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

Basement structure of the Hontomín CO2 storage site (Spain) determined by integration of microgravity and 3-D seismic data

A multidisciplinary study has been carried out in Hontomín (Spain) to determine the basement structural setting, its geometry and the geometry of the sedimentary succession of an area aimed to be the first Spanish pilot plant for CO2 storage. An integration of coincident 3-D seismic results, borehole data and unpublished microgravity data were used to reproduce the deep structure and topography of the basement and to quantify the thickness of the Triassic Keuper evaporites. The subsurface structure is characterized by a half-graben setting filled with Keuper evaporites (up to 2000m thick), forming an extensional forced fold. All data sets clearly identify two main fault systems, compartmentalizing the main structural domain into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome. © Author(s) 2016.The data sets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union through the “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer reviewe

The metamorphism and structure of the Maimón Formation and Duarte and Río Verde Complexes, Dominican Central Cordillera: implications for the structure and evolution of the primitive Caribbean Island Arc

[ES] 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.[EN] 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.Los autores agradecen a Peter Skelton y Reinaldo Rojas el haber proporcionado datos cronoestratigráficos inéditos sobre la Formación Calizas del Hatillo. G. Draper y J.F. Lewis desean dar gracias al Departamento de Exploración de la Compañía Falconbridge Dominicana S.A. por su asistencia en el trabajo en el campo. G. Draper agradece también las ayudas concedidas para las campañas de campo por el Latin American-Caribbean Center de la Universidad Internacional de Florida. Los autores agradecen también la revisión constructiva del manuscrito realizada por Marina Navidad y Ricardo Arenas, del Departamento de Petrología y Geoquímica de la Universidad Complutense de Madrid. Este trabajo ha sido financiado por el Programa SYSMIN de la Unión Europea.Peer reviewe

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-graben setting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union through the “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

Basement structure of the Hontomín CO2 Geological storage facility (Burgos, Spain): integration of microgravity & 3D seismic reflection data

The structure of the Hontomín CO2 geological storage research facility has been addressed combining 3D seismic reflection data, borehole information and microgravity data. The integrated interpretation constrains the basement structural setting geometry and that of the sedimentary succession. The study unravels the deep structure and topography of the basement and quantifies the thickness of the Triassic Keuper evaporites. We describe a half-grabensetting filled with Keuper evaporites (up to 2000 m) forming an extensional forced fold. Three set of faults are identified with two main fault systems compartmentalizing the area into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.The datasets in this work have been funded by Fundación Ciudad de la Energía (Spanish Government, www.ciuden.es) and by the European Union throughthe “European Energy Programme for Recovery” and the Compostilla OXYCFB300 project. Dr. Juan Alcalde is currently funded by NERC grant NE/M007251/1.Peer Reviewe

From the surface Topography to the Upper mantle beneath Central-Iberian-Zone. The ALCUDIA Seismic Experiments

American Geophysical Union, Fall Meeting 15-19 December, 2014, San FranciscoMulti-seismic experiments acquired across the central and southern part of the Iberian Peninsula provide a new insight into the structure and nature of the lithosphere beneath these areas. Normal incidence and wide-angle seismic reflection data acquired in the area resolve the internal architecture and constrain the distribution of the physical properties along an almost 280 km long transect that samples the major tectonic domains of the Central Iberian Zone (CIZ) and the associated suture (e.g., the Central Unit, CU). A high quality image, ~230 km long, down to 45 km depth (~15 s TWTT) is provided by the normal incidence data set. Based on the reflectivity characteristics, the image can be divided into an upper and mid-lower crust, ~13 km and ~18 km thick, respectively. The wide-angle seismic transect extended the crustal section towards the north across the Madrid Basin. This, latter data set also sample the CIZ until the CU. This is ~280 km long profile which provides very strong constraints on the distribution of physical properties (P wave and S wave velocities, Poisson's ratio) of the upper lithosphere. The PiP and PmP seismic phases constrain two discontinuities: the brittle to ductile discontinuity at ~13-19 km and the Moho boundary at ~31-35.5 km. Currently both appear to act as decoupling surfaces and are interpreted to represent levels of lithological/rheological variations. The internal structure of the Moho is further discussed taking into account the characteristics of the PmP reflections. Furthermore, low fold wide-angle P and S wave stacks reveal a marked crust-mantle transition which is most probably 5-6 km thick and relatively complex structure. The geometrical relationships of this structure with the crustal fabrics of the normal incidence image suggest that the Moho is most probably a result of the re-equilibration and/or other lithospheric processes active after the Variscan collision

Caracterización conjunta del basamento en Hontomín (España) empleando datos sísmicos y microgravimétricos

9ª Asamblea Hispano Portuguesa de Geodesia y Geofísica: Madrid 28-30 de junio 2016 / Organizado por la Comisión Española de Geodesia y Geofísica ; Secçao Portuguesa das Unios Internacionais Astronomica e Geodésica ; Universidad Complutense de MadridInstitut de Ciéncies de la Terra Jaume Almera, EspañaDepartment of Geology and Petroleum Geology, University of Aberdeen, Reino UnidoDepartamento de Geología, Universidad de Salamanca, EspañaInstituto Geológico y Minero de España, EspañaPeer reviewe

Book review

Teresa MORENO and Wes GIBBONS (eds.), The Geology of Chile. London: Geological Society, 2007