedimentary rocks and minor metabasic rocks that represent a subducted portion of a Tonian passive margin. Nine lithological units (A to I) comprising metapsammites and metapelites show a common deformational history and inverted metamorphic gradient from greenschist to granulite facies. The paleoenvironments and deposition period of these metasedimentary rocks are unknown, even though they are key to understanding the evolution of the São Francisco continental margin. This study presents new data including U-Pb ages of detrital zircon, whole-rock major and trace element and Sm-Nd-Sr isotope compositions for the Passos Nappe units. The results indicate that the Passos Nappe may be divided into three tectonic-stratigraphic levels (TS1 to TS3) characterised by abrupt shifts in the sedimentary provenance pattern. In TS1, the main zircon population yields ages between c. 2.15 and 2.05 Ga with a minor c. 2.6 Ga component, while TDM varies between 2.69 and 2.14 Ga. Biotite-rich rocks in TS1 yield a low chemical index of alteration (49.4 - 61.9 mol%), high Lan/Ybn ratios (21.2 - 35.1), and Sr/Y ratios (27.2 - 85.6), indicating derivation from Paleoproterozoic basement (magmatic arc) sources. TS2 yields detrital zircon with ages varying from c. 0.82 to 0.72 Ga, c. 1.53 to 0.93 Ga, and c. 2.29 to 1.64 Ga with a maximum depositional age of c. 0.79 Ga. The TDM varies between 1.21 and 2.44 Ga, and samples with a conspicuous mid-Tonian detrital zircon contribution also yield εNd790 Ma between -7.0 and +0.8. The comparatively juvenile character of the magmatism is supported by an orthogneiss sample with a crystallisation age of 795 ± 8 Ma and εNd790 Ma of +2.1. TS3 is characterised by detrital zircon between c. 1.06 to 0.65 Ga, c. 2.45 to 1.73 Ga, and c. 2.91 to 2.53 Ga, with a maximum depositional age of 654 ± 6 Ma. The εNd650Ma ranges from -7.5 to +0.5 and low Th/Sc ratio (0.33 to 0.66) indicate the input of a relatively juvenile Neoproterozoic source. These new results indicate that mantle-derived active magmatism and a shift in the provenance of source rocks accompanied the deposition of TS2 during the mid-Tonian continental rifting of the precursor block of the São Francisco paleocontinent. Moreover, TS3 is now recognized as a syn-collisional metasedimentary succession that is structurally in the basal portion of the Passos Nappe.

The Paleoproterozoic basement of the Central Terrane, exposed in the central segment of the Ara & ccedil;ua & iacute;-Ribeira Orogenic System (SE-Brazil), provides key constraints on crustal evolution and pre-Brasiliano paleogeography in the region. New zircon U-Pb ages, whole-rock geochemical and Nd-Sr isotopic data, and regional comparisons reveal that this basement shares a similar evolutionary history with Paleoproterozoic units in the southern sector of the Sao Francisco Paleocontinent. Hbl orthogneisses yield Rhyacian (c. 2.09 Ga) crystallization ages and geochemical features typical of TTG suites, including high Sr/Y ratios (342), strongly fractionated REE patterns, positive Eu anomalies (Eu/Eu* = 2.52) and juvenile signatures (epsilon Ndi = +5.8). These characteristics match those of coeval units related to continental magmatic arcs in the Mantiqueira and Juiz de Fora complexes and in the Mineiro Belt along the southern margin of the Sao Francisco Paleocontinent. A Statherian mafic pulse (c. 1.68 Ga), represented by an E-MORB orthoamphibolite (epsilon Ndi = +2.7), marks a crustal extension stage in the tectonic evolution of the Central Terrane basement. The data strongly support a model in which the Central Terrane represents a ribbon-type microcontinent derived from the Sao Francisco Paleocontinent. The detachment of this ribbon occurred at c. 1.00-0.95 Ga during the breakup of the Sao Francisco-Congo Paleocontinent and opening of the Adamastor Ocean. This ribbon microcontinent, together with other fragments, reconverged during the Ediacaran, forming the continental block that hosted the Inner Cordilleran magmatic arc during the final closure of the Adamastor Ocean. Thus, the Paleoproterozoic basement of the Central Terrane constitutes a key element for reconstructing the paleogeographic framework of Western Gondwana assembly.

