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Multi-year research on Carlin-type noble-metal mineralization has allowed the determination of deposit distribution trends, as well as the identification of several stratigraphic, geological-structural, and physicochemical conditions for the formation of the deposits. However, empirical conclusions do not fully encompass the results of modern geophysical and seismotomographic investigations. The involvement of the latter in the determination of the formation and distribution characteristics of known trends enables us to acknowledge that the Carlin world-class gold-ore province (Nevada, USA) is situated in the rear zone of the marginal-continental volcanic-plutonic belt with late Mesozoic–Cenozoic magmatism manifestations and linear belts of endogenous deposits of different formational and mineral types, which are diffusely scattered across the area of accretionary orogens. The formation of late Mesozoic–Cenozoic ore-magmatic systems in the province is predetermined by retinues of underslab and overslab asthenospheres that have been positioned as two layers beneath the continental lithosphere. The lower asthenosphere located in the mantle transition zone under the subducted Farallon plate contacted the higher asthenosphere by the upwelling of toroidal and poloidal fluid-energetic flows. Known trends of Carlin-type Au deposits were controlled by two permeable structures of deep-level geodynamics: the sublatitudinal structure of the Mendocino transform-type fault zone (Getchell and Jerritt Canyon trends), which bounds the Farallon plate in the north, and the paleo-spreading center of the East Pacific Rise of a NNW strike (Battle Mountain Eureka, Carlin, and Alligator Ridge trends).

Plate kinematic reconstructions play an essential role in our understanding of global geodynamics, but become increasingly difficult to constrain back in geological time due to the subduction of oceanic lithosphere. Here, we attempt to kinematically reconstruct the Cretaceous and older plate tectonic history of the Caribbean Plate within the Mesozoic Panthalassa (paleo-Pacific) Ocean. To this end, we present new paleomagnetic data from Jurassic and Cretaceous oceanic sedimentary and volcanic Large Igneous Province-related rocks of the Nicoya Peninsula and Murciélago Islands of northwestern Costa Rica. We use these data, in combination with constraints from marine magnetic anomalies to infer the age of the lithospheric basement, seismic tomography to locate deep-mantle plume generation zones, and general kinematic feasibility, to test different reconstruction scenarios connecting the Caribbean Plate to the Farallon Plate as restored from Pacific spreading records. Our resulting reconstruction implies that the western Caribbean subduction zone initiated around 100 Ma, in an intraoceanic setting, breaking up oceanic lithosphere of at least 70 Myr old.

The Panama Canal area is a significant part of the Panama Isthmus, where prominent volcanic fronts of eastern Central America are interrupted by a topographic low of unclear tectonic and magmatic origin. Determining why no prominent volcanic system occurs along the Canal is essential to understand the formation of the Isthmus in an area believed to have hosted one of the last inter-American straits between the Atlantic and Pacific Oceans. We provide here new geochronological and geochemical constraints from volcanic units of the Panama Canal that belong to the recently-identified Central Panama Volcanic Field. Whole rock and mineralogical geochemical compositions document a secular magmatic change from ca. 25 to 16 Ma, with a progressive change from calc-alkaline to tholeiitic and possibly alkaline/transitional geochemical affinities. The age of the youngest volcanic unit of the Canal is similar to that of the youngest documented arc volcanism in eastern Panama ca. 18 Ma. We propose based on these observations and consistency with regional geological constraints that the Canal volcanism represents a unique example of magmatic cessation along a volcanic arc. This cessation occurred shortly after the breakup of the Farallon plate ca. 23 Ma, suggesting a causal link between volcanic shutdown and transition from orthogonal to oblique subduction along Central and Eastern Panama. We suggest that this tectonic event suppressed hydrous melting in the subduction zone and led to regional magmatic waning in Central and Eastern Panama ca. 16 Ma. The pre-existence of a transisthmian fault system in Central Panama probably facilitated extraction of the last supra-subduction melts during volcanic shutdown. Our results suggest that the end of volcanism, combined with transisthmian faulting, impeded the development of high topography in the Panama Canal area. Without this unusual tectono-magmatic evolution, the occurrence of a late inter-oceanic strait in Central Panama and the construction of the Panama Canal would not have been possible.

The Vizcaino fore-arc basin accumulated approximately 4 km (∼13,000 ft) of upper Albian–middle Eocene siliciclastic marine sedimentary rocks derived from the Peninsular Ranges in Baja California. Data from eight exploratory wells document the micropaleontological content and lithological characteristics of these rocks. The strata studied represent mostly neritic–upper bathyal marine environments and overlie a basement composed of Cretaceous granitic rocks, or Aptian–Albian volcaniclastic sedimentary rocks correlative with the Alisitos Formation. We recognize four major depositional sequences within the basin that are related to the regional geology. The basal Albian–Turonian sequence 1 represents the initiation of fore-arc basin sedimentation, contains continental conglomerates that change to bathyal shales, and correlates with the lower part of the Valle Group of the Vizcaino Peninsula. Sequence 2 is Coniacian–Paleocene, includes basal conglomeratic sandstones grading into Maastrichtian bathyal shales, and usually overlies a Coniacian–Santonian unconformity. Sequence 2 is represented at the surface by the Rosario Group in northwestern Baja California and the upper part of the Valle Group in the Vizcaino Peninsula. Sequence 3 is Paleocene–middle Eocene, represents continuity of fore-arc sedimentation in neritic–upper bathyal conditions, is capped by a major unconformity, and correlates with the Sepultura and Bateque Formations to the north and south of the basin, respectively. The uppermost Miocene–Pliocene sequence 4 is composed of marine sandstone–siltstone unconformably overlying sequence 3 and is correlative with the Tortugas Formation that represents sedimentation after the end of subduction of the Farallon plate beneath the North America plate.

