International Geology Review

Marcos, Paulo; Hueck, Mathias; Oriolo, Sebastian; Renda, Emiliano Manuel; Arzadún, Guadalupe; González, Pablo Diego; Benedini, Leonardo; Geraldes, Mauro; Lovecchio, Juan Pablo; Rojas Vera, Emilio; Moreno, Franco

doi: 10.1080/00206814.2025.2523404pmid: N/A

The geodynamic evolution of the basement of the Patagonian Precordillera (Argentina) began with middle to late Paleozoic tectonometamorphic and magmatic events. Subsequent exhumation was triggered by brittle-ductile to brittle deformation from Mesozoic to Cenozoic times thought the thermal evolution of this stage is relatively unexplored in most basement areas. In this study, we assess the cooling-thermal evolution in the upper crust, providing new thermal models based on fission-track and (U-Th)/He thermochronology data in zircon and apatite belonging to basement inliers of the Patagonian Precordillera. Most thermal models show similar decreasing time-temperature paths (t-T), from which three stages are distinguished. The Late Triassic – Jurassic stage exhibits a rather undefined cooling trajectory and cooling rates (0.56–2.2°C/My), which are temporally correlated with high magmatic productivity and extensional deformation related to extensional tectonic settings. This first stage might have resulted from coupled tectonothermal processes consisting of extensional faulting and high-temperature gradient. Subsequently, a relatively fast temperature decrease (2.75–5°C/My) for the late Early Cretaceous to Paleocene is likely related to a compressive stage associated with the growth of the early Andean Orogen. Low cooling rates (<1°C/My) characterize the third stage correlative with Palaeogene arc magmatism. Although this low cooling rate remains until present day conditions, one thermal model denotes a final high cooling rate during Miocene linked to the second compression stage of the Andean Orogen. Results thus indicate that one of the most significant exhumation event recorded in basement rocks of the Patagonian Andean foreland took place during the late Early Cretaceous – Paleocene stage.

Abu El-Kheir, Tarek H.; Cai, Keda; Maurice, Ayman E.; Wang, Kai; Wang, Hairuo

doi: 10.1080/00206814.2025.2526080pmid: N/A

The Motaghairat layered mafic–ultramafic intrusion is part of the Neoproterozoic basement of the Eastern Desert of Egypt, constituting the northern tip of the juvenile Arabian-Nubian Shield (ANS). This intrusion exhibits a well-differentiated rock association, comprising, from bottom to top, dunite, harzburgite, lherzolite, orthopyroxenite, troctolite, olivine gabbro, and gabbro. Textural features, mineral compositions of olivine, pyroxene, and Cr-spinel, along with whole-rock geochemical data, collectively suggest that these rocks represent cumulates differentiated from a tholeiitic magma, essentially by fractional crystallization. The trace element patterns of pyroxenes, amphiboles, whole-rock samples, and calculated melts in equilibrium with clinopyroxene and amphibole exhibit pronounced Nb–Ta and Zr–Hf troughs, marked Pb peak, and enrichment in LILE coupled with HFSE depletion in the melts patterns, all of which are indicative of magma generation in a subduction-related arc setting from depleted mantle source metasomatized by slab-derived aqueous fluids. Moreover, zircon trace element compositions further support an oceanic island arc setting, displaying geochemical signatures akin to zircons from modern island arc magmas. The calculated ƒO2 values (FMQ +1 to FMQ + 3.7) and high water content of the parental magma (3.6–9 wt.%) confirm crystallization under oxidizing and hydrous conditions. The estimated pressure (~280 to ~550MPa) reflects crystallization depths from ~9 km to ~16 km within the oceanic arc crust. The age determined for the Motaghairat intrusion (715–703 Ma) for the first time in the present work provides new evidence that Neoproterozoic oceanic arc magmatism in the Mozambique Ocean continued to at least 700 Ma. Thus, the geochemical, mineralogical, and geochronological results of the present work collectively suggest that the Motaghairat layered mafic–ultramafic intrusion represents rare exposed deep ultramafic to gabbroic roots of the Neoproterozoic oceanic island arc.

Dahlquist, Juan A.; Morales Cámera, Matías M.; Moreno, Juan A.; Basei, Miguel A. S.; Santos da Cruz, Gilmara

doi: 10.1080/00206814.2025.2527817pmid: N/A

A robust U-Pb zircon dataset previously published in this journal revealed a magmatic system with protracted activity, characterized by three major crystallization events at 391 ± 1, 384 ± 1, and 379 ± 2 Ma. Based on these data, we proposed a conceptual model that suggests the existence of a deep mush reservoir, which enabled prolonged zircon antecrysts crystallization (ca. 395–384 Ma), followed by the crystallization of younger zircon (i.e. authocryst, 379 Ma) during emplacement. New Lu-Hf zircon data from the same U-Pb dated domains reveal that the parental magma was derived from a single heterogeneous source involving both subcontinental lithospheric mantle and Early Palaeozoic lower continental crust. Notably, Lu-Hf data from zircon indicate significant compositional variability in the magma, with a wide εHft ranges during the zircon crystallization events. This marked compositional diversity in εHft values are attributed to the crystallization of zircon antecrysts from isotopically distinct microdomains that formed melt pockets within the mush reservoir, accounting for the complex Hf isotopic signatures observed in magmatic zircon populations. These conditions persisted during magma ascent and shallow emplacement, where zircon autocrysts grew. Zircons that previously crystallized from compositionally distinct microdomains were juxtaposed within a single rock volume at the hand specimen scale, resulting in the presence of zircon crystals with different U – Pb ages but similar εHft values, or crystals with the same U – Pb ages but contrasting εHft values, all within the same rock sample. εHft zircon data, combined with geochronological and whole-rock chemistry evidence, support a model in which differentiation occurred mainly within the mush reservoir, with subsequent ascent and emplacement involving magmas with diverse geochemical compositions. Our findings indicate that whole-rock isotopic systems (e.g. Sm-Nd, Rb-Sr) reflect only the final integrated signal of the magmatic system, masking internal heterogeneity.

Wei, Xiaohao; Zhang, Rui; Kravchinsky, Vadim A.; Ferraro, Joseph V.; Qin, Jie; Ma, Minghao; Zhang, Dongyue; Li, Xiaojuan; Yue, Leping; Li, Jianxing; Xu, Yong; Ma, Ji; Zheng, Yanhong; Xian, Feng; Li, Yongbing; Zhang, Sophia Moxuan;

Maharani, Ni Luh Sri

doi: 10.1080/00206814.2025.2543272pmid: N/A