cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.22227069.v1
title: Accretion and subduction mass transfer processes: Zircon SHRIMP and geochemical insights from the Carboniferous Western Series, Central Chile

description: In the region of Pichilemu (Central Chile), the exhumed roots of the Carboniferous paleo-accretionary wedge developed during subduction of an oceanic realm underneath the western Gondwana margin are exposed. We focus on the areas of Infiernillo beach and Punta de Lobos: the former representing a well-characterized transitional blueschist-facies coherent stack of metabasitic lithologies interlayered at the centimetre- to metre-scale within metasedimentary rocks and glaucophanites, whereas the latter corresponds to a massive, up to hundreds of metres thick, strained metapillow lavas edifice surrounded (not interlayered) by metasedimentary rocks. We provide new field, geochemical, Raman thermometry and zircon SHRIMP U-Th-Pb geochronology on the lithologies forming the Infiernillo-Punta de Lobos complex aiming at characterizing the sedimentary sources and the extent of mechanical mixing. Field observations suggest that the Infiernillo-Punta de Lobos complex can be considered as part of the same successions, subducted and basally accreted almost coherently at high pressure-low temperature (HP-LT) conditions. The geochemistry signal in metasedimentary rocks and maximum deposition ages point to a marked forearc source for all the metasedimentary and glaucophanite lithologies, whereas massive metapillow lavas and greenschists might represent volcanic products and oceanic roughnesses erupted near the trench when the oceanic material approached the Gondwana margin at c. 329 Ma. It is suggested that the interlayering now observed in the field is mostly the consequence of sedimentary and/or volcanic processes close to the trench environment, with minor tectonic reworking of the pre-subduction structures (e.g. lithological contacts). Our results suggest that the Punta de Lobos edifice is closely related to the subduction of large volumes of continent-derived, trench-filling sediments towards HP-LT conditions. Thus, in line with previous experimental and numerical simulations, we emphasize the potential role of oceanic roughness as stress perturbations that could contribute to the subduction of thick sedimentary sequences, and discuss their implications for seismogenesis.
DOI: 10.6084/m9.figshare.22638859.v1
title: Crustal structure of the Western Azuero Peninsula, Panama: Insights into the structure of accretionary complexes and forearc ophiolites

description: Detailed geologic mapping (639 field stations in ~700 km<sup>2</sup>) and a ~50 km-long gravity survey (142 stations) in the western Azuero Peninsula revealed two faulted and folded slivers of oceanic crust attached to the trailing edge of the Caribbean Large Igneous Plateau (CLIP). Our new data, along with published geochronology, allowed us to reconstruct the Cretaceous forearc configuration of the trailing edge of the CLIP prior to seamount collision, ophiolite accretion, and whole-margin deformation. The ophiolite in western Azuero is composed of two tectonic slivers arranged in south-verging, imbricated thrust faults that stack a ~73 Ma pillow, flow, and picritic basalt and black chert, together with a ~ 89–93 Ma and older basalt flows and capping red chert sequences. Accretion of these slivers to form a supra-subduction zone ophiolite resulted from the middle Eocene collision and accretion of Galapagos seamounts against the trailing edge of the CLIP. Accreted seamounts are arranged in a north-verging antiformal stack duplex, and below the thrust sheets. Change in kinematics after fission of the Cocos-Nazca Plate during early Miocene times prompted the propagation of the Azuero-Sona fault zone flower structure, favouring the preservation of these slivers of oceanic crust.
DOI: 10.6084/m9.figshare.23622504.v1
title: Ocean floor and Barrovian metamorphic events in the Mesozoic Peltetec ophiolitic belt (Ecuador)

