Active Tectonics, Quaternary Stress Regime Evolution and Seismotectonic Faults in Southern Central Hispaniola: Implications for the Quantitative Seismic Hazard Assessment

Present-day convergence between Caribbean and North American plates is accommodated by subduction zones, major active thrusts and strike-slip faults, which are probably the source of the historical large earthquakes on Hispaniola. However, little is known of their geometric and kinematic characteristics, slip rates and seismic activity over time. This information is important to understand the active tectonics in Hispaniola, but it is also crucial to estimate the seismic hazard in the region. Here we show that a relatively constant NE-directed shortening controlled the geometry and kinematics of main active faults in southern central Hispaniola, as well as the evolution of the Quaternary stress regime. This evolution included a pre-Early Pleistocene D1 event of NE-trending compression, which gave rise to the large-scale fold and thrust structure in the Cordillera Central, Peralta Belt, Sierra Martín García and San Juan-Azua basin. This was followed by a near pure strike-slip D2 stress regime, partitioned into the N-S to NE-SW transverse Ocoa-Bonao-La Guácara and Beata Ridge fault zones, as well as subordinate structures in related sub-parallel deformation corridors. Shift to D2 strike-slip deformation was related to indentation of the Beata Ridge in southern Hispaniola from the Early to Middle Pleistocene and continues today. D2 was locally coeval by a more heterogeneous and geographically localized D3 extensional deformation. Defined seismotectonic fault zones divide the region into a set of simplified seismogenic zones as starting point for a seismic hazard modeling. Highest peak ground acceleration values computed in the Ocoa Bay establish a very high seismic hazard.The research was funded through PID2019-105625RB-C22 project of the MCIN/AEI/10.13039/501100011033 of the Spanish Government. Some works also received funding from the DR-T 1190 Project of the Banco Interamericano de Desarrollo (World Bank) and the FONDOCYT project 2015-1b3–118 of the MESCyT of the Dominican Republic Government

Metamorfismo y estructura de la Formación Maimón y los Complejos Duarte y Río Verde, Cordillera Central Dominicana: implicaciones en la estructura y la evolución del primitivo Arco Isla Caribeño

