The juvenile Neoproterozoic basement of the Arabian Shield is overlain with angular unconformity by a voluminous Cambro-Ordovician cover sequence known as the Saq Formation and Wajid Group. Provenance studies of this vast siliciclastic cover over the Saudi Arabian part of the Arabian-Nubian Shield (ANS) have to date been based solely on U-Pb zircon data and heavy minerals. We present the first combined in-situ U-Pb, δ¹⁸O and Lu-Hf isotopic data for detrital zircon from the Saq and Wajid units exposed along the northeastern margin and southern part of the Arabian Shield. U-Pb age spectra reveal prominent age peaks at ca. 0.8–0.55 Ga and 1.1–0.9 Ga with subordinate peaks at ca. 2.2–1.7 Ga and 2.7–2.5 Ga. The δ¹⁸O secular variation mirrors global compilations with Archaean zircon defining a restricted δ¹⁸O range of ca. 4.0–8.0 ‰ and younger zircon showing wide variation in δ¹⁸O up to ca. 14 ‰. The ca. 0.8–0.55 Ga age peak has the largest variation in ε_Hf(t) with about half of all these Neoproterozoic zircon grains being juvenile (ε_Hf(t) > 5), which are interpreted to be sourced from the juvenile terranes of the ANS. Neoproterozoic zircon with evolved ε_Hf(t) signatures require a more distal source beyond the ANS. As extensive ca. 1.1–0.9 Ga crust is lacking in the vicinity of the ANS, the ca. 1.1–0.9 Ga age peak is interpreted to be derived from either contemporaneous orogenic belts in Central Africa or recycled from older sedimentary rocks containing these age components. Extreme variations in δ¹⁸O of post–Archaean zircon, together with the evolved ε_Hf(t), indicate crustal thickening and increased incorporation of supracrustal material associated with collisional orogenesis. The remarkable similarities in age spectra and isotopic compositions of the Saq Formation and Wajid Group sandstones with those from other regions in northern Gondwana indicate a continental–scale homogenization and dispersion process.

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 ϵNd(t) (-9.22 to -8.87) and ϵHf(t) (-11.8 to -6.49), combined with high (87Sr/86Sr)i (0.7099-0.7109) and δ18Ozrn (+9.99‰ to +10.9‰), 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 (~20-30%) and the Asian plate (~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 ϵNd(t) (-7.46 to -6.88) and ϵHf(t) (-11.9 to -5.80), along with high (87Sr/86Sr)i (0.7091-0.7092) and δ18Ozrn (+8.75‰ to +10.7‰), 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 Yukon–Koyukuk Basin is a wide, triangular depression in northern Alaska that initiated as the consequence of the collision between an intraoceanic arc and the Arctic Alaska margin. It is bordered by the metamorphic terranes of the Seaward Peninsula, the Brooks Range and the Ruby Terrane. The Yukon–Koyukuk Basin is divided into two sub-basins separated by remnants of the volcanic arc. Two different models have been suggested for its formation. One model interprets the Yukon–Koyukuk Basin to have formed during collision in a forearc–backarc setting, while the other favours an extensional regime that was active after the cessation of collision. To test the two models, ten sedimentary samples from the two stratigraphically lowest units cropping out along the middle reaches of the Koyukuk River were analysed. Point counting and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN^®) are used to evaluate sedimentary provenance. This study also presents zircon U–Pb ages from three interbedded tuffaceous layers to better constrain the age of the units. The base of the succession indicates a volcanic source (enriched in clinopyroxene) deposited at ca 138.3 ± 0.8 Ma (2σ), while younger overlying strata are dominated by metamorphic input (enriched in garnet and epidote) reflecting the erosion of the surrounding metamorphic terranes at ca 112.6 ± 1.1 Ma (2σ). The application of a multi-method provenance approach has been essential in constraining the formation and evolution of the northern Yukon–Koyukuk Basin. This is of significant importance for advancing the understanding of Alaskan geology and for providing insights into modern basins within analogous tectonic settings, such as the Banda Arc in Southeast Asia.