description: The Peltetec ophiolitic belt, exposed along the western margin of the Cordillera Real (Ecuador), comprises tectonic slivers of metamorphosed (greenschist facies) and variably deformed metaperidotites (serpentinites), gabbros (locally cumulate), greenschist and sub-greenschist rocks. New field data, deformation and petrographic observations, whole-rock major element, mineral composition and P-T determinations of the Peltetec metaophiolite allow determining the metamorphic-geodynamic events of a section of the active western margin of Gondwana during the Mesozoic. Two metamorphic events are proposed: (i) ocean-floor metamorphism during the formation of oceanic lithosphere under low-pressure amphibolite facies conditions (M<sub>0</sub>), followed by (ii) prograde metamorphism up to the greenschist facies along an intermediate (Barrovian) P/T gradient (M<sub>1</sub>; ~315°C and ~ 3.9 kbar, ca. 23°C/km). The first metamorphic event occurred under near-static stress conditions and rocks did not suffer significant deformation. During this event, pyroxenes were replaced by hornblende while plagioclase recrystallized. The second event produced strongly recrystallized and foliated greenschist facies rocks with a peak assemblage of actinolite + chlorite + albite + epidote + titanite ± phengite. We interpreted that this assemblage developed during the closure of a back-arc basin and the emplacement of the ophiolite onto the continental margin in the late Triassic or possibly by compressive events in the Early Cretaceous and/or Late Cretaceous. Later processes are related to the regional mostly strike-slip Peltetec fault/shear zone that produced displacement and mixing of blocks, as indicated by cataclastic structure present in most of the slivers, but without differentiable metamorphic recrystallization overprint.
DOI: 10.6084/m9.figshare.17133480
title: A Late Cretaceous Adakitic intrusion from Northern Haiti: additional evidence for slab melting and implications for migration of ridge-trench-trench triple junction during the Cretaceous in the Greater Antilles

description: We present a new U-Pb zircon age and geochemical data from an intermediate calc-alkaline pluton with adakitic affinity from NW Hispaniola (Haiti). The data provide important constraints and offer new insight on the Late Cretaceous (~90 Ma) development and geological evolution of the Greater Antilles Arc (GAA). The pluton intrudes Cretaceous basalts and mafic basic tuffs of the volcanic arc domain in the Massif du Nord (northern Haiti), equivalent to the Tireo Fm (Cordillera Central) in the Dominican Republic. The calc-alkaline, low-K tonalite shows LREE enrichment, and HREE depletion and have geochemical features similar to adakites, including 67.11 wt.% SiO<sub>2</sub>, high Na<sub>2</sub>O contents (3.69 wt.%), and high Sr/Y (38.6). U-Pb SHRIMP zircon dating yielded a concordant <sup>206</sup>Pb/<sup>238</sup>U emplacement age of 88.9 ± 1.1 Ma, similar to other calc-alkaline intrusions in Hispaniola and Cuba related to the Cretaceous GAA. We link the presence of rocks with adakitic affinities in Eastern Cuba (La Corea and Sierra del Convento Mélanges), Haiti (Massif du Nord; present study), and Dominican Republic (Cordillera Central) with subduction of the Proto-Caribbean ridge and eastward (present coordinates) migration of the corresponding ridge-trench-trench triple junction since at least ~120 Ma in eastern Cuba to the mid-Cretaceous (~90 Ma) in Hispaniola. Here we show that this migration is not consistent with left-lateral oblique subduction and propose that it was not characterized by steady motion but by sudden jumps resulting from the segmentation of the proto-Caribbean ridge by transform faults. Ridge subduction and jumping triple point migration should have been active during the Late Cretaceous to early Tertiary, when the activity of the Proto-Caribbean ridge vanished.
DOI: 10.6084/m9.figshare.17285023.v1
title: The roles of partial melting of metasomatised mantle, magma mixing at continental crust level and fractionation in calc-alkaline minette genesis, SE Spain