Abstract Mafic-to-felsic magmatic suites commonly occur in convergent margins, providing a unique opportunity to reveal the geodynamic evolution and mantle–crust interactions during oceanic subduction. This study presents new zircon U–Pb geochronology, whole-rock geochemistry (major and trace elements, Sr-Nd-Pb isotopes), mineral chemistry, and zircon Hf–O isotope data from the Muztaga and Taer plutons in the West Kunlun Orogenic Belt (WKOB), northwest Tibetan Plateau. The Muztaga–Taer plutonic complex consists of mafic-intermediate rocks (including microgranular mafic enclaves [MMEs], mafic dikes, and gabbroic diorites) and granites. Zircon U–Pb dating reveals crystallization ages of ca. 233 Ma for the mafic dikes, ca. 226 Ma for the MMEs, ca. 223 Ma for the gabbroic diorites, and ca. 244–216 Ma for the granitoids. The mafic-to-intermediate rocks (SiO2 = 48.7–58.2 wt %; Cr = 19–474 ppm; Ni = 11–182 ppm) exhibit high large-ion lithophile elements (LILEs, e.g. Rb, Ba, and K) and low high-field-strength elements (HFSEs, e.g. Nb, Ta, P, and Ti), as well as high whole-rock (87Sr/86Sr)i ratios (0.7058 to 0.7071) and negative whole-rock εNd(t) values (−3.5 to −3.0), indicating derivation from an enriched lithospheric mantle source. Temporal variations in the in situ zircon Hf–O isotopic ratios suggest that the mantle source was modified by subducted sediment-derived melts over a protracted period of time. Estimates derived from mineral geobarometers and trace element modeling suggest generation by variable degrees partial melting of spinel- to garnet-facies mantle sources at different depths. The Muztaga and Taer granitoids display characteristics of I-type granites with elevated SiO2 (66.4–74.7 wt %), Na2O (2.96–4.44 wt %), and δ18Ozrn (6.28‰–7.51‰). Together with enriched (86Sr/87Sr)i (0.7070 to 0.7085), εNd(t) (−4.31 to −3.53) and εHf(t) (−5.27 to +1.51), these features indicate a likely derivation via remelting of an ancient crustal source. The temporally and spatially associated mantle-derived mafic-intermediate rocks and crust-derived granites collectively constitute a Triassic intrusive suite within the WKOB. To constrain the driving forces and evolutionary pathways of this magmatic system controlled by Paleo-Tethys subduction, we establish a comprehensive petrogenetic model as follows: (1) northward subduction of the Paleo-Tethys slab induced partial melting of the heterogeneous hydrous lithospheric mantle, generating primitive mafic magmas; (2) processes operating within magmatic recharge zones modified mantle-derived magmas through magma storage and recharge, producing diverse mafic-intermediate lithologies; and (3) mafic magma underplating provided thermal and aqueous fluxes for lower crustal melting and granite generation. Regional geochronological and geochemical data indicate that the Pamir-WKOB formed an active continental margin during the Triassic–Early Jurassic, driven by sustained northward Paleo-Tethys slab subduction. When considered together with regional metamorphic-sedimentary records, these data reveal a two-stage geodynamic evolution of the Paleo-Tethys oceanic subduction system as follows: (1) early Triassic flat–slab subduction promoted back-arc crustal thickening and the generation of granites and (2) the onset of slab roll-back at ca. 223 Ma triggered voluminous continental arc magmatism, accompanied by crustal thinning and extension, which ultimately led to the final closure of the Paleo-Tethys Ocean during the Late Triassic–Early Jurassic.