The juxtaposition of the composite Pearya terrane and the northern Laurentian margin at Ellesmere Island, Nunavut, Canada, has significant ramifications for the Paleozoic tectonic history of the circum-Arctic region. Published tectonic models rely upon interpretation of the subduction-related Kulutingwak Formation as an indicator of Ordovician and/or Silurian accretion (Trettin, 1998). New igneous and detrital zircon U-Pb and Lu-Hf isotopic data from 16 samples collected in the Yelverton Inlet–Kulutingwak Fiord region of northern Ellesmere Island suggest that the Kulutingwak Formation of Trettin (1998) contains structural blocks derived from both the Pearya terrane and Silurian strata associated with the ancestral Laurentian margin. Data from this study demonstrate a complex provenance history for rocks within the Petersen Bay, Kulutingwak Fiord, and Emma Fiord fault zones, with age probability peaks of ca. 470 Ma, 650 Ma, and 960–980 Ma that suggest affinity with the Pearya terrane, and age probability peaks of ca. 1800 Ma and 2700 Ma that indicate connections to the Laurentian margin. The combination of these signatures in Kulutingwak Formation rocks suggests that the Pearya terrane was proximal to the northern Laurentian margin by Late Ordovician time. Silurian and younger strike-slip displacement on the major fault zones resulted in the incorporation of blocks derived from the Pearya terrane basement and Silurian clastic rocks into the Kulutingwak Formation. Silurian displacement along these strike-slip faults, which are integral components of the Canadian Arctic transform system, is recorded by syndepositional deformation structures in the Danish River Formation and prevented the transition from soft to hard collision of the Pearya terrane. The two-stage model for the Pearya terrane—accretion followed by significant translation—provides a process for developing complex steep terrane boundaries with contentious displacement histories that are common in accretionary orogens.

Radiogenic isotopes serve as a crucial tool for investigating crustal evolution, playing a pivotal role in revealing magma sources and petrogenesis. However, they can be ineffective in distinguishing between distinct magmatic sources with similar radiogenic isotopic compositions, a common occurrence in nature. Here we addresse this challenge in the Ordovician igneous rocks from the West Kunlun orogenic belt (WKOB), aiming to distinguish between two potential magmatic sources (i.e. the Tarim Craton and the Tianshuihai terrane) with similar isotopic compositions using appropriate thermodynamic and geochemical modeling based on mineral and whole-rock geochemistry. Zircon U–Pb dating yields ages of 483 ± 3 Ma for the Pushou gabbros and 469 ± 2 Ma and 461 ± 2 Ma for the Datong monzogranites and syenites, respectively. The Pushou gabbros exhibit low SiO₂ (47.4–49.1 wt %), high MgO (5.5–6.9 wt %), high large-ion lithophile elements (LILEs, e.g. Rb, Ba, Th, and K), and low high field-strength elements (HFSEs, e.g. Nb, Ta, Zr, Hf, P, and Ti), suggesting an origin in subduction-modified mantle. They display high whole-rock (⁸⁷Sr/⁸⁶Sr)_i ratios (0.7156 to 0.7192), negative whole-rock εNd(t) values (−7.1 to −7.8), as well as high zircon δ¹⁸O values (7.6–7.9‰) and enriched zircon Hf isotopic compositions (εHf(t) = −5.3 to −7.7), which are consistent with 1–5% subducted sediments in an enriched mantle source. Trace element models further confirm that the gabbros are most likely derived from low-degree (~15%) partial melting of subduction-modified Tarim mantle in the spinel–garnet facies rather than from the Tianshuihai mantle. The Datong syenites belong to the shoshonitic series and are characterized by medium SiO₂ (59.5–61.4 wt %), relatively low MgO (0.9–1.2 wt %) and Mg^# (37–42), enrichment in LILEs and depletion in HFSEs. They have high whole-rock (⁸⁷Sr/⁸⁶Sr)_i ratios (0.7103 to 0.7105) and negative whole-rock εNd(t) values (−3.8 to −4.3), along with negative to slightly positive zircon εHf(t) values (−3.8 to +2.6), similar to coeval mafic rocks. Thermodynamic and geochemical modeling suggest that the Datong shoshonitic rocks likely originated via crystal fractionation of shoshonitic basaltic magmas in the SW Tarim Craton. The Datong monzogranites have high SiO₂ (69.7–72.6 wt %), low MgO (0.6–0.7 wt %), and a typical enrichment in alkalis, Zr, and Nb, with depletion in Sr, P, and Ti, consistent with A-type granites. They are characterized by high whole-rock (⁸⁷Sr/⁸⁶Sr)_i ratios (0.7321 to 0.7323), negative whole-rock εNd(t) values (−11.3 to −11.8), negative zircon εHf(t) values (−11.0 to −16.5), and high zircon δ¹⁸O values (7.2–8.0‰), indicating derivation from the remelting of an ancient crustal source. Thermodynamic, major, and trace element modeling indicate that their parent magma may have been generated by water-deficient (~2 wt %) partial melting of ancient crustal material beneath the SW Tarim Craton rather than that of the Tianshuihai terrane, under high-temperature (T > ~950°C) and low-pressure (P = 5–8 kbar) conditions. Based on the tectonic framework of the WKOB, we propose that the original mantle and crust beneath the southern Kunlun terrane may have been modified or partially replaced by that beneath the SW Tarim Craton during the Ordovician. Therefore, this evidence for Tarim-derived magmatism, when combined with regional sedimentary and structural records, indicates that Ordovician magmatism in the southern Kunlun terrane is most consistent with episodic northward subduction of the Proto-Tethys Ocean, commencing at ~485 Ma. Middle Ordovician slab break-off can explain the formation of the A-type granites, but reinstated northward subduction is required for the generation of late Ordovician Datong syenites.