We present the first isotopic (noble gases and CO2) characterization of fluid inclusions coupled to Raman microspectroscopy analyses in mantle xenoliths from Central Mexico, a geodynamically complex area where the Basin and Range extension was superimposed on the Farallon subduction (terminated at 28 Ma). To characterize the isotopic signature of the Central Mexican lithospheric mantle, we focus on fluid inclusions entrapped in mantle xenoliths found in deposits of the Joya Honda maar (JH), a Quaternary monogenetic volcano belonging to the Ventura Espiritu Santo Volcanic Field (VESVF) in the state of San Luis Potosí (central Mexico). Thirteen ultramafic plagioclase-free xenoliths were selected, all exhibiting a paragenesis Ol > Opx > Cpx > > Sp, and being classified as spinel-lherzolites and harzburgites. All xenoliths bring textural evidence of interstitial glass veins bearing dendritic trails of secondary melt and fluid inclusions (composed of silicate glass ± CO2 ± Mg-Ca carbonates ± pyrite). These are related to pervasive mantle metasomatism driven by carbonate-rich silicate melt. The Ar and Ne systematics reflect mixing between MORB-like upper mantle and atmospheric fluids, the latter interpreted as reflecting a recycled air component possibly inherited from the Farallon plate subduction. The 3He/4He ratios vary between 7.13 and 7.68 Ra, within the MORB range (7–9 Ra), and the 4He/40Ar* ratios (0.4–3.11) are similarly close to the expected range of the fertile mantle (1–5). Taken together, these pieces of evidence suggest that (i) either the mantle He budget was scarcely modified by the Farallon plate subduction, and/or (ii) that any (large) crustal contribution was masked by a later metasomatism/refertilization episode, possibly during the subsequent Basin and Range extension. A silicate melt-driven metasomatism/refertilization (revealed by the association between glass veins and fluid inclusions) is consistent with calculated helium residence time for the Mexican lithospheric mantle (20 to 60 Ma) that overlaps the timing of the above geodynamic events. We propose that, after the refertilization event (e.g., over the last ~20 Ma), the lithospheric mantle has evolved in a steady-state, becoming slightly more radiogenic. We also estimated 3He fluxes (0.027–0.080 mol/g), 4He production rates (340–1000 mol/yr), and mantle CO2 fluxes (3.93 × 107 mol/yr to 1.18 × 108 mol/yr) using the helium isotopic values measured in JH mantle xenoliths. Finally, the JH xenoliths exhibit CO2/3He ratios comparable to those of the upper mantle (from 3.38 × 108 to 3.82 × 109) but more positive δ13C values (between −1.0 and − 2.7‰), supporting the involvement of a crustal carbonate component. We propose that the metasomatic silicate melts recycled a crustal carbonate component, inherited by the Farallon plate subduction.

Precise timing and constraints for magma source(s) are critical to understand the post-subduction tectonomagmatic evolution of the world's largest Cenozoic Silicic Large Igneous Province in western Mexico. We provide in-situ zircon U–Pb ages and Hf isotope compositions of rhyolitic ignimbrites exposed in the Palmarejo and Guazapares at the northwestern extremity of Sierra Madre Occidental. Four rhyolite ignimbrite samples from Palmarejo yielded zircon weighted mean U–Pb ages between 23 and 24 Ma. However, five individual analyses from one sample yielded the oldest age of 25.09 ± 0.41 Ma (MSWD = 1.7, n = 5). A rhyolitic tuff from the Guazapares district yielded older individual dates varying from 25.7 to 28.6 Ma with a main population yielding a weighted mean age of 27.31 ± 0.36 Ma. Zircon U–Pb ages suggest that the ignimbrite flare-up in southwestern Chihuahua remained restricted to the Early Middle Oligocene to Early Miocene. We suggest that the zircon U–Pb dates >24 Ma (particularly from Guazapares) are the antecrystic zircons included from the underlying older ignimbrites. The zircon U–Pb dates of 25–28 Ma are related to the culmination of syn-extensional first ignimbrite flare-up and bimodal volcanism started as early as 35 Ma. The first ignimbrite flare-up is possibly resulted from the detachment of the leading edge of the Farallon slab around 35–28 Ma. The younger age of 24–23 Ma from Palmarejo can be correlated to the second episode of ignimbrite flare-up erupted during the pervasive regional extension, normal faulting and onset of formation of metamorphic core complexes. This second flare-up is resulted by the subsequent events of break off/rollback of the Farallon plate. The positive Hf isotope composition (eHf (t) = +1.0 to +5.8) and concomitant mafic volcanism suggest partial melting of subcontinental lithospheric mantle and the overlying Laramide crust by upwelling of decompressing asthenosphere during post-Laramide regional extension. This interpretation is consistent with the successive detachments, fragmental removal and/or rollback of the leading edges of the Farallon slab beneath the western continental margin of North America. We did not find any xenocrystic zircon inheritance neither from the Laramide plutonic basement/roots of the Jurassic Guerrero terrane nor from the Proterozoic North American crust. However, zircon inheritance of Laramide age has been reported from the Guazapares district. Partial melting of Laramide basement was possibly facilitated by the heat advection and ponding of subcontinental lithospheric mantle-related magmas in the crust during the Cenozoic regional extension.

The northern Andes of Colombia comprise two non-cogenetic Paleogene arcs formed in contrasting geodynamic settings including continental and oceanic domains. New whole-rock geochemistry and isotopic constraints, together with a review of 332 geochemical, 76 isotopic and 204 geochronological data from Paleocene to Eocene volcanic and plutonic rocks exposed in central and western Colombia and Panama, are used to evaluate cause-effect relations between regional plate kinematics and the spatio-temporal distribution of the circum-Caribbean magmatic arcs. Short-lived, ~60–45 Ma arc-like magmatism in the Central Cordillera of Colombia was emplaced in a thickened continental crust due to the oblique subduction of the Caribbean oceanic plate underneath South America, as suggested by the high Sr/Y ratios. Conversely, the Panama Arc, and its poorly explored extension in the northwestern segment of the Western Cordillera of Colombia document a major phase of tholeiitic to calc-alkaline arc magmatism between ~71 Ma and ~34 Ma, mostly derived from a hydrated mantle wedge, and emplaced in an oceanic plateau crust. This arc record a major phase of magmatic activity between 40 Ma and 50 Ma that can be associated to changes in the convergence direction and subduction rates of the Farallon plate. Farther to the south, in the Pacific region of Colombia, Eocene arc-related rocks from the Timbiqui Complex show a geochemical signature that suggests a magmatic origin from melting of both a subduction-modified mantle and lower tectonically thickened crust. A possible interpretation for the Pacific and Western Colombia-Panama Arc systems, and its analogous in Ecuador, recall an Aleutian-type convergent margin in which the continental arc laterally switches to a purely oceanic system along the trailing edge of the Caribbean plate as consequence of eastward subduction of the Farallon plate.