Cenozoic crustal thickening and surface uplift in Pamir, northwest Tibetan Plateau is controlled by India-Asia continental convergence and post-collisional subduction processes. However, the nature and evolution of post-collisional subducted lithosphere and the associated deep dynamic processes remain unclear. In this study, we report new geochemistry, mineral chemistry and geochronology for three plutons (Kuzigan, Karibasheng and Zankan) in eastern Central Pamir to constrain their petrogenesis and help understand the associated post-collisional geodynamic processes. LA-ICP-MS U-Pb zircon dating indicates that the Kuzigan and Karibasheng plutons were emplaced in the Late Miocene (ca. 11.2-10.7 Ma). Whole-rock compositions are characterized by high Ba (1890-7550 ppm) and Sr (1050-3570 ppm), as well as crust-like Sr-Nd-Pb-Hf-O isotopic compositions, thus with a marked affinity to high Ba-Sr granitoids. Mafic to intermediate syenites have moderate Mg-# values (up to 55), as well as Cr (up to 104 ppm) and Ni (up to 59 ppm) contents, indicative of a mantle source. They have negative epsilon(Nd)(t) (-9.22 to -8.87) and epsilon(Hf)(t) (-11.8 to -6.49), combined with high (Sr-87/Sr-86)(i) (0.7099-0.7109) and delta O-18(zrn) (+9.99 parts per thousand to +10.9 parts per thousand), as well as enrichment in large ion lithophile elements (LILEs, e.g. Ba, U, Th and K) and depletion in high field strength elements (HFSEs, e.g. Nb, Ta, P and Ti). These features suggest an origin from enriched lithospheric mantle, modified by subduction-related melts. Sr-Nd-Pb isotope modeling indicates contributions from both the Indian plate (similar to 20-30%) and the Asian plate (similar to 1-3%). Associated syenogranites exhibit a mineral assemblage and isotopic compositions similar to the syenites, as well as parallel trace-element patterns, indicating a common magma source. Their geochemical variability likely reflects fractional crystallization of clinopyroxene, biotite, rutile, feldspars and accessory phases (titanite, zircon, apatite and allanite). The Karibasheng monzogranites, by contrast, have uniformly high SiO2 (70.9-72.5 wt %) but lower MgO (0.36-0.48 wt %) compared to the syenitic rocks. Their low epsilon(Nd)(t) (-7.46 to -6.88) and epsilon(Hf)(t) (-11.9 to -5.80), along with high (Sr-87/Sr-86)(i) (0.7091-0.7092) and delta O-18(zrn) (+8.75 parts per thousand to +10.7 parts per thousand), point to derivation from the remelting of ancient metasedimentary rocks. Combining these data with regional geochronology and previous geophysical studies, we propose a west-to-east magmatic migration in the Central Pamir and a gradual delamination model to explain the origin of Miocene magmas. Blocked by the subducting Indian plate, continental crust foundered resulting in asthenosphere upwelling and subsequent melting of the lithosphere, producing high Ba-Sr syenites. Given the spatial-temporal distribution of Pamir magmatism and the associated regional geology, we suggest that the deep geodynamic evolution of the lithosphere was the primary driver of Late Cenozoic tectonic uplift in the Pamir. This study highlights the deep link between continental delamination, mantle processes and generation of Miocene magmas in Central Pamir and provides new insights into episodic uplift of Pamir.