The Cretaceous High Arctic Large Igneous Province (HALIP) in Canada involved extrusion of continental flood basalts (CFBs) at 130-120 Ma and 100-95 Ma and emplacement of an extensive sill and dike network that intersected the Carboniferous to Paleogene Sverdrup Basin. In this paper, we present new Ar-40/Ar-39 ages, major and trace elements, and Sr-Nd-Pb isotope ratios for HALIP lava, dikes, and sills from Bukken Fiord, NW Axel Heiberg Island, Canadian Arctic Islands. Our best constrained Ar-40/(39) ages yield a weighted average of 124.1 +/- 1 (2 sigma) Ma, coincident with the first pulse of tholeiitic CFB magmatism in the Arctic-wide HALIP as exemplified by Isachsen Formation flood basalts on Axel Heiberg Island. The Bukken Fiord samples are plagioclase and clinopyroxene-phyric tholeiitic basalts, are relatively evolved (3.2-6.5 wt% MgO), and share similar major and trace element compositions to typical HALIP tholeiites. Initial Nd-143/Nd-144 ranges from 0.51260 to 0.51291 and initial Sr-87/Sr-86 ranges from 0.70362 to 0.70776, while measured Pb-206/Pb-204, Pb-207/Pb-204, and Pb-208/Pb-204 range from 18.614 to 19.199, 15.534 to 15.630, and 38.404 to 39.054, respectively. The most primitive sample in this study has Sr-Nd-Pb isotope signatures that suggest an enriched plume-derived mantle source for HALIP tholeiites. Most samples, however, possess relatively radiogenic isotope signatures that can be explained by moderate degrees of assimilation of Sverdrup Basin sedimentary rocks. Magma-crust interaction in the HALIP plumbing system was likely widespread and may have increased the environmental impact of the HALIP, particularly if crustal carbon was volatilized.

Egypt hosts numerous rare-metal granites, i.e., highly evolved granites enriched in rare metals (Ta, Nb, Be, Sn, Zr, Th, and REE). However, the processes involved in the rare-metal enrichment are not fully understood. We present new data on the textural characteristics and chemical composition of rare-metal mineralization associated with microgranite dikes in the Ras Abdah area of the Egyptian Eastern Desert. These dikes are garnet-bearing leucogranites (GLG) composed of perthitic alkali-feldspars and quartz. When compared to other Egyptian A-type granites, microgranite dikes are alkaline rocks with particularly higher HREE contents. Zircon, huttonite, fergusonite (Y), and Fe-Ti-Zn oxides (magnetite, Zn-bearing ilmenite and pyrophanite) are largely associated with the altered domains, which are also enriched in Nb, Zr, Y, Ta, Th, and REE. However, similarities between the chondrite-normalized REE patterns of the altered and unaltered domains of the GLG dikes favor the hypothesis of a unique magmatic signature. Moreover, the chemical and textural features of rare-metal minerals indicate that the alteration of primary minerals was caused by deuteric fluids or aqueous residual melt exsolved from the parental granitic magma (autometasomatism). Garnet compositions are rich in the spessartine component (up to 84 %), which is typical of garnet in highly evolved pegmatitic rocks. Furthermore, garnet exhibits no major element zoning but shows chemical fluctuations in trace element concentrations, suggesting correspondingly abrupt changes in melt composition due to sequential magma pulsing. This magma emplacement may cause crystal nucleation and oscillatory crystallization followed by magmatic segregation. Overall, parental magma type, dike injection, and magmatic-hydrothermal processes all play a role in the unusual enrichments of rare metals.

