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Tectonic interpretations of arc remnants in the Himalayan orogen remain uncertain, despite their important implications for the overall convergence history between India and Eurasia. Provenance results from deep‐water volcaniclastic rocks of the Indus Suture Zone in Ladakh provide new constraints on the Mesozoic tectonic evolution of the Dras and Kohistan‐Ladakh arcs. Detrital zircon (DZ) U‐Pb ages and whole‐rock geochemistry of the fault‐bounded Upper Cretaceous Nindam and Paleocene Jurutze formations present age patterns and compositions that are consistent with those of the Dras and Kohistan‐Ladakh arcs, respectively. The combination of DZs of the Nindam and Jurutze formations with the igneous zircons of the Dras and Kohistan‐Ladakh arcs shows similar age distributions that support a Late Jurassic to Paleocene tectonic connection between all these units. We argue that the secular trends in geochemical composition of DZs and volcaniclastic material are consistent with the magmatic evolution of one convergent margin, which shifted from a primitive to a mature stage during the Late Cretaceous. The recognition of a single Dras‐Kohistan‐Ladakh arc sets the stage for reevaluating competing scenarios of the Mesozoic evolution of the India–Eurasia convergent system. We find that the most likely scenario is that of a Jurassic arc formed above a south‐dipping intraoceanic subduction zone and accreted to Eurasia during the Early Cretaceous, after which it evolved above a north‐dipping subduction zone. Plain Language Summary The Himalayan orogen is the result of the collision between India and Eurasia and the closure of the intervening Neotethys Ocean. The suture zone between India and Eurasia hosts an incomplete and complex archive of the paleogeography that once existed between them prior to continent‐continent collision. Investigating suture zone rocks may therefore provide valuable information on the building blocks of the orogen and the overall history of the India‐Eurasia convergent system. Disparate remnants exposed in the Indus Suture Zone (Western Himalaya) suggest that volcanic arcs and sedimentary basins were formed above intraoceanic subduction zones, but there is no consensus on their original paleogeography. We discuss new and existing geological data from volcaniclastic rocks related to the Dras and Kohistan‐Ladakh arcs. Our data support the existence of a single Dras‐Kohistan‐Ladakh arc during the Mesozoic and provide additional insights into the complexity of the pre‐collisional convergence between India and Eurasia. Key Points Dissimilar ages and compositions of volcaniclastic units in the Indus Suture Zone reveal arc evolution from primitive to mature stages Detrital zircon U‐Pb ages and geochemistry, and whole‐rock geochemistry support a common origin of the Dras and Kohistan‐Ladakh arcs The recognition of a single Dras‐Kohistan‐Ladakh arc represents a key constraint in models of India‐Eurasia convergence

We report on the isotopic compositions of the Jurassic supra-subduction zone Evros ophiolite mafic rocks exposed in the eastern Circum-Rhodope Belt of northeastern Greece. These mafic units consist of low-Ti gabbroic and basaltic rocks, whose Nd–Sr–Pb isotopes are compatible with dominant mantle-derived MORB component mixed with a detectable amount of crustal material and/or sediment invoved in their melt source in the subduction zone. These isotopic features are consistent with an intra-oceanic arc origin of the mafic ophiolite rocks, and the Evros ophiolite Nd and Pb isotopes are comparable to those of the counterpart mafic rocks from the Mandritsa unit in Bulgaria.

The Dom Feliciano Belt is the South American part of an extensive Neoproterozoic orogenic system that developed during the late Cryogenian–early Cambrian close to the margin of southwest Gondwana. The link of its evolution with the tectonic processes in its African counterpart is still not well understood. P–T estimates, Lu–Hf garnet–whole-rock ages, U–Pb monazite SIMS ages and REE garnet and monazite data from samples of the Porongos and Passo Feio complexes indicate diachronous tectonic evolution of the central Dom Feliciano Belt foreland. Metasedimentary rocks of the eastern Porongos Complex reached previously estimated metamorphic peak conditions of ~ 560–580 °C and 5.8–6.3 kbar at 654 ± 2 Ma, based on Lu–Hf isochron garnet–whole-rock age data. This episode represents an early orogenic thickening in the foreland as a response to the beginning of the transpressive convergent evolution of the belt. The monazite age of 614 ± 6 Ma (U–Pb SIMS) is interpreted as associated with post-exhumation magmatic activity in the foreland and suggests that the eastern Porongos Complex was exhumed sometime between ca. 660 and 615 Ma. The main metamorphic and deformation event in the Porongos Complex’s western region occurred at ~ 545–565 °C and 4.3–5.3 kbar at 563 ± 1 Ma (garnet–whole-rock Lu–Hf isochron age). The exhumation of this part of the foreland is dated using monazite crystallising during garnet breakdown and suggests retrograde metamorphism at 541 ± 7 Ma (U–Pb SIMS). The main metamorphic fabric in the Passo Feio Complex further to the west developed at 571 ± 2 Ma (garnet–whole-rock Lu–Hf isochron age) at 560–580 °C and 4.7–6.4 kbar. The western part of the Porongos Complex and the Passo Feio Complex have deformed at similar P–T conditions and apparent geothermal gradients at ca. 570–565 Ma. These regions record a second crustal thickening event in the Dom Feliciano Belt foreland and the orogenic front migration towards the west as a response to the onset of crustal thickening on the African side of this long-lived transpressive orogenic system