The tectonic setting of Tonian orogenic events recorded in the present-day circum-North Atlantic region is uncertain. U-Pb zircon geochronology shows that the Yell Sound and Westings groups (Shetland) and metasedimentary rocks of the Naver Nappe (northern mainland Scotland) were deposited between c. 1050 and 960 Ma and intruded by mafic, intermediate and felsic igneous rocks at c. 965-950 Ma. Chemical discrimination diagrams and Hf and Nd isotope data together suggest that the protoliths of the mafic meta-igneous rocks were emplaced as relatively juvenile crustal contributions in an active plate margin. Zircon growth at c. 920 Ma within the Yell Sound Group correlates with high-grade metamorphism documented previously in Shetland. Further zircon growth and Pb loss at c. 470-460 Ma indicates overprinting during the Ordovician Grampian orogenic event. Similar age successions of Ellesmere Island, Svalbard and East Greenland also contain evidence for Tonian magmatism (some calc-alkaline), deformation and metamorphism. The new data favour Rodinia reconstructions that incorporate subduction-related magmatism and associated tectonism along the margin of NE Laurentia during the Tonian. The Yell Sound Group and correlative peri-Laurentian successions were intruded by subduction-related magmas and deformed and metamorphosed during development of the Valhalla exterior accretionary orogen, part of a more extensive peri-Rodinian subduction system.

We document newly recognized Late Ordovician high-pressure (HP) metamorphism in the Scottish Caledonides. Garnet growth at ca. 455-445 Ma has been previously ported from across the Northern Highland Terrane (NHT) and Shetland, yet the metamorphic conditions are unknown and the tectonic drivers associated with this event are controversial. Here we show that garnets dated at ca. 449 Ma within metabasic rocks on the Ross of Mull (southwestern peninsula of the Isle of Mull, Scotland, UK, within the NHT) grew at pressures >0.9 GPa, associated with the formation of kyanite-bearing assemblages in meta-pelites that equilibrated at peak conditions of 1.0-1.3 GPa and 740-780 degrees C. This requires the burial rock to-40-45 km depth, and the addition of this (now removed) overburden suggests that the crust reached-70 km in thickness, enough to support a region of high topography-6 km in elevation. The timing of this crustal thickening episode post-dated Late Cambrian-Early Ordovician Grampian arc-continent collision, but predated the nal Silurian closure of the Iapetus Ocean, south of the Midland Valley. The presence similar garnet-bearing amphibolites dated ca. 455-445 Ma on the Scottish north coast and Shetland suggests that this period HP metamorphism was a regional feature across the NHT and Shetland. It was followed by Scandian nappe stacking and lower pressure metamorphism at ca. 444-415 Ma, potentially forming a single protracted orogenic phase prior to the final closure of Iapetus. There are several potential drivers for the Late Ordovician event, including (1) subduction flip south of the Midland Valley Terrane to NW-directed subduction followed by collision of cryptic outboard terranes and/ or Baltica followed by large magnitude sinistral strike slip along the Great Glen Fault, (2) continued SE-directed subduction and collision of the Midland Valley terrane with Laurentia, or (3) subduction-flip followed by NW-directed flat slab subduction causing protracted accretionary orogenesis without necessarily requiring either collision with Baltica or large-scale strike slip displacements along the Great Glen Fault. Irrespective of the preferred tectonic model, the climax of Caledonian orogenesis in Scotland predated terminal continental collision.

The Neoarchaean foreland basement of the Faroe-Shetland terrane (FST) displays abundant evidence for isotopic resetting of U-Pb systems in apatite between c. 1800 and 200 Ma, interpreted to result from episodic heating pulses associated with regional scale tectonic events. Major apparent age peaks of c. 1800-1600 Ma broadly correspond to the timing of Nagssugtoqidian-Laxfordian orogenesis >225 km further south. These are thought to reflect widespread heating during late- to post-orogenic delamination that affected a wide area of the orogenic foreland and resulted in a low-middle greenschist facies static overprint, affecting much of the FST basement. Late- to post-orogenic delamination might also account for major apparent age peaks at c. 1300-1100, 800, and 500-400 Ma, corresponding to, respectively, Grenvillian, Knoydartian and Caledonian orogenic events. However, east-dipping seismic reflectors in the basement west of Shetland may represent the northward extension of the Grenvillian Outer Hebrides Thrust (Zone) and/or Caledonian thrusts and so perturbation of isotherms during west-directed thrusting could therefore also account for these apparent age peaks. Minor apparent age peaks of c. 700, 600, 350 and 200 Ma are most easily interpreted as resulting from enhanced heat flux that accompanied periods of crustal extension prior to and following the Caledonian orogeny.