Hotspots are generated by partial melting due to hot plumes rising within the Earth's mantle, and when tectonic plates move relative to the plume source, hotspot tracks form. Off South America, the oceanic Nazca Plate hosts a large population of hotspot tracks. Examples include seamounts formed far from the Pacific-Nazca spreading center (“off-ridge” seamounts), such as the Juan Fernandez Ridge (Juan Fernandez hotspot), the Taltal Ridge (San Felix hotspot), and the Copiapo Ridge (Caldera hotspot). These hotspot tracks are characterized by a rough and discontinuous topography. Other examples include seamounts formed near the East Pacific Rise (EPR) (“on-ridge” seamounts), such as the Nazca Ridge (Salas y Gomez hotspot) and Easter Seamount Chain (Easter hotspot), and the Iquique Ridge (Foundation hotspot). These oceanic ridges developed a relatively smooth and broad morphology. Here, we present a plate reconstruction of these six oceanic hotspot tracks since the Paleocene, providing a kinematic model of ridge-continental margin collision. For the “off-ridge” seamount group, the plate kinematic reconstruction indicates that the collision point remained quasi-stationary from 40 to 30–25 Ma. Eventually, the southward migration of the collision point of this seamount group accelerated from 23 to 15 Ma (reaching a maxima speed of 300 km/Ma along the trench). From 15 Ma to present the collision point has remained quasi-stationary. The predicted location of the subducted portion of the Taltal, Copiapo and Juan Fernandez Ridges coincides with the southward migrating (relative to South America) flat slab segment. For the “on-ridge” seamount group, the kinematic plate reconstruction indicates a continuous southward migration of the collision point from ~23 Ma, which is related to the fragmentation of the Farallon Plate. The southward migration accelerated until 15 Ma, reaching approximately 150 km/Ma. From 15 Ma to present, the southward migration has been decelerating except an increment of the migration velocity during the Chron 4 due to an increase of the convergence velocity. The migration velocity differences between the on-ridge and off-ridge hotspot tracks are mainly result from the hotspot track azimuth and the margin azimuth on the collision point. Convergence velocity varies along the trench, but it is a minor factor comparing different hotspot tracks migration velocity. Due to the EPR-plume interactions, our reconstruction suggests that the eastern Tuamotu Island Plateau formation occurred 48–27 Ma on the Easter Hotspot, which was located near to the EPR segment between the Marquesas and Austral Fracture Zones. Our model also predicts that the Iquique Ridge seamounts track is consistent with the position of the Foundation hotspot. The Foundation hotspot jumped to the Challenger (Resolution) Fracture Zone from the Farallon plate to the Pacific plate. This process triggered the cessation of the Iquique Ridge volcanic formation, and initiated volcanism at Foundation Chain in the Pacific Plate at ~25 Ma.

The breakup of continents and their subsequent drifting plays a crucial role in the Earth's periodic plate aggregation and dispersal cycles. While continental aggregation is considered the result of oceanic closure during subduction, what drives sustained divergence in the following stages remains poorly understood. In this study, thermo-mechanical numerical experiments illustrate the single contribution of subduction and coupled mantle flow to the rifting and drifting of continents. We quantify the drag exerted by subduction-induced mantle flow along the basal surface of continental plates, comparing models of lithospheric slab stagnation above the upper-lower mantle boundary with those where slabs penetrate into the lower mantle. When subduction is upper-mantle confined, divergent basal tractions localise at distances comparable to the effective upper mantle thickness (~ 500 km), causing the opening of a marginal basin. Instead, subduction of lithosphere in the lower mantle reorganises the flow into a much wider cell localising extensional stresses at greater distances from the trench (~ 3000 km). Sub-continental tractions are higher and more sustained over longer time periods in this case, and progressively increase as the slab sinks deeper. Although relatively low, basal-shear stresses when integrated over large plates, generate tension forces that may exceed the strength of the continental lithosphere, eventually leading to breakup and opening of a distal basin. The models illustrate the emergence of a similar mechanism, which results in the formation of back-arc basins above upper-mantle confined subduction, and scales to much larger distances for deeper subduction. Examples include the Atlantic Ocean formation and drifting of the South and North American plates during the Mesozoic-Cenozoic Farallon plate subduction.

The Lower Jurassic–Cenomanian successions of Mexico can be grouped into two different tectono-stratigraphic systems that were developed under the influence of two distinct geodynamic processes: 1) the Mesozoic Atlantic System of Mexico, which occupies the eastern two thirds of the country and was dominantly influenced by the break-up of Pangea and consequent opening of the Atlantic Ocean, and 2) the Mesozoic Pacific System of Mexico, which is exposed along its western margin and was controlled by the subduction of the Farallon plate beneath the Pacific margin of North America. The Mesozoic Atlantic System of Mexico can be subdivided into two tectono-stratigraphic subsystems representing the two main tectonic stages of the break-up of Pangea. The Early–Middle Jurassic rift subsystem was developed during the initial stage of lithospheric attenuation of western equatorial Pangea, which is evidenced by the opening of a number of right-lateral transtensional troughs that were opened according to the NW-SE regional extension imposed by North America-South America divergence. Rift-related troughs were progressively infilled by continental to marginal-marine deposits and, locally, by volcanic lava flows that display a geochemical signature typical of supra-subduction settings. Based on these characteristics, the rift subsystem is interpreted in this work as a hybrid tectono-stratigraphic domain that displays characteristics that are typical both of the Mesozoic Atlantic System of Mexico and Mesozoic Pacific System of Mexico, reflecting the superposition of the Atlantic and Pacific tectonic processes during the initial phase of North America-South America divergence. By late Callovian time, most of intra-continental extension in western equatorial Pangea had occurred and was followed by anticlockwise rotation of the Yucatan block to its present position and initial seafloor spreading in the Gulf of Mexico. The opening of the Gulf of Mexico promoted the incursion of marine waters in eastern Mexico and the onset of carbonate basins and platforms that make up the Late Jurassic–Cenomanian drift-and-cooling subsystem. The lack of arc-like igneous rocks in the drift-and-cooling subsystem suggests that by the late Callovian the Mesozoic Atlantic System of Mexico was developed independently of the tectonic processes related to subduction along the Pacific margin. According to our synthesis, the Mesozoic Atlantic System of Mexico represents a unique stratigraphic record that was developed, at least in part, under the combined influence of two main tectonic processes that are: 1) the divergence between North America and South America and 2) the subduction of the Farallon plate. In light of this, the Mesozoic Atlantic System of Mexico can be considered a natural laboratory to explore the evolution of complex geodynamic settings related to the interaction of plate tectonic boundaries.