In northern Alaska, the Early Cretaceous sedimentary Yukon-Koyukuk basin documents the progressive unroofing of the adjacent Brooks Range orogen. Igneous clasts in the lower conglomerate are believed to originate from ophiolitic rocks of the two uppermost allochthons in the Brooks Range, the Brooks Range ophiolite and the Angayucham terrane. The emplacement of these oceanic terranes onto the continental margin of the Arctic Alaska terrane documents the initiation of Brookian orogenesis. While most agree that the Angayucham terrane represents a widespread distribution of Late Devonian oceanic crust and Triassic-Early Jurassic oceanic plateau(s)/island(s), the age and origin of the Brooks Range ophiolite remains controversial. We present new age, whole-rock chemistry, and isotopic data from igneous clasts as well as a few Angayucham terrane outcrop samples from the NE Yukon-Koyukuk basin. Our results show that the igneous clasts are mostly subduction-related and more likely to represent eroded material from the Brooks Range ophiolite rather than the Angayucham terrane. Our Late Triassic, and Early and Middle Jurassic zircon crystallization ages for the igneous clasts, combined with their immobile trace element compositions documenting various stages of oceanic subduction (mature arc and later rifting), suggest a long-lived subduction system that was active in the Late Triassic and throughout the Middle Jurassic. Radiogenic lead and neodymium isotopic results yield juvenile signatures for both the igneous clasts and the Angayucham terrane, pointing to their formation in an intraoceanic setting distal from the continental rocks and sediments of the Arctic Alaska terrane. These new data, combined with the published data of others, allow us to propose a revised tectonic model that integrates Late Triassic island arc formation with the tectonic development and emplacement of the Brooks Range ophiolite.

New U-Pb zircon geochronology using high-spatial resolution secondary ion mass spectrometry fills a data gap and provides crystallization ages for granitoids from the Asir composite terrane in the southernmost Arabian Shield of Saudi Arabia. Ages of c. 810–685 Ma, c. 663–636 Ma, and 625–610 Ma reflect oceanic island arc genesis, subduction-related arc accretion (syn-collisional), and post-collisional stabilization, respectively. All samples have juvenile ε_Nd(t) compositions with no evidence of older material being involved in their genesis, indicating that this part of the Arabian Shield grew through juvenile magmatic addition and that assimilation by syn- and post-tectonic magmatism involved an isotopically juvenile component(s). The crustal thickness derived from the (La/Yb)_N proxy indicates significant thickening from 10–20 km to c. 70 km at c. 650 Ma, consistent with timing of orogenic uplift and increasing crustal thickness post-dating peak Nabitah orogeny. The age of an intrusion cross-cutting the Atura formation, when combined with other data, provides a well-constrained depositional age of c. 646–625 Ma for the Atura formation and indicates that erosion of the orogenic edifice in this part of the Arabian Shield began at latest by 625 Ma. Our new data indicate that denudation occurred 80–100 m.y. before the development of the prominent sub-Cambrian peneplain, consistent with previous assertions that major pulses of denudation occurred prior to the waning stages of Nabitah orogenesis.

The concept of the ‘magma series’ and the distinction between alkaline, calc-alkaline and tholeiitic trends has been a cornerstone in igneous petrology since the early 20^th century, and encodes fundamental information about the redox state of divergent and convergent plate tectonic settings. We show that the ‘Bowen and Fenner trends’ that characterise the calc-alkaline and tholeiitic types of magmatic environments can be approximated by a simple log ratio model based on three coupled exponential decay functions, for A = Na₂O + K₂O, F = FeO_T and M = MgO, respectively. We use this simple natural law to define a ‘Bowen-Fenner Index’ to quantify the degree to which an igneous rock belongs to either magma series. Applying our model to a data compilation of igneous rocks from Iceland and the Cascade Mountains effectively separates these into tholeiitic and calc-alkaline trends. However the simple model fails to capture the distinct dog-leg that characterises the tholeiitic log ratio evolution, which can be attributed to the switch from ferrous to ferric iron-bearing minerals. Parameterising this switch in a two stage magma evolution model results in a more accurate fit to the Icelandic data. The same two stage model can also be fitted in A–T–M space, where ‘T’ stands for TiO₂. This produces a new way to identify calc-alkaline and tholeiitic rocks that does not require the conversion of FeO and Fe₂O₃ to FeO_T. Our results demonstrate that log ratio analysis provides a natural way to parameterise physical processes that give rise to these magma series.