Using Gondwana as an example, we show how the geological record can be interrogated to detect significant changes in mantle convection patterns at critical junctures in Earth's evolution. Evidence of major changes in mantle circulation in the aftermath of late Neoproterozoic-early Paleozoic Gondwana assembly is provided by widespread (i) plume-related magmatism around Gondwana's periphery, (ii) ironstone deposits related to mantle plume-ocean ridge interaction and enhanced hydrothermal activity, and (iii) super-mature clastic deposits that reflect epeirogenic uplift triggered by mantle upwelling beneath Gondwana combined with deep tropical weathering. In our model, Gondwana assembled above a region of mantle downwelling in which subducted slabs between the converging Gondwanan continents descended to the core-mantle boundary. Renewed subduction along Gondwana's periphery yielded early arc magmas. But as downwelling beneath Gondwana evolved into upwelling as a result of the ponding of subducted slabs at the base of the mantle, mantle plumes rose from the margins of the nascent upwelling to interact with the edges of Gondwana, where they penetrated the peripheral subduction zones via slab windows, tears and transform faults to generate voluminous calc-alkalic crustal melts in hydrated arc regions and A-type magmas in dry back-arc regions. The plumes also underplated oceanic lithosphere and interacted with adjacent ocean ridges, thereby enhancing hydrothermal activity and the flux of bioessential nutrients, leading to the recurrence of marine iron-rich sedimentary rocks in the geological record. At the same time, upwelling beneath a tropical to equatorial Gondwana led to epeirogenic uplift, deep weathering and erosion, resulting in the production of widespread super-mature clastic deposits. We contend that major changes in mantle convection patterns were encoded into the geological record of Gondwana assembly, influenced global-scale mantle convection patterns, and should be incorporated into geodynamic models for the assembly of Pangea. (c) 2023 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.

U–Pb apatite geochronology is increasingly recognized as a valuable tool for constraining the age of mid-crustal ductile shear zones. The crustal-scale Outer Hebrides Fault Zone (OHFZ) within the Laurentian foreland of the Scottish Caledonides has long been of uncertain age and tectonic significance. Earliest deformation within the OHFZ was associated with top-to-the-NW ductile thrusting that formed a belt of greenschist facies mylonites within host Archean−Paleoproterozoic basement gneisses. Previous estimates for the timing of thrusting vary between c . 1600 Ma and c . 430 Ma. The mylonitic fabrics are defined by a recrystallized assemblage of quartz + albite/oligoclase + sericite + actinolite + epidote + apatite ± calcite, consistent with deformation temperatures of 400–500°C and within the range of reported closure temperatures for Pb diffusion in apatite. U–Pb (LA−ICP−MS) dating of two texturally distinct apatite grain types within the mylonites has yielded ages mostly in the range c . 1100–900 Ma. The OHFZ is therefore interpreted as a Grenville–Sveconorwegian structure that formed during the tripartite collision of Laurentia, Baltica, and Amazonia and the assembly of Rodinia. Supplementary material : U–Pb isotopic data (Table S1), trace element data (Table S2) and laser ablation spot images are available at https://doi.org/10.6084/m9.figshare.c.7084925