El Complejo Duarte, el Complejo Río Verde y las Formaciones de Maimón y Los Ranchos, constituyen el basamento metabasáltico pre Aptiense/Albiense del Cinturón Intermedio (CI) en la Isla de La Española. En base a las asociaciones minerales presentes en las metabasitas y las condiciones P-T estimadas mediante termobarometría, en el Complejo Río Verde es posible distinguir cuatro zonas metamórficas, desde la facies de prehnita-pumpellyta (Zona I) en la base estructural, a la de los esquistos verdes (Zonas II y III) y anfibolítica (Zona IVa), hasta la facies anfibolítica superior con clinopiroxeno (Zona IVb) a techo. Las asociaciones minerales en la Zona IVb son transicionales a la facies de las granulitas básicas de baja-P y están restringidas a las anfibolitas localizadas justo bajo el contacto tectónico con la Peridotita de Loma Caribe suprayacente. El gradiente metamórfico de campo en el Complejo Río Verde es invertido y de baja-P. Las trayectorias P-T deducidas para rocas de la Zonas IVa y IVb implican dos episodios metamórficos: (a) un calentamiento en condiciones de baja-P aproximadamente isobáricas, típico de una suela metamórfica subofiolítica; y (b) la superposición de asociaciones de media-P, siguiendo un gradiente progrado de alta-P. Estas trayectorias se interpretan como el resultado de un cabalgamiento intraoceánico durante el cierre de una cuenca de tras-arco y el inicio de la subducción de las unidades componentes del Primitivo Arco Isla Caribeño en el Aptiense/Albiense, que produce las asociaciones de mayor presión. En el sector estudiado, el Complejo Duarte se subdivide en tres zonas metamórficas, desde la parte alta de la facies de los esquistos verdes (Zona A), a la facies de las anfibolitas y anfibolitas epidóticas (Zona B), hasta la facies anfibolítica superior transicional a la facies granulítica (Zona C). El gradiente metamórfico de campo es normal y aparentemente de media-P (25-30º C/km). Los niveles estructurales más bajos del complejo están ocupados por el batolito de noritas y gabro-noritas de la Jautia, que ha desarrollado en zonas de cizalla dúctil asociaciones sincinemáticas de granulitas con Grt+Opx. La edad de 89 Ma obtenida para las intrusiones de tonalitas foliadas (U-Pb en zircones), establece una edad Cretácico Superior para esta deformación principal, consistente en un cizallamiento dúctil sinmetamórfico a gran escala. Sin embargo, la deformación es muy heterogénea en el complejo, existiendo amplios sectores metamorfizados en condiciones de un bajo esfuerzo diferencial. Por lo tanto, el metamorfismo progrado del Complejo Duarte se interpreta como el resultado del engrosamiento moderado de una corteza oceánica anormalmente potente, debido a la gran acumulación de basaltos de plateau (>30 km). Las trayectorias post-pico térmico deducidas implican la descompresión y enfriamiento del complejo (84,6±0,5 Ma; edad de enfriamiento 40Ar/39Ar de moscovitas sin-Sp), durante la formación de las fábricas deformativas y miloníticas retrógradas que constituyen la foliación principal Sp. En síntesis, las rocas metamórficas del basamento del Cinturón Intermedio registran los diferentes estadios evolutivos relacionados con la acreción-obducción del plateau de Duarte al Primitivo Arco Isla Caribeño en el Aptiense/Albiense, junto con un fragmento de litosfera oceánica. Todos estos eventos predatan la colisión final arco-continente entre el arco isla Caribeño y la plataforma carbonatada de las Bahamas durante el Cretácico Superior.The mainly metabasaltic pre-Aptian/Albian basement of the Median Belt of Hispaniola includes the Duarte Complex, the Río Verde Complex and the Maimón-Los Ranchos Formations. In base to mineral assemblages present in metabasic rocks and P-T conditions estimated from thermobarometry, the Río Verde Complex is divided into four metamorphic zones and Zone IV is further subdivided into two. The metamorphic grade increase upward in the structural sequence, from prehnite-pumpellyte facies (Zone I), through greens-chist facies (Zones II and III) and amphibolite facies (Zone IVa), to upper amphibolite facies (Zone IVb), only restricted to Cpx-bearing amphibolites just below the contact with the overlying Loma Caribe Peridotite. The metamorphic field gradient is inverse and of low-P type. The P-T paths documented for Zones IVa and IVb of the Río Verde Complex involve a two-stage prograde evolution: a first event of near isobaric heating in the low-pressure field, typical of sub-ophiolite metamorphic sole rocks and characterized by critical high-grade assemblages; and a second event marked by a medium-pressure overprint of the first-stage metamorphic assemblages following a high-P gradient. These P-T paths are interpreted to result from intra-oceanic thrusting during the closure of a back-arc basin related with the Primitive Caribbean Island Arc and the onset of subduction of arc units in the Aptian/Albian time, which formed the high-pressure metamorphic overprint. The heating and development of an inverted metamorphic gradient in the sub-ophiolite Río Verde Complex, can be genetically related with the hanginwall emplacement of the hot peridotitic slice and the conductive heat transfer downward. The studied sector of the Duarte Complex (metamorphosed oceanic plateau) is divided into three metamorphic zones. Their distribution suggest that there is a temperature increase westward and downward in the structural sequence, from the upper greenschist facies (zone A), through Ep-amphibolite and amphibolite facies (zone B), to upper amphibolite transitional to lower granulite facies (zone C). The metamorphic field gradient is normal and the mid-P type (25-30º C/km). The lowest structural levels of the complex are occupied by the gabro-norites of the La Jautía batholith, which formed in ductile shear zones Grt+Opx-bearing granulites metamorphic assemblages. The 89 Ma date obtained from foliated tonalites (U-Pb in zircons) established an Upper Cretaceous age for the main ductile shearing deformation. However, the deformation is very heterogeneous in the complex, existing regionally wide metamorphic sectors without related foliation development. Therefore, the prograde metamorphism of the Duarte Complex is interpreted to result from moderated thickening of a previously thick oceanic crust, due to the great accumulation of plateau-basalts (>30 km). The post-thermal peak P-T paths suggest the unloading and cooling of the complex, during the continuous retrograde development of deformative and mylonitic non-coaxial Sp fabrics (84,6±0,5 Ma; 40 Ar/39 Ar cooling age in syn-Sp muscovite). In summary, the metamorphic rocks of the pre-Aptian/Albian basement units of the Median Belt record different stages in the history of the acretion-obduction of the Duarte plateau with the Caribbean Primitive Island Arc. All these tectonothermal events pre-date the final arc-continent collision between the Caribbean island arc and the Bahamas platform during the Late Cretaceous

