Abstract Igneous Plumbing Systems in sedimentary basins comprise a complex of interconnected intrusive bodies that lead to volcano formation, though their 3D distribution and dynamics are not fully understood. We characterized the post‐breakup igneous plumbing systems at the Santos and Campos Basins using wells and 3D high‐resolution seismic and magnetic data. Cinder cones were emplaced between the Upper Cretaceous and Paleogene, with an estimated total volume of 44 km 3 . In the Cabo Frio High, volcanoes are located beyond the Eocene continental shelf edge, suggesting a predominantly submarine paleoenvironment. We show evidence of a younger magmatic event in this region, where laccoliths are spatially associated with sills and vents intruding Eocene clinoforms. This is further supported by sill‐complexes and dykes beneath the volcanoes, and hydrothermal vents beneath and above them affecting up to the Paleogene. Altogether, these observations indicate: (a) the recurrence of existing conduits for fluidized material and (b) the key role of sills and dykes within the plumbing system. Igneous features are mostly aligned with the rift‐related faults and positive magnetic lineaments, suggesting a tectonic control over their emplacement. We propose a new conceptual model –HYREFRACT, for understanding the reheating and reactivation of ancient igneous and tectonic structures during subsequent magmatic events. It highlights the role of hydrothermal activity in fracturing overburden rocks, which has implications for reservoir permeability, fluid migration and gas release. Our findings offer insights into the morphology and connectivity of igneous plumbing systems at rifted margins that may serve as an analog for similar systems in basins worldwide.

Abstract The Changbaishan volcanic field, which includes the Tianchi and Wangtian'e volcanoes in China and the Namphothe volcano in North Korea, is one of the most complex and hazardous volcanic regions on Earth due to its tectonic setting and explosive Holocene activity. Although the magmatic structure beneath the Tianchi volcano has been widely studied, the subsurface systems beneath the Wangtian'e and Namphothe volcanoes remain unknown. Using receiver function data from a dense seismic array, we present the first high‐resolution images of crustal thickness and V p / V s structure across the Tianchi and Wangtian'e volcanic fields. stacking shows that the Tianchi volcano is underlain by a thick crust with high V p / V s , while the Wangtian'e volcano has normal crustal thickness but similarly elevated V p / V s . Common Conversion Point imaging reveals strong negative phases at depths of 5–10 km beneath both volcanoes, marking the likely tops of major crustal magma chambers. Ambient noise tomography, derived from the densest broadband data set collected in this region, also detects pronounced low‐velocity zones at similar depths. These results indicate that the two volcanoes form an interconnected magmatic system: mantle‐derived melts pool near the Moho beneath the Tianchi volcano and then migrate laterally to supply separate magma reservoirs beneath the Tianchi and Wangtian'e volcanoes. Notably, we identify partial melt beneath the Wangtian'e, a volcano long regarded as dormant or extinct, underscoring the need for continued monitoring and further geophysical studies of the entire Changbaishan volcanic complex.

Abstract Petrological and seismic constraints suggest differential sampling depth for ultrahigh pressure (UHP) metamorphic rocks exposed in different segments of the fossil subduction zone of the Western Alps. However, the mechanisms for the observed differential exhumation remain to be understood. Here, we account for the continental margin subduction within double subduction systems coupled with three‐dimensional (3‐D) geodynamic models to investigate the potential for this phenomenon. We tested two end‐member scenarios of upper‐plate motion, including Adria counterclockwise rotation and divergent motion away from the trench. Results show that both scenarios can produce a unidirectional increase in the metamorphic peak of exhumed UHP rocks along the orogen strike. Only in the simulations where the counterclockwise rotation of the upper plate acts as the primary driver of exhumation did the resulting characteristics of the deep structure fit with those observed in the Western Alps. They include the presence of an exhumed mantle wedge beneath the southern UHP domes and its absence beneath the northern UHP domes. Our results can be exported to other subduction zones where kinematic constraints suggest a component of upper‐plate rotation, such as eastern Papua New Guinea, and to older subduction zones where the kinematics is poorly assessed.