Emerging over the past decade has been a new view on the genesis of, and links between, the Sierra Madre Occidental silicic large igneous province, the Comondu Group of Baja California and the Gulf of California rift. Underpinning this has been a wealth of new data from both margins of the Gulf of California including offshore sampling, and marine geophysical data, in part seeded by the NSF Margins program where the Gulf of California was a principal focus site. Previously, the Sierra Madre Occidental silicic large igneous province and Comondu Group had been widely regarded as supra - subduction volcanism with the Comondu Group in particular, defining the location of the early to mid - Miocene supra - subduction zone volcanic arc, and therefore acting as both a spatial and temporal barrier to when rifting of the Gulf of California could begin. More broadly, this continental magmatism occurring during the last phase of subduction of the Farallon Plate between the Late Eocene and the Middle Miocene, shows little to n o petrogenetic connection to the active plate boundary and is more strongly linked to the progressive thinning of the upper plate and establishment of a shallow asthenospheric mantle beneath western Mexico. A database developed for this study of 4255 ages and chemical analyses for igneous rocks from 100 to 5 Ma from across western Mexico, reveals a significant transition period between 50 and 40 Ma where relatively low - volume magmatism was established across a broad area up to 800 km wide and extended up to 1000 km in board of the paleotrench. Since 40 Ma, magma fluxes greatly increased across this broad belt and compositions were initially silicic - dominated but quickly became bimodal by ~30 Ma. The space - time pattern of crustal extension is constrained in 39 areas, for which the approximate age of extension can be established on the basis of geologic relations or thermochronology. The onset of continental extension is constrained to the Eocene when extensional basins developed across the Central Plateau and the easternmost part of the Sierra Madre Occidental, approximately 500 km in board of the paleo - plate boundary. By the end of Oligocene, crustal extension had affected a wide region (250 km width) from the eastern Sierra Madre Occidental to the site of the future Gulf of California (wide rift mode). Concomitant with this extension was: 1) a widespread invasion of the mid to upper crust by mafic magmas with lithospheric signatures (the southern cordillera orogenic basaltic andesite suite or SCORBA), and lesser erupted volumes of uncontaminated asthenosphere - derived within - plate lavas, and; 2) crustal melting producing voluminous pulses of silicic ignimbrite eruptions (the SMO SLIP) with a ferroan (dry) and transitional within - plate signature. At ~19 Ma, ortho gonal extension became focused between the western side of the SMO and eastern Baja California in a ~80 - 100 km wide belt.

The southern Central American active margin is a world-class site where past and present subduction processes have been extensively studied. Tectonic erosion/accretion and oblique/orthogonal subduction are thought to alternate in space and time along the Middle American Trench. These processes may cause various responses in the upper plate, such as uplift/subsidence, deformation, and volcanic arc migration/ shut-off. We present an updated stratigraphic framework of the Late Cretaceous– Cenozoic Sandino Forearc Basin (SFB) which provides evidence of sedimentary response to tectonic events. Since its inception, the basin was predominantly filled with deep-water volcaniclastic deposits. In contrast, shallow-water deposits appeared episodically in the basin record and are considered as tectonic event markers. The SFB stretches for about 300 km and varies in thickness from 5 km (southern part) to about 16 km (northern part). The drastic, along-basin, thickness variation appears to be the result of (1) differential tectonic evolutions and (2) differential rates of sediment supply. (1) The northern SFB did not experience major tectonic events. In contrast, the reduced thickness of the southern SFB (5 km) is the result of at least four uplift phases related to the collision/accretion of bathymetric reliefs on the incoming plate: (i) the accretion of a buoyant oceanic plateau (Nicoya Complex) during the middle Campanian; (ii) the collision of an oceanic plateau (?) during the late Danian–Selandian; (iii) the collision/accretion of seamounts during the late Eocene–early Oligocene; (iv) the collision of seamounts and ridges during the Pliocene–Holocene. (2) The northwestward thickening of the SFB may have been enhanced by high sediment supply in the Fonseca Gulf area which reflects sourcing from wide, high relief drainage basins. In contrast, sedimentary input has possibly been lower along the southern SFB, due to the proximity of the narrow, lowland isthmus of southern Central America. Moreover, two phases of strongly oblique subduction affected the margin, producing strike-slip faulting in the forearc basin: (1) prior to the Farallon Plate breakup, an Oligocene transpressional phase caused deformation and uplift of the basin depocenter, triggering shallowing-upward of the Nicaraguan Isthmus in the central and northern SFB; (2) a Pleistocene–Holocene transtensional phase drives the NW-directed motion of a forearc sliver and reactivation of the graben-bounding faults of the late Neogene Nicaraguan Depression. We discuss arguments in favour of a Pliocene development of the Nicaraguan Depression and propose that the Nicaraguan Isthmus, which is the apparent rift shoulder of the depression, represents a structure inherited from the Oligocene transpressional phase.

The subduction of the Nazca plate has specific features that impact the geophysical structure beneath Ecuador. In addition to the convexity of the trench between Peru and Ecuador, the Carnegie ridge and the Grijalva scarp are associated with strong heterogeneities in the plate that interfere with the subduction process. We have taken advantage of the large amount of manually picked P and S wave arrival times accumulated over time thanks to the national RENSIG network to perform an inversion for both event locations and seismic velocities over Ecuador within lat. 1.5 ∘ N and 5 ∘ S and long. 77 ∘ W and 82 ∘ W. After data filtering, the model presented in this article results from the inversion of 335,498 P and 111,457 S arrival times, corresponding to 25,410 events between 1988 and 2016. The intermediate depth seismicity outlines a continuous Wadati-Benioff zone in southern Ecuador that clearly defines the topography of the Farallon plate and its plunge towards the north-east at the Puyo nest, whereas in the northern part of the slab its pattern is more heterogeneous and is dominated by three nests at depths ranging between 75 km and 110 km, the Guayaquil, La Mana and Maldonado nests. The velocity model reveals a discontinuity of the Nazca plate along an axis oriented N110 ∘ E, starting in the seismogenic zone at the southern limit of the occurrence of large earthquakes. This tear is associated with an overlap of the southern Farallon part of the slab by its younger northern part. We propose that it is the result of plate buckling due to lateral compression at depth caused by the sharp bend of the trench line between Peru and Ecuador.