Reconstructing the Crustal Section of the Intra-Oceanic Caribbean Island Arc: Constraints From the Cumulate Layered Gabbronorites and Pyroxenites of the Rio Boba Plutonic Sequence, Northern Dominican Republic

Located in northern Dominican Republic, the Early Cretaceous Rio Boba mafic-ultramafic plutonic sequence constitutes a lower crust section of the Caribbean island arc, made up by gabbroic rocks and subordinate pyroxenite. Modal compositions, mineral chemistry, whole-rock compositions and thermobarometric calculations indicate that pyroxenites and gabbronorites represent a cumulate sequence formed by fractionation of tholeiitic magmas with initially very low H2O content in the lower crust of the arc (0.6–0.8 GPa). Melts evolved along a simplified crystallization sequence of olivine → pyroxenes → plagioclase → Fe-Ti oxides. The magmatic evolution of the Rio Boba sequence and associated supra-crustal Puerca Gorda metavolcanic rocks is multi-stage and involves the generation of magmas from melting of different sources in a supra-subduction zone setting. The first stage included the formation of a highly depleted substrate as result of decompressional melting of a refractory mantle source, represented by a cumulate sequence of LREE-depleted island arc tholeiitic (IAT) and boninitic gabbronorites and pyroxenites. The second stage involved volumetrically subordinate cumulate troctolites and gabbros, which are not penetratively deformed. The mantle source was refractory and enriched by a LILE-rich hydrous fluid derived from a subducting slab and/or overlying sediments, and possibly by a LREE-rich melt. The third stage is recorded in the upper crust of the arc by the Puerca Gorda “normal” IAT protoliths, which are derived from an N-MORB mantle source enriched with a strong subduction component. This magmatic evolution has implications for unraveling the processes responsible for subduction initiation and subsequent building of the Caribbean island arc.This research was funded through CGL2012-33669/BTE and PID2019-105625RB-C22 of the MCIN/AEI/10.13039/501100011033 projects and PRX18/00055 stay grant to the J. Escuder-Viruete of the Ministerio de Ciencia e Innovación of the Spanish Government

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Nunca como agora se conviveu com tanta invisibilidade: as imagens são hegemónicas, omnipresentes, e por isso invisíveis. Já não são dramáticas, são virais. São baratas, pervasivas, instantâneas. Aceites no seu valor micro, as imagens são monetizada, transformadas em liquidez. As imagens, cada vez mais visíveis, são por isso invisíveis. De certo modo poderemos acompanhar estas perplexidades na presente edição, onde os artistas são desafiados à visibilidade, através dos artigos aqui reunidos.info:eu-repo/semantics/publishedVersio

Subduction of fore-arc crust beneath an intra-oceanic arc: the high-P Cuaba mafic gneisess and amphibolites of the Rio San Juan Complex, Dominican Republic