Ten rock samples consisting of one pyroclastic density current (PDC1) deposit, seven lava flows (LF1–7), and two summit lava domes (LD1, 2) were studied to understand the petrogenesis and magma dynamics at Mt. Sumbing. The stratigraphy is arranged as LF1, PDC1, LF2, LF3, LF4, LF5, LF6, LF7, LD1, and LD2; furthermore, these rocks were divided into two types. Type I, observed in the oldest (LF1) sample, has poor MgO and high Ba/Nb, Th/Yb and Sr. The remaining samples (PDC1–LD2) represent type II, characterized by high MgO and low Ba/Nb, Th/Yb and Sr values. We suggest that type I is derived from AOC (altered oceanic crust)-rich melts that underwent significant crustal assimilation, while type II originates from mantle-rich melts with less significant crustal assimilation. The early stage of type II magma (PDC1–LF3) was considered a closed system, evolving basaltic andesite into andesite (55.0–60.2 wt% SiO 2 ) with a progressively increasing phenocryst (0.30–0.48 ϕ PC ) and decreasing crystal size distribution (CSD) slope (from − 3.9 to − 2.9). The evidence of fluctuating silica and phenocryst contents (between 55.9–59.7 wt% and 0.25–0.41 ϕ PC , respectively), coupled with the kinked and steep (from − 5.0 to − 3.3) CSD curves imply the interchanging condition between open (i.e., magma mixing) and closed magmatic systems during the middle stage (LF4–LF6). Finally, it underwent to closed system again during the final stage (LF7–LD2) because the magma reached dacitic composition (at most 68.9 wt% SiO 2 ) with abundant phenocryst (0.38–0.45 ϕ PC ) and gentle CSD slope (from − 4.1 to − 1.2).

In the northern part of the Marrakech High Atlas (MHA), along the southern Variscan segment of the Western Meseta, a Variscan granitic intrusion crops out, intruding metasediments and meta-volcanosedimentary rocks of Early Cambrian to Ordovician age. A new whole-rock Rb-Sr isochron age of 268 ± 9 Ma for the granite, combined with a previously published whole-rock Rb-Sr radiometric dating (271 ± 3 Ma), reveals a post-kinematic (tectonic) character with regard to the main Variscan deformational event, belonging within the tectonic context of the Moroccan Variscan orogenic belt. Geochemically, the Azegour intrusion is metaluminous to peraluminous and exhibits a calc-alkaline affinity with a ferruginous composition. The massif shows an extremely differentiated character (SiO = 77.53–78.14 per cent), K O and high total alkali contents, FeO /(FeO + MgO) and Ga/Al ratios, which have typical characteristics of an A-type granite. In addition, the granite contains high concentrations of LREE (La /Sm = 7.9–13.67) relative to HREE (La /Yb = 4.81–11.61) and a well-defined Eu negative anomaly (Eu/Eu* = 0.44–0.75). The granitic samples exhibit a strong enrichment of the most incompatible elements (Rb /Yb = 69.84–159.98) and a strong depletion of Ba, Sr, Eu, Nb, P and Ti. These characteristics are similar to those of A -type granites. The absence of mineralogy typical of an S-type granite, combined with its weakly peraluminous character [A/CNK (molar Al /CaO+Na O+K O) = 1,013–1,045], suggest that there is little or no significant involvement of supracrustal sources in the petrogenesis of the intrusion studied. Despite the strongly differentiated character of Azegour granitic rocks samples, their multi-element patterns shows many similarities to those of I-type granitoids, which has led to postulate that the parental liquids of A -type were derived from partial melting of mafic magmas. The representative samples studied show less depleted εNd values of −0.94 to −4.85 and lower positive to slightly negative εSr values of −1.45 to 9.32. The isotopic data suggest that the Azegour granite was emplaced 270 myr ago, apparently generated by partial melting of a mafic/intermediate magma source in the lower crust as a result of the underplating of the asthenosphere mantle-derived Oceanic Island Basalt-like magmas. Alternatively, their isotopic signatures also can be attributed to the interaction and/or hybridisation of basaltic liquids derived from the mantle with these lower crust materials. The generated parental magma probably occurred at deep structural levels and involved fractional crystallisation processes by the separation of a mineralogical association composed of plagioclase + potassium feldspar ± biotite ± amphibole ± sphene ± apatite. The whole-rock Rb-Sr age of 268 ± 9 Ma, whole-rock geochemistry and Sr-Nd isotopic compositions of εNd and εSr , combined with fieldwork data, suggest that the Azegour granite was emplaced during the later stage of compressional Variscan events in the MHA.