Abstract Pattern formation in geological materials is commonly described using analogies to Turing‐type reaction–diffusion systems, yet a unifying thermodynamic explanation remains elusive. Here we develop a multiscale, thermodynamically consistent framework for pattern‐forming instabilities in porous media undergoing coupled thermo–hydro–mechanical–chemical–electrical processes. By extending irreversible thermodynamics to include configurational degrees of freedom and Onsager–Casimir reciprocal couplings, we show that morphing patterns emerge as universal non‐equilibrium instabilities rather than system‐specific bifurcations. Part I establishes the theoretical foundations and stability criteria; applications are presented in Part II.

Abstract The Southern Hemisphere westerly winds and the Antarctic Circumpolar Current, both located offshore Chile, are key components of global climate due to their influence on Southern Ocean upwelling and nutrient utilization with implications for atmospheric CO 2 . In this study, the Holocene upwelling history of the Chilean continental margin is reconstructed using beryllium isotopes in the reactive phase of marine sediments collected off the coast of southern Chile. The increase in 10 Be/ 9 Be throughout the Holocene reflects the strengthening of coastal upwelling due to the southward shift of the Southern Hemisphere westerly winds, which is consistent with increased productivity along the Chilean margin. These observed changes support the idea that complete utilization of nitrate, exported from the Southern Ocean, likely acted to reduce the Southern Ocean's contribution to the increase in atmospheric CO 2 during the Holocene.

Abstract Quantifying common Pb, the non‐radiogenic Pb present in a mineral independent of in situ U decay, is essential for obtaining accurate U–Pb ages in common Pb‐bearing minerals such as apatite. However, constraining the amount and composition of common Pb, as well as the timing of its entrapment, remains a persistent challenge. Common Pb in apatites may be constrained by assuming a terrestrial Pb model and measuring 204 Pb, or by fitting a two‐component mixing line between radiogenic and common components. Here, we utilize an approach that combines in situ K‐feldspar Pb isotopes (a primary common Pb reference due to negligible radiogenic ingrowth) with apatite U–Pb and trace element data. This approach allows us to understand growth relationships between apatite and K‐feldspar, providing a better framework for geo‐thermochronological interpretations. Igneous or high‐grade metamorphic apatite indicates a shared common Pb reservoir with co‐existing K‐feldspar. In contrast, recrystallized, low‐grade metamorphic apatite records distinct common Pb compositions from K‐feldspar in the same rock. Although some ages derived from recrystallized apatite appear statistically significant (e.g., Mean Squared Weighted Deviation ∼1, p ( χ 2 ) ≥ 0.05) when anchored in Tera‐Wasserburg plots using K‐feldspar 207 Pb/ 206 Pb i , they can be geologically inaccurate as the common Pb composition of recrystallized apatite is demonstrably different to the primary magmatic reservoir recorded by K‐feldspar. Rather, unanchored ordinate intercepts in Tera‐Wasserburg plots may better capture secondary common Pb signatures for recrystallized apatite, constraining common Pb at the time of (re)growth. We highlight the advantages of assessing K‐feldspar‐constrained 207 Pb/ 206 Pb corrections using a multi‐proxy geochemical approach, thereby refining thermal histories within complex geological settings.