The Rio San Juan metamorphic complex (RSJC) exposes a segment of a high-P accretionary prism, built during Late Cretaceous subduction below the intra-oceanic Caribbean island-arc. In this paper we present new detailed maps, tectonostratigraphy, large-scale structure, mineral chemistry, in situ trace element composition of clinopyroxene (Cpx), and bulk rock geochemical data for representative garnet-free peridotites and mafic metaigneous rocks of the Cuaba and Helechal tectonometamorphic units of the southern RSJC. The Cuaba subcomplex is composed of upper foliated amphibolites and lower garnet amphibolites, retrograded (coronitic) eclogites, and heterogeneous metagabbros metamorphosed to upper amphibolite and eclogite-facies conditions. The lenticular bodies of associated peridotites are Cpx-poor harzburgites. The underlying Helechal subcomplex is composed of Cpx-poor harzburgites, Cpx-rich harzbugites, lherzolites and rare dunites. The presented data allow us to argue that the Cuaba subcomplex: (a) represents tectonically deformed and metamorphosed crust of the Caribbean island-arc, (b) contains fragments of its supra-subduction zone mantle, and (c) includes different geochemical groups of mafic protoliths generated by varying melting degrees of diverse mantle sources. These geochemical groups include mid-Ti tholeiites (N-MORB), normal IAT and calc-alkaline rocks, low-Ti IAT, metacumulates of boninitic affinity, and HREE-depleted IAT, that collectively record a multi-stage magmatic evolution for the Caribbean island-arc, prior to the Late Cretaceous high-P metamorphism. Further, these mafic protoliths present comparable geochemical features to mafic igneous rocks of the Puerca Gorda Schists, Cacheal and Puerto Plata complexes, all of them related to the Caribbean island-arc. These relations suggest that the southern RSJC complex represents part of the subducted fore-arc of the Caribbean island-arc, which experienced initial subduction, underplating below the arc, and final exhumation in the Caribbean subduction-accretionary prism. The absence of a thick section of mafic–ultramafic cumulates also suggests delamination and/or thermomechanical erosion at the base of the Caribbean arc section during an advanced arc stage.Instituto Geológico y Minero de España, Españ

Caracterización de las fallas extensionales y de los movimientos verticales que deforman a la plataforma de coral Plio-Pleistocena del este de República Dominicana. Implicaciones para el riesgo sísmico

Congreso Internacional de Geología Aplicada (1º. 2017. Santo Domingo)Existen hoy claras evidencias de que en el este de la República Dominicana (RD) coexiste el deslizamiento sísmico por cizalla consecuencia de la colisión de Bahamas, con una menos conocida extensión activa que afecta a amplias áreas de la corteza del arco caribeño. Este estudio describe éstas últimas deformaciones y argumenta sobre un modelo tectónico integrado como premisa para la evaluación del riesgo sísmico.Instituto Geológico y Minero de España, EspañaPeer reviewe

The contribution of Manuel Fernández de Castro (1862) to the geology and mining of the Dominican Republic