Indirect calculation of magma crystallization temperatures is an important subject for geologists to know the petrogenesis of igneous rocks. During magma evolution from generation to crystallization, several processes control the behavior of elements. In this research, we obtained two new methods for the thermometry of magma by using high field strength elements (HFSEs; Zr, Hf, Ce, Y, and Ti) abundances in igneous rocks. The first was T(K) = −15,993/(lnCZr + lnCHf − 21.668), where CZr and CHf are the bulk-rock Zr and Hf contents in ppm, and T is the temperature in Kelvin. This equation was specially formulated to address metaluminous to peraluminous rocks with M < 2 [(Na + K + 2Ca)/(Al × Si)] (cation ratio) and SiO2 > 63 wt.%. The second was T(K) = −20,914/(ln(CHf + CY + CCe) + (ln(CZr/TiO2) − 31.153). CHf, CY, and CCe, and CZr are Hf, Y, Ce, and Zr contents (ppm) in the whole rocks. The second equation is more suitable for peralkaline to alkaline rocks with M > 2 and a wide range of SiO2. Both equations are applicable for temperatures from 750 °C to 1400 °C. These two equations are simple and robust thermometry methods and predict similar values in the range of TZr thermometry, which has previously been suggested for magma crystallization temperature.

Ignimbrites are useful chronological markers in the geological record at local and regional scales. They also provide information on the dynamics of the eruption that produced them, making their study of great importance in terms of volcanic hazard assessment. However, their study is usually hampered by their lateral variation and discontinuity. When stratigraphic and lithologic criteria are not sufficient for correlation purposes, the use of multiple complementary correlation tools may be necessary to correctly determine their areal extension, volume and facies variations. Whole-rock geochemistry is considered one of the less reliable correlation techniques due to the pyroclastic nature of these deposits and their emplacement dynamics. These may introduce vertical and horizontal geochemical heterogeneity in the final deposit. In addition, the occurrence of zoned ignimbrites due to magma supply of changing composition is common. In this work we show that, if appropriately used, whole-rock geochemistry can be a valid and highly useful tool for ignimbrite correlation. We provide an example from the study of an ignimbrite sequence containing 18 units (sensu lato) in the Sulcis region (SW Sardinia, Italy). A protocol has been developed for unit recognition based on successive simple binary diagrams where the whole-rock composition of a problem sample can be plotted. Immobile trace elements have been preferentially used to minimize effects of element mobilization associated with alteration and weathering. The diagrams provided here are designed for the Sulcis, but the methodology followed to develop them may be applied to other study areas.