description: Detailed textural and compositional study of calc-alkaline lamprophyres and minettes from Zeneta, SE Spain Neogene Volcanic Province (NVP) are used to unravel the magma sources and differentiation processes involved in their formation. The presence of xenocrysts of various origins indicates a hybrid nature involving mantle-derived alkaline lamproitic and continental crust-derived granitic parental magmas. A new U-Th-Pb zircon age of Zeneta minettes allows contextualizing their generation in time and space during regional lamproite magma intrusion and crustal anatexis in the NVP. Interaction and mixing of these compositionally contrasted magmas resulted in the formation of hybrid calc-alkaline lamprophyre minette. This process is reflected by the phases that crystallized from the hybrid magma, particularly phlogopite, and by the whole-rock composition of the less fractionated rocks. The calculated contribution of lamproitic and crustal-derived magma end-members in minette formation are 30–40% and 60–70%, respectively. Mixing of end-member magmas of contrasting rheological properties was possible only in a calculated thermal-window of 1025–1125°C, after cooling of intruding lamproitic magma and heating of host granitic anatectic region. The calculated thermal window fits with the estimated rheological properties of Zeneta minettes and the crystallization temperature of early minette-derived phlogopite. Furthermore, fractional crystallization was identified for the first time in the Zeneta minettes, based on the observed whole-rock line of descent from the less evolved mixed magmas through intermediate to felsic minettes and associated textural and compositional features of late crystallized phases. Polytope Vector Analysis allowed an integrated quantitative characterization of magma differentiation, including magma mixing and subsequent fractional crystallization. The identification of mixing and fractionation processes in calc-alkaline minettes genesis, which otherwise does not show spatial and temporal association in the field with granitic bodies, opens a new scenario to be considered in understanding the petrogenesis of these rocks.
DOI: 10.6084/m9.figshare.23622504
title: Ocean floor and Barrovian metamorphic events in the Mesozoic Peltetec ophiolitic belt (Ecuador)

description: The Peltetec ophiolitic belt, exposed along the western margin of the Cordillera Real (Ecuador), comprises tectonic slivers of metamorphosed (greenschist facies) and variably deformed metaperidotites (serpentinites), gabbros (locally cumulate), greenschist and sub-greenschist rocks. New field data, deformation and petrographic observations, whole-rock major element, mineral composition and P-T determinations of the Peltetec metaophiolite allow determining the metamorphic-geodynamic events of a section of the active western margin of Gondwana during the Mesozoic. Two metamorphic events are proposed: (i) ocean-floor metamorphism during the formation of oceanic lithosphere under low-pressure amphibolite facies conditions (M<sub>0</sub>), followed by (ii) prograde metamorphism up to the greenschist facies along an intermediate (Barrovian) P/T gradient (M<sub>1</sub>; ~315°C and ~ 3.9 kbar, ca. 23°C/km). The first metamorphic event occurred under near-static stress conditions and rocks did not suffer significant deformation. During this event, pyroxenes were replaced by hornblende while plagioclase recrystallized. The second event produced strongly recrystallized and foliated greenschist facies rocks with a peak assemblage of actinolite + chlorite + albite + epidote + titanite ± phengite. We interpreted that this assemblage developed during the closure of a back-arc basin and the emplacement of the ophiolite onto the continental margin in the late Triassic or possibly by compressive events in the Early Cretaceous and/or Late Cretaceous. Later processes are related to the regional mostly strike-slip Peltetec fault/shear zone that produced displacement and mixing of blocks, as indicated by cataclastic structure present in most of the slivers, but without differentiable metamorphic recrystallization overprint.
DOI: 10.6084/m9.figshare.23640932
title: Barrovian metamorphism in nominally lowermost Alpujarride Complex units: tectonic implications for the development of the orogenic wedge in the Western Mediterranean

description: The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed.
DOI: 10.6084/m9.figshare.23640932.v1
title: Barrovian metamorphism in nominally lowermost Alpujarride Complex units: tectonic implications for the development of the orogenic wedge in the Western Mediterranean