[EN] The mining engineer Manuel Fernández de Castro received in 1861 a government commission to report on the geology and mining of Santo Domingo. The loss of the American colonies at the beginning of the 19th century, which had produced important incomes for the Public Treasury, motivated the interest of the rulers in the natural resources of the Antillean and Asian colonies still maintained by the Spanish crown, and especially in the coal mines. Fernández de Castro carried out his work by following ten itineraries along the eastern half of Santo Domingo, dedicating two of them to the Samaná peninsula and its coal deposits. The report was finished in 1862, and was accompanied by six maps with cartographic and mining information. Fernández de Castro produced two more memoirs, one on the geography of the country, and the other on its economic and industrial history. The commission appointed in the metropolis to evaluate its possible publication issued an unfavorable opinion: first, because some members disagreed with the geological results and, second, because of the excessive length of the texts. Its publication was rejected by the Overseas Ministry. The colony became independent in 1865 and the report fell into oblivion. In the present work, a study and evaluation of the Fernández de Castro report is carried out for the first time. The value of this work is vindicated as the first geological study of a wide territory of the Dominican Republic and the historical memory of its author as a pioneer of geological studies of the country is restored.[ES] Se presenta y analiza por vez primera el manuscrito completo del informe sobre la geología y minería de Santo Domingo, que realizó Manuel Fernández de Castro en 1861, cuando estaba destinado en la inspección de minas de Cuba. El trabajo se articuló en torno a diez recorridos por la mitad oriental de Santo Domingo. La memoria fue redactada en 1862, y se acompañó de seis mapas con informaciones geológicas y mineras. Fernández de Castro elaboró dos memorias más, una sobre la geografía del país, y otra sobre su historia económica e industrial. La comisión nombrada en la metrópoli para evaluar su posible publicación, emitió una opinión desfavorable; primero, porque algunos miembros estuvieron en desacuerdo con los resultados geológicos y, segundo, por la excesiva extensión de los textos. La publicación del informe fue denegada por el Ministerio de Ultramar. La colonia se independizó en 1865 y el estudio cayó en el olvido. Aquí se reivindica el valor de este trabajo, la primera investigación geológica de un amplio territorio de la República Dominicana y se restituye la memoria histórica de su autor, como pionero de los estudios geológicos del país.Peer reviewe

The pelona-Pico Duarte basalts Formation, Central Hispaniola: an on-land section of Late Cretaceous volcanism related to the Caribbean large-igneus province

Located in Central Hispaniola, the Pelona-Pico Duarte basalts Formation (Fm.) offers an opportunity to study the Late Cretaceous Caribbean large igneous province magmatism on land. It is composed by a ~2.5km-thick pile of massive and monotonous submarine flows of basalts, locally intruded by synvolcanic dikes and sills of dolerite. The Pelona-Pico Duarte basalts Fm. was emplaced onto Turonian-Lower Campanian island-arc volcanic and sedimentary sequences, and is overlain by Maastrichtian platformal carbonates. Two 40Ar/39Ar plateau ages indicate both extrusive and intrusive magmatic activity at least during the 79-68Ma interval (Middle Campanian to Maastrichtian), so the magmas were in part coeval with the late phases of the Caribbean large igneous province. The basalts have a restricted major-and trace-element, and isotopic, compositional variation. For a range of 47.6- 50.2wt.% SiO2, the Pelona-Pico Duarte basalts Fm. has relatively high contents in TiO2 (1.5-3.6wt.%) and Fe2O3T (10.7-13.1wt.%). On the basis of MgO contents, samples can be classified into tholeiitic basalts (20 and Zr/Nb<10) are characteristic of transitional and alkalic oceanic-island basalts. In terms of Sr-Nd isotopic composition, the samples are homogeneous and enriched relative to older Caribbean large igneous province units in Hispaniola, with (87Sr/86Sr)i ratios between 0.70330 and 0.70348 for a very restricted range of (eNd)i values between +5.0 and +5.9 (where i=70Ma). The Pelona-Pico Duarte basalts Fm. are interpreted as partial melts of a plume-related, deep enriched source, which have not been contaminated by active subduction. Mantle melt modelling indicates that both high-Mg basalts and basalts formed by mixed melts of both garnet and spinel lherzolite in variable amounts. Melts incorporated at different mantle depths, most probably in relation to the melt column processes in an upwelling plume. The Pelona-Pico Duarte basalts Fm. has significantly different values of petrogenetic tracers compared to underlying arc-related lavas, indicating a fundamental change in the mantle sources. It has geochemical affinities with the mantle domain influenced by the Late Cretaceous Caribbean plume, suggesting that enriched mantle was flowing toward the NE, to the mantle wedge region of the Caribbean island-arc, in response to rollback of the SWdirected subduction of the proto-Caribbean slab