The Peninsular Ranges batholith (PRB) is a North American Cordillera segment with a protracted record of subduction-related magmatism (177–92 Ma). However, such a record is regionally fragmented, showing broad petrologic variations challenging to integrate into a coherent geologic evolution history. Here, we present a petrogenetic study of Cretaceous plutons in the southern PRB along the Sierra El Arco-San Francisquito transect (SW-NE) perpendicular to the paleotrench. The Middle Jurassic-Early Cretaceous (166–140 Ma) magmatism developed as an island arc with sedimentary rocks of intra-arc and oceanic marginal basins. At the Sierra El Arco, the Calmalli pluton intruded the Jurassic arc sequence. The basic to intermediate rocks of the Calmalli pluton show eSrt (average –3.6), eNdt (average +3.3), and eHft values (average +6.0) that suggest an origin from mantle-derived melts with minor contamination. These rocks display almost flat rare earth elements (REE) patterns and Eu anomalies suggesting plagioclase fractionation. East of the Calmalli pluton from the Piedra Blanca to the San Francisquito region, granodiorite and granite (100–92 Ma) are continuously exposed. The eSrt (average +3.1), eNdt (average +1.1), and eHft (average +2.6) isotopic signatures in the acid rocks suggest a mantle-derived melt genesis with increased contamination. Most granodioritic and granitic rocks display a characteristic depleted-HREE pattern without Eu anomalies, suggesting differentiation under the influence of garnet. The Jurassic-Cretaceous (166–92 Ma) magmatism displays an eSrt vs. eNdt correlation trend, indicating progressive contamination of mantle-derived magmas with a recycled crust. Sr Nd and Nd Hf isotopic mixing curves suggest the assimilation of the metasedimentary Triassic basement of NW Mexico instead of the considerably older and isotopically evolved Precambrian basement. The integration of this work with data from NW Mexico suggests a continuous magmatic activity from the Middle Jurassic to the Late Cretaceous. We consider the geochemical, isotopic, and temporal variation of the PRB indicative of natural heterogeneities along the trench axis of a long-lived arc system (crustal thickness and paleogeography) due to continuous subduction of the Farallon plate below the North American plate.

Based on chemical composition and timing of late Paleogene and Neogene igneous rocks in southern Patagonia, six igneous suites are identified and correlated with subduction processes during the approaching and subduction of active oceanic ridges. Neogene magmatism took place after a period of decreased sub-alkaline magmatism during late Paleogene (LPg Suite). Early Miocene calc-alkaline rocks mark the reactivation of magmatism after subduction acceleration (Suite 1). These rocks are located at ca. 200 km from the trench and are typical products of continental magmatic arcs, where focused metasomatism of the mantle wedge results on high-degree of partial melting (>15%) in a restricted area expressed as a narrow volcanic arc. Contrarily, transitional sub-alkaline to alkaline rocks (Suite 2) were formed during the approaching of the Chile spreading ridge and the subduction of hot oceanic lithosphere (prior to the development of a slab window), where metasomatism encompassed a broader region of the mantle wedge, resulting in lower degrees of partial melting (

Crustal and sub-crustal structure of northwestern Mexico (peninsular California) resulted from major accretion episodes occurred during the long-lived subduction of the Farallon plate beneath the North American plate, since late Jurassic time. A magnetotelluric profile across central Baja California reveals several electrical conductivity anomalies probably associated to the crustal boundaries of distinct Mezosoic terranes juxtaposed in the current peninsular crust. It is known that electrical conductivity is significantly increased by the pervasive presence of conductive minerals generated during metamorphic processes in highly sheared zones. We interpret a striking sub-horizontal conductivity anomaly reveled in the model as explained by the presence of high-salinity fluids released after dehydration of the subducted Magdalena microplate (Farallon plate?). The presence of fluids at the base of the peninsular crust may produce a zone of weakness, which supports the idea that Baja California lithosphere has not been entirely coupled to the Pacific plate. In addition, crustal thickness is estimated in our model in about 35 km beneath the western Peninsular Ranges batholith (PRB) and 20 km beneath the eastern PRB. This crustal thickness is in good agreement with independent estimations of a thinner crust in the Gulf of California margin and a thicker crust along the axial PRB.

International audience; Forearc basins have developed along accretionary and nonaccretionary convergent margins. Here, we investigate the evolution of an offshore nonaccretionary-type forearc basin that has developed along the Ecuadorian convergent margin. We used 2D-Multichannel Seismic Reflection profiles to recognize five seismic units overlying the acoustic basement. The units were dated by correlation with wells and regional stratigraphy. They recorded the structural evolution of the margin into North, Central-North and Central-South margin segments identified from Gravity Free Air Anomalies. Intersegment transition zones accommodated deformation related to the margin segmentation, contributing to the development of shelf forearc depocenters. An offshore forearc basin (subunit L1a) developed on accreted oceanic terranes during the middle-to-late Eocene. The basin was affected by normal faulting during the Oligocene to early-middle Miocene (subunit L1b). This extension stage initiated during the rifting and oblique subduction of the Farallon plate beneath the Ecuador margin. The basin underwent an early-middle Miocene uplift outlined by unconformity U1 potentially associated with the subduction of the young Nazca plate, in a less oblique plate convergence environment. During the early-Pliocene, the Central-South margin segment individualized by uplift during the formation of unconformity U2. The Manta anticline, which developed in the intersegment transition zone, accommodated the segmentation. This event is associated with the arrival of the Carnegie ridge in the subduction. The North segment individualized by uplift during the Pliocene early-Pleistocene formation of the Pedernales structural high, which may coincide with a reactivation of the Canandé fault. Synchronously, unit L3 sediment recorded the subsidence of the Central-North segment, and strike-slip tectonics in the area of the Jama-Bahía depocenter. A mosaic of middle-to-late Pleistocene unit L5 depocenters that alternate with uplifted zones along the shelf likely recorded the subduction of the topographically irregular Carnegie ridge. The study provides a remarkable example of the evolution of a non-accretionary-type forearc basin.