description: The sedimentary successions of the Permian-Triassic rifting related to the Alpine Tethys in the easternmost Lower Alpujarride units (Internal Betic Zone, south Spain) host shallow-intrusive basic bodies of Mesozoic age. These gabbroic bodies experienced low-grade Alpine metamorphic overprint, singularly recorded in three outcrops nearby Alicante city in southeast Spain: Callosa and Orihuela Ranges and Nueva Tabarca Island. Overall, the metabasic bodies still preserve magmatic ophitic/subophitic texture and relicts of magmatic augite and ferropargasite-ferroedenite-edenite and kaersutite. In contrast, metamorphic minerals include magnesioriebeckite, actinolite, albite, stilpnomelane, phengite, and chlorite. Major and trace element geochemical data suggest crystallization of the igneous protoliths from subalkaline (tholeiitic) to alkaline within-plate (continental) basaltic magmas slightly enriched in incompatible elements. These magmas with E-MORB geochemical affinity very likely intruded at shallow crustal levels in an extensional-synrift-geodynamic setting related to the breakoff of Pangea in the region. Pressure-Temperature (P-T) conditions estimated by average P-T method and pseudosection calculations suggest metamorphic peak at ca. 6 kbar at 340°C consistent with burial metamorphism down to ca. 18 km depth with intermediate thermal gradients of ca. 18°C/km. These conditions are different to the typical subduction-related blueschist facies conditions of the Lower Alpujarride units and suggest, instead, a collisional (Barrovian) event. This can be explained by a late-stage accretion of the studied units after the main subduction-related event, pointing to the dispersion of the corresponding Lower Alpujarride sections along the margin in different palaeogeographic positions before deformation and movement to their actual structural position. The metamorphic correlation of the studied units with the accreted passive margin of South Iberia (Subbetic zone) is also discussed.
DOI: 10.6084/m9.figshare.24006950
title: Pre-Alpine prograde evolution of the Upper Alpujarride (Betic-Rif belt) reveals a Paleotethys-related collision

description: Medium and high grade kyanite-bearing graphitic metapelites of the basement of the Torrox Unit (Upper Alpujarride, Western Mediterranean) show kyanite-andalusite-kyanite replacements and coexisting garnet types with complex compositional zoning and growth-dissolution stages. This allows inferring two clockwise <i>P-T</i> paths associated with contrasted orogenic cycles of latest Carboniferous – earliest Permian and Eocene(?)-Miocene age, respectively. Dated (306 ± 77 Ma) prograde medium grade garnet cores with relatively low to moderate Ca content indicates pre-Alpine barrovian metamorphism in the kyanite stability field (<i>ca</i>. 600°C, 0.7–0.8 GPa). This implies a prograde pressurization of the sequence followed by decompression, as inferred from andalusite replacements after kyanite. Deeper in the sequence, anatectic granitic orthogneisses contain high-grade graphitic kyanite-bearing metapelitic restitic enclaves. Dating of rutile (with inclusions of kyanite) and monazite (shielded in biotite) from the pelitic enclaves provided pre-Alpine ages (<i>ca</i>. 300 Ma) rejuvenated due to Alpine overprint. Such pressurization event is not consistent with a late Variscan stage, commonly identified with a tectonic scenario characterized by orogenic collapse and decompression at ca. 300 Ma. Instead, we propose a post-Variscan collision event related to the closure of the western Paleotethys. On the other hand, Ca-rich cores of garnet porphyroblasts in the medium-grade metapelites formed at 1.1–1.2 GPa, 500°C, implying a metamorphic gradient of ca. 11.5°C/km related to Eocene (?) subduction. Kyanite+phengite replacements after andalusite are related to this stage. Late Mg-rich Ca-poorer overgrowths in garnet porphyroblasts document increasing temperature during the first stage of decompression (down to 0.9 GPa at ca. 650°C) with increasing thermal gradient up to ca. 20°C/km. These two complete metamorphic cycles of pressurization and heating followed by decompression allow reconciling previous contradictory conclusions about the paragenetic and thermal gradient development during the Paleotethyan and Alpine cycles in different units of the Betic-Rif belt.
DOI: 10.6084/m9.figshare.17133480.v1
title: A Late Cretaceous Adakitic intrusion from Northern Haiti: additional evidence for slab melting and implications for migration of ridge-trench-trench triple junction during the Cretaceous in the Greater Antilles