The Late Cretaceous Pandan Formation in Cebu Island is one of the oldest sedimentary units in the Central Philippines. The inconsistencies in geological descriptions and interpretation of the depositional environment of the Pandan Formation complicated efforts to determine the origin and tectonic history of the basement of Cebu Island. This study therefore looks into the petrological and geochemical characteristics of the Pandan Formation and their implications for the tectonic development of the Philippine Arc during the late Mesozoic. Petrographic analyses indicate significant contribution from mafic sources with additional inputs from felsic rocks, siliciclastics and metamorphic sources. Enrichment of detrital quartz from felsic volcanic and plutonic rocks, as well as from siliciclastic and metamorphic sources, has shifted the SiO2 composition of the Pandan clastics from a mafic to a more intermediate source. Whole‐rock geochemical analyses revealed low SiO2/Al2O3 = 4.21, low K2O/Na2O = 1.16, low Th/Sc = 0.13, low Th/U = 2.78, high La/Th = 4.51, significantly low REEs = ca 76.45 ppm and low LaN/YbN = 4.28. A slight negative chondrite‐normalized Eu/Eu* (0.91) anomaly and significantly high PAAS‐normalized positive Eu/Eu* (1.39) values are consistent with derivation from a young undissected magmatic arc terrane. Tectonic discrimination diagrams suggest formation in an oceanic island arc to active margin/collision zone modelled to be located at the oceanic leading edge of Australia. Rapid uplift and erosion of the magmatic arc and older allochthonous blocks gave way to the rapid deposition of the Pandan Formation in the Late Cretaceous at the subequatorial region. The Pandan Formation provides vital information on the Late Cretaceous evolution of Cebu Island in the Central Philippines. Collision of the proto‐Philippine arc with the East Philippine‐Daito arc modelled to be located at the oceanic leading edge of the Australian plate led to rapid uplift and erosion of the magmatic arc and continental derived sediments which gave way to deposition of the Pandan Formation in the Late Cretaceous at the subequatorial region.

In this paper we present new data on the spatial variability of peridotite composition across a kilometer-scale mantle shear zone within the Lanzo massif (Western Alps, Italy). The shear zone separates the central from the northern part of the massif. Plagioclase peridotite shows gradually increasing deformation towards the shear zone, from porphyroclastic to mylonitic textures in the central body, while the northern body is composed of porphyroclastic rocks. The peridotite displays a large range of compositions, from fertile peridotite to refractory harzburgite and dunite. Deformed peridotites (proto-mylonite and mylonites) tend to be compositionally more homogeneous and fertile than weakly deformed peridotites. The composition of most plagioclase peridotites show rather high and constant (Ce/Yb) N ratios, and Yb N that cannot be explained by any simple melting model. Instead, refertilization modeling, consisting of melt increments from spinel peridotite sources, particularly with E-MORB melt, reasonably reproduces the plagioclase peridotite whole rock composition. Combined with constraints from Ce–Nb and Ce–Th systematics, we speculate that peridotites such as those from Lanzo record pervasive refertilization processes in the thermal boundary layer. In this scenario, mantle shear zones might act as important areas of melt focusing in the upper mantle that separates the thermal boundary layer from the conductively cooled mantle.

In this paper, we present detailed field observations, chronological, geochemical and Sr–Nd isotopic data and discuss the petrogenetic aspects of two types of mafic dykes, of alkaline to subalkaline nature. The alkaline mafic dykes exhibit a cumulate to foliated texture and strike NW–SE, parallel to the main trend of the region. The Ar/ Ar amphibole age of 321.32 ± 0.55 Ma from an alkaline mafic dyke is interpreted as an indication of Carboniferous cooling through ca. 550 °C after intrusion of the dyke into the granitic Galeh-Doz orthogneiss and Amphibolite-Metagabbro units, the latter with Early Carboniferous amphibolite facies grade metamorphism and containing the Dare-Hedavand metagabbro with a similar Carboniferous age. The alkaline and subalkaline mafic dykes can be geochemically categorized into those with light REE-enriched patterns [(La/Yb) = 8.32–9.28] and others with a rather flat REE pattern [(La/Yb) = 1.16] and with a negative Nb anomaly. Together, the mafic dykes show oceanic island basalt to MORB geochemical signature, respectively. This is consistent, as well, with the (Tb/Yb) ratios. The alkaline mafic dykes were formed within an enriched mantle source at depths of ˃ 90 km, generating a suite of alkaline basalts. In comparison, the subalkaline mafic dykes were formed within more depleted mantle source at depths of ˂ 90 km. The subalkaline mafic dyke is characterized by Sr/ Sr ratio of 0.706 and positive ɛ (t) value of + 0.77, whereas Sr/ Sr ratio of 0.708 and ɛ (t) value of + 1.65 of the alkaline mafic dyke, consistent with the derivation from an enriched mantle source. There is no evidence that the mafic dykes were affected by significant crustal contamination during emplacement. Because of the similar age, the generation of magmas of alkaline mafic dykes and of the Dare-Hedavand metagabbro are assumed to reflect the same process of lithospheric or asthenospheric melting. Carboniferous back-arc rifting is the likely geodynamic setting of mafic dyke generation and emplacement. In contrast, the subalkaline mafic sill is likely related to the emplacement of the Jurassic Darijune gabbro.