Geochemical variations in arc- and within-plate magmatic associations since Late Cretaceous times are analyzed and correlated with the main tectonic changes that influenced the Neuquen Basin evolution. The collision and southward migration of the Farallon-Aluk mid-ocean ridge along the Chilean trench since 80 Ma have played an important role in controlling the Late Cretaceous to Oligocene magmatic evolution of the arc and retroarc zones. The passage of this spreading center through the Chilean trench induced the development of geochemically distinct magmatic associations since Late Cretaceous to Eocene times associated with the extensional reactivation of the Cretaceous fold and thrust belt. Then, by Late Oligocene times, a major plate tectonic reorganization occurred when the Farallon plate broke apart and the resulting Nazca plate started an orthogonal subduction regime beneath the South American plate with higher convergence rates. Then extensional basins and associated magmatism developed at this time destabilizing the Paleogene fold and thrust belt and establishing a more homogeneous tholeiitic signature along the Andean axis.

At subduction zones, continental magmatic arcs are produced by differentiation processes. The Puerto Vallarta Batholith, at the Mexican Pacific margin, is the final product of the subduction of oceanic Farallon plate beneath the North American plate during the Cretaceous. Although this Cordilleran Batholith has been subject to different studies, its petrogenetic evolution remains unclear. To better constrain the magmatic processes that gave origin to the granitic rocks of the Puerto Vallarta Batholith, we combined detailed fieldwork, zircon petrochronology, and conventional thermobarometry coupled with phase equilibrium modeling. We present the crystallization and emplacement evolution, and its relationship to magmatic processes of the Puerto Vallarta Batholith. In the granitic rocks, we observed calc-alkaline and metaluminous signatures, as well as enrichment in light-rare earth elements (LREE) relative to the heavy-rare earth elements (HREE). The early crystallization stages of the Puerto Vallarta Batholith started at ~729–776 °C and ~3.5–5.3 kbar, with the last melt portion crystallized at ~675–685 °C. Fieldwork observations and Zr saturation thermometry reveal mixing of melts during the last crystallization stages. Geochemical signatures of zircons from granitic rocks suggest crystallization after minor plagioclase fractionation with likely assimilation of crustal components. Our results from geochemical whole-rock data further indicate partial melting of a heterogenous source in the mantle wedge and the differentiation of those primary melts as the principal processes that gave origin to the Puerto Vallarta Batholith. We show that the magmatic processes that originated the granitic rocks of this Cordilleran Batholith occurred in the middle crust during the Late Cretaceous. Our results provide new evidence to better constrain the origin of this magmatic system.

How deep mantle processes affected plate interactions and the dynamics of deformation on both sides of the Paleo-Pacific has been a first order scientific challenge. The ubiquitous Early Cretaceous multiphase tectonic extensional structures in eastern Eurasia (EE) show marked contrasts to the episodic compressional structures in western North America (WNA), which provides convincing arguments linking deep and shallow tectonic processes. Recent studies on Early Cretaceous tectonics in EE have shown that the continent is characterized by multiple phase of tectonic extension and weak compression, forming extensional structures in several major provinces in a vast area of ca. 3000 km × 3000 km. The peak tectonic extension occurred at 135–120 Ma, in addition to extensional episodes at pre- (160–145 Ma) and post-peak (120 Ma-) stages. Kinematic analysis reveals an identical NW-SE-oriented tectonic extension field for their formation. In addition, synextensional magmatism sourced from ancient and juvenile crust or lithospheric mantle was episodically active and peaked at ca. 160, 125 and 100–80 Ma, respectively. Particularly, a magmatic flare-up of extensional origin occurred at 125 ± 5 Ma in eastern China. In contrast, the WNA Cordillera displays a prolonged and episodic tectonic compression beginning ~170 Ma (Jurassic). Tectonic deformation involved the Nevadan, Sevier and Laramide orogenies from ca. 175 Ma, 125 Ma and 80 Ma, respectively, to form the Cordillera orogenic system. During the Nevadan orogeny intensive plate convergence from 154 to 150 Ma contributed to continental arc magmatism. The Sevier orogen is characterized by thin-skinned thrust sheets while the Laramide is dominated by shallow slab dip oceanic subduction and basement-core uplifts of Archean crust in the foreland. Significant sinistral strike-slip shearing at ~140–125 Ma is documented in the Early Cretaceous. Widespread crustal shortening and emplacement of major batholiths (magmatic flare-up) were contemporaneous with accretion of the high pressure-low temperature (blueschist) Franciscan Complex at ca. 125–100 Ma during the Sevier orogeny. The EE extensional provinces constitute part of the retreating (Paleo-) Pacific-Eurasia subduction system, while crustal shortening along the WNA was resulted from the advancing Farallon-North America subduction system. Stratified mantle convection is needed, however, when taking the tectonic evolution of the continental margins and the mid-ocean range as an integral system of the evolving globe. Shallow-mantle convection contributed to subduction of oceanic plates, which resulted in Andean-type subduction zones on both sides of the Ocean at the early stage of subduction. Possibly from 160 Ma on, eastward deep mantle flow occurred, which induced migration of the shallow mantle convection systems. As a result, the west-dipping Paleo-Pacific slabs became steepened, stagnated and subsequently folded in the mantle transition zone, while the shallow part of the east-dipping Farallon slab became flattened, and its deep part subsequently penetrated the transition zone. The resultant eastward migration of shallow mantle convection systems continuously drove the retreating subduction of the Paleo-Pacific (or Izanagi) plate, advancing subduction of the Farallon plate and eastward migration of the Paleo-Pacific-Farallon mid-ocean ridge. As a consequence, multiple phases of tectonic extension dominated the deformation of the continental interior in EE and episodic compressional tectono-magmatic activities occurred along the continental margin of WNA.