Abstract International Ocean Discovery Program (IODP) Site U1417, located in the Surveyor Fan (Gulf of Alaska), preserves hemipelagic sediments influenced by glacial and fluvial depositional processes from the Cordilleran Ice Sheet in the Chugach–St. Elias Mountains and Coastal Mountains. The biogenic opal content was measured for a total of 441 samples from the late Miocene to early Pleistocene intervals and its flux for hemipelagic sediments was calculated to trace the history of biogenic opal deposition. On the whole, the biogenic opal content confirms the division of the lithostratigraphic units and subunits: diatom‐bearing clay‐rich intervals versus clast‐rich terrigenous intervals. The high biogenic opal content results from the better preservation of diatom ooze, whereas the low biogenic opal content is due to diatom‐poor terrigenous sediments including diamict deposited from sedimentary gravity flows during the late Miocene. On the other hand, the biogenic opal deposition from the late Miocene to early Pleistocene might have been attributed to the degree of diatom production controlled by global climate change. The variation of biogenic opal flux at Site U1417, compared with other regions in the North Pacific, represents the global climate events such as Late Miocene Biogenic Bloom, mid‐Pliocene Warmth, and Northern Hemisphere Glaciation. Despite regional differences in oceanographic conditions, surface water productivity in the Gulf of Alaska has been attributed to the basin‐to‐basin redistribution of nutrients by global thermohaline circulation and the related Pacific Ocean ventilation. This study underlines that biogenic opal deposition at IODP Site U1417 has recorded global climate evolution since the late Miocene.

Abstract The High Arctic Large Igneous Province (HALIP) formed in the circum‐Arctic during the Cretaceous. The timing and duration of emplacement of these mafic magmas are important for understanding the climatic and environmental effects, yet many uncertainties remain. The dating methods used vary greatly between different regions. For example, the mafic intrusions in Svalbard have mainly been dated using the 40 K/ 40 Ar method, which is more sensitive to overprinting at lower temperatures. This is problematic especially in the Arctic, where the Eocene Eurekan orogeny has impacted the intrusions post‐emplacement. Meanwhile, in the Canadian Arctic, 206 Pb/ 238 U dating on zirconium minerals has been the most common method employed, which requires much higher temperatures to be reset. We present a new compilation of ages for HALIP igneous and volcanic rocks in the circum‐Arctic, derived from a thorough review and reassessment of previously reported data. This compilation applies rigorous, method‐specific criteria to evaluate the reliability of existing HALIP age determinations, ensuring traceability and applicability for future data sets. By establishing a robust framework for assessing age data, this approach enhances the reliability of geological interpretations of HALIP magmatism, and highlights, for example, the spatial migration of peak magmatic activity through time in the High Arctic. To improve our understanding of the temporal evolution of the HALIP, we also present a new 206 Pb/ 238 U baddeleyite isotopic dilution thermal ionization mass spectrometry age from Svalbard. The new weighted mean 206 Pb/ 238 U age from Svalbard, 123.3 ± 1.6 Ma, is based on six samples belonging to one large sill. This age is in perfect agreement with existing published 206 Pb/ 238 U and 40 Ar/ 39 Ar ages, and suggests magma emplacement on Svalbard between 124.7 ± 0.3 and 120.2 ± 1.9 Ma ago.

Abstract During subduction, the downgoing oceanic crust is exposed to high temperatures in the mantle wedge, causing volatile‐bearing minerals to break down and release hydrous fluids into the forearc. These fluids percolate upwards, reacting with the mantle wedge to form hydrated ultramafic lithologies, including serpentinite. To accurately track the fate and impact of water on the forearc, we develop time‐dependent models that self‐consistently capture both serpentinite ingrowth and the associated rheological weakening of the plate interface. Unlike many subduction models that investigate forearc serpentinization and prescribe plate velocities, geometries, or steady‐state conditions, our approach allows plates to evolve dynamically without predefined velocities or geometries. During subduction infancy, serpentinite accumulates rapidly. As subduction matures, serpentinite ingrowth decreases, and more serpentinite is also dragged downward by the slab. To elucidate the links between subduction dynamics and serpentinization, we consider variations in serpentinite strength and hydration state of the incoming plate. Subducting fully water‐saturated sediments yield ∼3× greater forearc serpentinite than within the moderately hydrated reference case. The water‐saturated case produces a weaker interface and, in turn, subduction zone convergence rates ∼40% higher than in an endmember case with anhydrous sediment. A lower serpentinite strength also produces higher convergence rates despite more downdragging of serpentinite from the forearc. We find that hydrous sediments not only lubricate the interface directly by weakening it, as previously suggested, but also by dehydrating and releasing water that produces weak serpentinite in the mantle wedge, with such feedback only able to be captured within fully coupled dynamic models.