description: We present a new U-Pb zircon age and geochemical data from an intermediate calc-alkaline pluton with adakitic affinity from NW Hispaniola (Haiti). The data provide important constraints and offer new insight on the Late Cretaceous (~90 Ma) development and geological evolution of the Greater Antilles Arc (GAA). The pluton intrudes Cretaceous basalts and mafic basic tuffs of the volcanic arc domain in the Massif du Nord (northern Haiti), equivalent to the Tireo Fm (Cordillera Central) in the Dominican Republic. The calc-alkaline, low-K tonalite shows LREE enrichment, and HREE depletion and have geochemical features similar to adakites, including 67.11 wt.% SiO<sub>2</sub>, high Na<sub>2</sub>O contents (3.69 wt.%), and high Sr/Y (38.6). U-Pb SHRIMP zircon dating yielded a concordant <sup>206</sup>Pb/<sup>238</sup>U emplacement age of 88.9 ± 1.1 Ma, similar to other calc-alkaline intrusions in Hispaniola and Cuba related to the Cretaceous GAA. We link the presence of rocks with adakitic affinities in Eastern Cuba (La Corea and Sierra del Convento Mélanges), Haiti (Massif du Nord; present study), and Dominican Republic (Cordillera Central) with subduction of the Proto-Caribbean ridge and eastward (present coordinates) migration of the corresponding ridge-trench-trench triple junction since at least ~120 Ma in eastern Cuba to the mid-Cretaceous (~90 Ma) in Hispaniola. Here we show that this migration is not consistent with left-lateral oblique subduction and propose that it was not characterized by steady motion but by sudden jumps resulting from the segmentation of the proto-Caribbean ridge by transform faults. Ridge subduction and jumping triple point migration should have been active during the Late Cretaceous to early Tertiary, when the activity of the Proto-Caribbean ridge vanished.
DOI: 10.6084/m9.figshare.21286834
title: Opening and closure of Cadomian peri-Gondwanan oceans: age and evolution of the Mérida Ophiolite (SW Iberia)

description: In the SW Iberian Massif, the Ossa-Morena Complex contains a stack of units of different origin and tectonothermal evolution. Individual terranes of the complex record a Cadomian history, traditionally interpreted in relation to the dynamics of a peri-Gondwanan volcanic arc. The interpretation of the Cadomian terranes is a key issue in the reconstruction of the Ediacaran margin of Gondwana in NW Africa. In the Mérida Massif, a mafic – ultramafic unit stacked between two units of continental or arc affinity is interpreted as a Cadomian ophiolite, the Mérida Ophiolite. Within it, mafic lithologies dated at <i>c</i>. 596 Ma (U-Pb in zircon) have calc-alkaline or tholeiitic affinity, indicating generation in a supra-subduction zone setting. The ophiolite shows a main event of Cadomian metamorphism (<i>c</i>. 590 Ma, U-Pb garnet dating) with a prograde P-T path and peak conditions at <i>c</i>. 700°C and 8 kbar. The mafic rocks show Nd isotopic compositions clearly different from those characteristics of the mafic rocks formed in the axial zone of the volcanic arc. Hence, the Mérida Ophiolite probably represents oceanic lithosphere of a back-arc basin, opened between the volcanic arc and the outer margin of Gondwana. Closure of the back-arc occurred during collision of the volcanic arc with the margin of Gondwana (starting at <i>c</i>. 590 Ma), which caused rapid accretion of the back-arc oceanic lithosphere beneath the arc and prograde metamorphism typical of subduction inception. The Mérida Ophiolite was finally obducted above the continental margin of Gondwana, presently preserved in gneissic unit piled beneath the ophiolite. Cadomian evolution of this peri-Gondwanan arc section continued with new tectonothermal events dated in the range 560–540 Ma that alternated with episodes of intense magmatic activity and preceded the collapse of the magmatic arc and its erosive levelling, followed by the generation of a new episode of intense magmatic activity in the arc and the unconformable deposition of the Ediacaran-Cambrian Malcocinado Formation.