The Manihiki Plateau, a large igneous province (LIP), was emplaced in the Early Cretaceous as a single plateau together with the Ontong Java Plateau and the Hikurangi Plateau. Additional to the present Manihiki Plateau, fragments to its northeast and east have been formed. Plate kinematic reconstructions suggest the capturing of these fragments by the Farallon Plate and the Phoenix Plate, respectively. By tracing these fragments, we report a Paleocene collision of the northeastern Manihiki Plateau fragment with the northern South American craton. The northern Andes exhibit multiple terranes of LIP origin. We infer, based on geophysical, petrological, and geochemical data, that the Pinon formation consists of crustal units of the former Manihiki Plateau. An Early Cretaceous collision of the eastern Manihiki Plateau fragment is reconstructed for West Antarctica. The subduction of this fragment in the Palmer Land region can be associated with the so-called Palmer Land Event and a flattening of the subduction slab. By reconstructing the dispersal of the fragments of the Manihiki Plateau, we provide a deeper insight in the possible subduction scenarios and buildup of the accretional margins of the northern Andes and the Antarctic Peninsula.

The Laramide orogeny had a spatially variable lifespan, which we explain using a geodynamic model that incorporates onset and demise of flat-slab subduction. Laramide shortening and attendant uplift began in southeast California (USA) at ca. 90 Ma, swept to the northeast to arrive in the Black Hills of South Dakota (USA) at ca. 60 Ma, and concluded in South Dakotawithin ∼10 m.y. During subsequent slab rollback, the areal extent of Laramide deformation decreased as the eastern edge of active deformation retreated to the southwest rapidly from ca. 55 to 45 Ma and more slowly from ca. 45 to 40 Ma, with deformation ultimately ceasing in the southwestern part of the orogen at ca. 30 Ma. Geodynamic modeling of this process suggests that changes in the strength of the North America plate and densifcation of the Farallon plate played important roles in controlling the areal extent of the Laramide orogen and hence the lifespan of the orogenic event at any particular location in western North America.

Voluminous Paleogene magmatic rocks (44 to 29 Ma) are found in a retroarc position in the Northern Patagonian to Southern Central Andes (~ 39–42°S), whose origin remains controversial. Geochemical data in these Eocene to Oligocene volcanic associations are herein used to unravel their origin and understand changes in subduction parameters. Geochemical signatures indicate arc-related associations and reflect changing geodynamic boundary conditions of the Andean margin through time. In particular, Eocene magmatism (~ 44 Ma; Pilcaniyeu Belt) shows an alkaline-like signature and limited slab influence. Reported contemporaneous within-plate magmatism (~ 47–43 Ma) in an easternmost position reflects a more typical enriched source. Oligocene arc-like volcanism (~ 29 Ma; El Maitén Belt), which developed in an extensional retroarc setting, shows a higher contribution from slab-derived fluids and a calc-alkaline source. A comparison with younger arc-related magmas from the region (~ 26–20 Ma), emplaced in an intra- to retroarc position (Cura Mallín and Abanico basins), indicates a progressive increase in slab-signature, associated with a tholeiitic magma source. We propose that these compositional variations could be directly related to changes in plate configuration before and after the Farallon plate break-up and the initiation of a more orthogonal convergence typical of the present Andean-type subduction zone. Fil: Iannelli, Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Litvak, Vanesa Dafne. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Fernández Paz, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Ramos, Miguel Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Ramos, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina

New data and ideas are changing our view of conditions during the Cretaceous. Paleotopography of the continents was lower than originally thought, eliminating the ‘cold continental interior paradox’ of fossils of plants that could not tolerate freezing occurring in regions indicated by climate models to be well below freezing in winter. The controversy over the height of Cretaceous sea levels has been resolved by knowledge of the effects of passage of the subducted slab of the Farallon Plate beneath the North American crust. The cause of shorter term sea level changes of the order of 30 to 50 meters is not because of growth and decay of ice sheets, but more likely the filling and release of water from groundwater reservoirs and lakes although there may have been some ice in the Early and latest Cretaceous. Carbon dioxide was not the only significant greenhouse gas; methane contributed significantly to the warmer climate. Suggestions of very warm tropical ocean temperatures (> 40°C) have implications for the nature of plant life on land limited by Rubisco activase. The land surfaces were much wetter than has been thought, with meandering rivers and many oxbow lakes providing habitat for large dinosaurs. A major rethinking of the nature of conditions on a warmer Earth is underway, and a new suite of paleoclimate simulations for the Cretaceous is needed.

Onshore drilling by Ocean Drilling Program (ODP) Legs 150X and 174AX and offshore drilling by Integrated Ocean Drilling Program (IODP) Expedition 313 provides continuous cores and logs of seismically imaged Lower to ­Middle Miocene sequences. We input ages and paleodepths of these sequences into one-dimensional backstripping equations, progressively accounting for the effects of compaction, Airy loading, and thermal subsidence. The resulting difference between observed subsidence and theoretical thermal subsidence provide relative sea-level curves that reflect both global average sea level and non-thermal subsidence. In contrast with expectations, backstripping suggests that the relative sea-level maxima in proximal onshore sites were lower than correlative maxima on the shelf. This requires that the onshore New Jersey coastal plain has subsided relative to the shelf, which is consistent with models of relative epeirogeny due to subduction of the Farallon plate. These models predict subsidence of the coastal plain relative to the shelf. Although onshore and offshore sea-level estimates are offset by epeirogeny, the ampli­tude of million-year–scale Early to Middle Miocene sea-level changes seen at the New Jersey margin is generally 5–20 m and occasionally as great as 50 m. These events are interpreted to represent eustatic variations, because they occur on a shorter time frame than epeirogenic influences. Correction for epeiro­genic effects largely reconciles differences between onshore and offshore rela­tive sea-level estimates and suggests that backstripping provides a testable eustatic model for the Early to Middle Miocene.