Late Tonian (ca. 735 Ma) A-type granite magmatism accompanied the development of a rifted continental margin in the southwestern portion of the S & atilde;o Francisco paleocontinent. Zircon U-Pb and trace elements, whole-rock lithogeochemistry, and Nd-Sr isotopes enable assessment of the tectonic setting. The Araras Granite shows high silica content (between 73 and 76 %) and ferroan character. The Y + Nb and Yb + Ta parameters vary respectively between 73 to 212 ppm, and 8.3 to 19.1 ppm, and the 1000*Ga/Al ratio varies between 2.6 and 3.4. Zircon U-Pb data indicates a crystallization age of 736 +/- 12 Ma. The epsilon Nd-(t) is slightly negative (between -3.6 and -1.7), and the depleted mantle model ages (T-DM) range between 1.26 and 1.56 Ga. Binary mixing models based on whole-rock element and isotope geochemistry indicate that the granite was formed by mixing melts derived from two sources: a lithospheric mantle component and Paleoproterozoic magmatic arc rocks from the regional basement. The Araras Granite is concluded to represent a late stage of extension-related intraplate magmatism between ca. 840 and 730 Ma, associated with the evolution of a rifted continental margin in the southwestern S & atilde;o Francisco paleocontinent. Intraplate magmatism was partially synchronous with documented magmatic pulses within long-lived island arc systems that surrounded the paleocontinent. Extensional episodes in the rifted passive margin may be related to slab-pull forces driven by the outboard subduction dynamics.

A tribute to the career of J. Brendan Murphy, this volume covers topics that encompass the three main fields of his influence: (i) supercontinents and the supercontinent cycle; (ii) orogenesis and terranes; and (iii) magmatism and magmatic processes. Papers range from strongly field-based studies to conceptual analyses, and focus on clarifying some crucial geological processes.

Transitioning tectonic regimes from stagnant lid to plate tectonic models is still challenging. This tectonic transition appears to be diachronic in different old cratonic blocks worldwide. One key point to address tectonic models in early Earth is the appearance of the TTG-sanukitoid associations, which are interpreted as the products of melting oceanic slabs and melting of the hydrated mantle wedge in supra subduction zones. Although typical of the Archean, this association persists until the Paleoproterozoic in some cratonic remnants of South America. The Minas-Bahia Orogen (MBO) is one of the most extensive Paleoproterozoic belts of Brazil, cropping out in the Sao o Francisco Craton but also as reworked thrust slices within surrounding Neoproterozoic belts. Here, we explore the southern part of MBO, bringing new geochemical, U-Pb zircon geochronology (LA-ICP-MS) and Nd and Sr isotopic data of the Juiz de Fora Complex that constitutes the external magmatic arc system of this Siderian to Orosirian orogen. Granodioritic to tonalitic orthogranulites with TTG geochemical signatures, crystallization ages of ca. 2.21 and 2.14 Ga, with positive epsilon Ndi i (+2.9 to + 5.9) and 87 Sr/ 86 Sr i ratios between 0.7022 and 0.7045; Quartz-dioritic to granodioritic orthogranulites with sanukitoid composition, displaying crystallization ages between ca. 2.21 and 2.18 Ga, with near-chondritic epsilon Ndi i values of-2.43 to + 0.39, and 87 Sr/ 86 Sr i ratios between 0.7076 and 0.7179. Integrating the new data with previously published analyses allows us to envisage a comprehensive tectonic evolution model starting in an intra-oceanic setting and progressively evolving to a continental magmatic arc environment along the Rhyacian period. Integrated geochronology data indicates coeval and continuous generation of TTG and sanukitoid magmas for 160 Myr. Initially, with more juvenile contribution (ca. 2.22-2.15 Ga), that evolves progressively to a more mature stage (2.15--2.06 Ga). Additionally, two groups of mafic rocks, with ages of ca. 2.16 (OIB-like) and ca. 2.14 Ga (E-MORB), fill the gap between these two stages and possibly reflect arc migration and upwelling of the asthenosphere. Finally, data suggests the operation of plate tectonic processes since the Rhyacian, within this accretionary segment of the MBO, that ultimately resulted in the building of the Sao o Francisco Paleocontinent.