The mechanism of Laramide deformation in the central Rocky Mountains remains enigmatic. It is generally agreed that the deformation resulted from low-angle subduction of the Farallon plate beneath the North American plate during the latest Cretaceous-early Eocene; however, recent studies have suggested the importance of slab removal or slab rollback in causing this deformation. Here we infer Wyoming lithosphere structure and surface deformation pattern by conducting 2-D flexural subsidence modeling in order to provide constraints on the mechanism of Laramide deformation. We assume that Wyoming lithosphere behaved as an infinite elastic plate subject to tectonic loading of mountain ranges and conduct 2-D flexural subsidence modeling to major Laramide basins to document lithospheric stiffness and mountain load height. Our results show that the stiffness of Wyoming lithosphere varied slightly in each basin during the ~30 Myr duration of the Laramide deformation and decreased from northeastern Wyoming (Te = 32–46 km) to southwestern Wyoming (Te = 6–9 km). Our results also imply that the increase of equivalent load height of major Laramide ranges accelerated during the early Eocene. We propose that the bending stresses induced by the topographic load of the Sevier fold-and-thrust belt combined with crust-mantle decoupling initiated by the overthickened Sevier hinterland and the end loads due to the low-angle subduction at the western edge of the thick Wyoming craton have caused the southwestward decrease of lithospheric stiffness in Wyoming. Moreover, we attribute the accelerated load height gain during the early Eocene to both dynamic and isostatic effects associated with slab rollback.

A new shear wave velocity model offshore Southern California is presented that images plate boundary deformation including both thickening and thinning of the crustal and mantle lithosphere at the westernmost edge of the North American continent. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) ocean bottom seismometer array, together with 65 stations of the onshore Southern California Seismic Network, is used to measure ambient noise correlation functions and Rayleigh wave dispersion curves which are inverted for 3-D shear wave velocities. The resulting velocity model defines the transition from continental lithosphere to oceanic, illuminating the complex history and deformation in the region. A transition to the present-day strike-slip regime between the Pacific and North American Plates resulted in broad deformation and capture of the now >200 km wide continental shelf. Our velocity model suggests the persistence of the uppermost mantle volcanic processes associated with East Pacific Rise spreading adjacent to the Patton Escarpment, which marks the former subduction of Farallon Plate underneath North America. The most prominent of these seismic structures is a low-velocity anomaly underlying the San Juan Seamount, suggesting ponding of magma at the base of the crust, resulting in thickening and ongoing adjustment of the lithosphere due to the localized loading. The velocity model also provides a robust framework for future earthquake location determinations and ground-shaking simulations for risk estimates.

New apatite U–Pb and multiphase 40Ar/39Ar data constrain the high to medium temperature (~ 500 °C–~ 300 °C) thermal histories of igneous and metamorphic rocks exposed in the Merida Andes of Venezuela, and new apatite and zircon fission track data constrain the ~ 500 °C–~ 60 °C thermal histories of pre-Jurassic igneous and metamorphic rocks of the adjacent Santander Massif of Colombia. Computed thermal history envelopes using apatite U–Pb dates and grain size information from an Early Palaeozoic granodiorite in the Merida Andes suggest that it cooled from > 500 °C to The generally accepted timing of amalgamation of Pangaea along the Ouachita–Marathon suture pre-dates Late Permian to Triassic cooling recorded in basement rocks of the Merida Andes by > 30 Ma, and its effect on rocks preserved in north-western South America is unknown. We interpret late Permian to Triassic cooling in the Merida Andes to be driven by exhumation. Previous studies have suggested that a short phase of shortening and anatexis is recorded at ~ 253 Ma in the Maya Block, which may have been adjacent to the basement rocks of the Merida Andes in the Late Permian. The coeval onset of exhumation in the Merida Andes may be a result of increased coupling in the magmatic arc, which was located along the western margin of Pangaea. Triassic extension is documented in the Central Cordillera of Colombia and Ecuador between ~ 240 Ma and ~ 215 Ma, although extension at this time has not been clearly identified in the Merida Andes or the Santander Massif. Permian to Triassic cooling is not recorded in the structurally isolated Caparo Block in the southern Merida Andes, suggesting that it may have constituted a distinct fault block in the Triassic. New fission track data from the Santander Massif suggest that it started exhuming at ~ 40 Ma during a period of accelerated convergence between the Nazca/Farallon Plate and the western margin of South America. Exhumation in the Santander Massif occurred diachronously since ~ 18 Ma in distinct fault blocks at rates of 0.5–1 km/Ma, and may have been driven by east–west compression as a result of the indentation of the Panama–Choco terrane to western Colombia.

Xenolith and seismic studies provide evidence for tectonic erosion and eastward displacement of lower crust-subcontinental mantle lithosphere (LC-SCML) underlying the Mojave Desert Region (i.e. southern California batholith (SCB)). Intensified traction associated with the Late Cretaceous flattening of the subducting Farallon plate, responsible for deforming the SW U.S., likely played a key role in “bulldozing” the tectonically eroded LC-SCML ∼500 km eastwards, to underneath the Colorado Plateau Transition Zone (CPTZ) and further inboard. The garnet clinopyroxenite xenoliths from two CPTZ localities, Chino Valley and Camp Creek (central Arizona), provide a rare glimpse of the material underlying the CPTZ. Thermodynamic modeling, in addition to major and trace element thermobarometry, suggests that the xenoliths experienced peak conditions of equilibration at 600-900 °C and 12-28 kbar. These peak conditions, along with the composition of the xenoliths (type “B” garnet and diopsidic clinopyroxene) strongly suggest a continental arc residue (“arclogite”), rather than a lower plate subduction (“eclogite”), origin. A bimodal zircon U-Pb age distribution with peaks at ca. 75 and 150 Ma, and a Jurassic Sm-Nd garnet age (154 ± 16 Ma, with initial eNd value of +8) overlaps eastern SCB pluton ages and suggests a consanguineous relationship. Cenozoic zircon U-Pb ages, REE geochemistry of zircon grains, and partially re-equilibrated Sm-Nd garnet ages indicate that displaced arclogite remained at elevated PT conditions (>700 °C) for 10s of Myr following its dispersal until late Oligocene entrainment in host latite. With a ∼100 Myr long thermal history overlapping that of the SCB and the CPTZ, these assemblages also contain evidence for late-stage hydration (e.g. secondary amphibole), potentially driven by de-watering of the Laramide slab. In light of these results, we suggest that the CPTZ arclogite originates from beneath the eastern half of the SCB, where it began forming in Late Jurassic time as mafic keel to continental arc magmas. The displacement and re-affixation of the arclogites further inboard during the Late Cretaceous flat slab subduction, might have contributed to the tectonic stability of the Colorado Plateau relative to adjacent geologic provinces through Laramide time and likely preconditioned the region to Cenozoic tectonism, e.g. present-day delamination beneath the plateau, high-magnitude extension and formation of metamorphic core complexes.