Caribbean Large Igneous Province Research Articles

Geochronological, geochemical and isotopic characterisation of the Early Cretaceous Andean margin within Ecuador: The Alao Arc

Tectonic models of the Early Cretaceous Andean margin in Ecuador are hindered by a paucity of accurate crystallisation ages of igneous rocks. The Alao Arc, situated on the western flank of the Cordillera Real in Ecuador, is mainly composed of submarine altered basalts to andesites, and the most deformed areas are frequently modified by greenschist metamorphism. To improve our knowledge of the evolution of the northern Andes prior to the accretion of the Caribbean Large Igneous Province we attempt to constrain the tectonic origin and crystallisation age of the arc's volcanic rocks, using whole-rock geochemistry and isotopic tracing, combined with 40Ar/39Ar geochronology. Major oxides and trace element abundances and Sr-Nd-Pb compositions show that the Alao Arc comprises two separate assemblages, namely, typical arc-like volcanic rocks and E-MORB-like basalts. These have been interpreted to have formed in a continental arc above thinned continental crust in an extensional setting, and the E-MORB-type basalts are considered to have formed in an intra-arc rift. As the Alao Arc's volcanic rocks are devoid of zircon and baddeleyite we attempted to date the time of their crystallisation using 40Ar/39Ar analyses of whole-rock groundmass and plagioclase. However, as the igneous rocks are modified by varying degrees of alteration with the formation of secondary K- and Ca-bearing phases, none of the ∼75 Ma to ∼16 Ma 40Ar/39Ar dates record the age of their crystallisation. The plateau and weighted mean 40Ar/39Ar date populations define peaks at ∼75–60 Ma and ∼ 45–30 Ma that coincide with previously recognised tectonic events that drove fluid circulation, modifying the Ar isotopic compositions. Based on the maximum depositional ages of intercalated sedimentary rocks, the degree of deformation, geochemical and isotopic trends of the Jurassic arc in Ecuador, and correlations with the Early Cretaceous Quebradagrande Arc of Colombia, we propose that the Alao Arc formed during ∼140–110 Ma.

Evidence for a Paleogene boninitic arc following oceanic plateau-continent collision in the Western Cordillera of Colombia

The Caicedo Tuffs is a recently mapped Paleogene volcanic arc unit in the northern Andes, which provides insight into the magmatism of northwestern South America following its collision with the Caribbean-Colombian Oceanic Plateau (CCOP) in the latest Cretaceous. New regional geological mapping, igneous petrography, whole-rock and pyroxene geochemistry, and zircon U-Pb dating are provided for the northern sector of the eastern flank of the Western Cordillera of Colombia (Antioquia). These data reveal that the Caicedo Tuffs unit is predominantly composed of primary volcaniclastic deposits (tuff to breccia) that record mafic subaqueous volcanism and limited orogenic building shortly after collision of the CCOP. The geochemistry of these deposits includes major element characteristics and immobile trace element patterns that are typical of boninites. Zircons from these igneous rocks constrain a crystallization age of ca. 57 Ma, with meso-Proterozoic to Jurassic inherited zircons most likely reflecting continental recycling by turbidites in the subduction zone. The boninitic affinity of the Caicedo Tuffs and existing regional igneous and tectonic constraints can be explained by resuming of subduction and/or sinking of an older oceanic slab along northern South America following collision of the CCOP with South America. The boninitic, primary volcaniclastic deposits of the Caicedo Tuffs are crosscut by basaltic-gabbroic sills and dykes with oceanic plateau-like geochemical affinities, which lack evidence for hydrous melting and are compositionally similar to igneous rocks of the CCOP. These intrusions are interpreted to reflect decompression melting of plume-related mantle inherited during the collision of the CCOP with South America or slab detachment. The occurrence of oceanic plateau-like intrusions in a Paleocene volcanic arc casts doubt on the origin of other oceanic plateau sequences of the Western Cordillera, which are generally attributed to the Cretaceous CCOP. The Caicedo Tuffs is a unique boninite unit of which the detailed spatiotemporal extent and petrogenesis remain to be constrained, but that can provide valuable insight into tectono-magmatic processes during oceanic plateau-continent collision.

Modeling Seismic Anisotropy Beneath the Island of Hispaniola via the Harmonic Decomposition of Receiver Functions

AbstractThe Caribbean Island of Hispaniola resulted from plate convergence that brought together distinct terranes and may include one or more active microplates. These processes may have brought seismically anisotropic materials to the island or created anisotropic structures through deformation. Our goal is to identify and model interfaces that bound seismically anisotropic media and/or dipping interfaces between isotropic layers beneath Hispaniola and assess the implications of our results for the region's tectonics. We perform harmonic decomposition of receiver function gathers for 17 broadband seismic stations deployed on the island. Our results reveal (a) a layer bounded by interfaces that produce opposite polarity on the transverse receiver functions at 25 and 41 km depth in the northern and eastern Dominican Republic that corresponds to the subducting North American oceanic lithosphere, (b) a layer at ∼8–17 km depth (also bounded by interfaces that produce opposite polarity) beneath the Cordillera Central in the central and eastern parts of the island that may indicate the crystalline, well‐differentiated lower crust of this long‐lived terrane, and (c) an interface that bounds anisotropic material at 22 km depth beneath southwestern Hispaniola. This last interface may correspond to the underthrusting Caribbean Large Igneous Province (CLIP), in which case it would mark the CLIP's upper boundary and the lower boundary is too gradual a transition to produce conversions.

Subduction initiation triggered the Caribbean large igneous province

Subduction provides the primary driving force for plate tectonics. However, the mechanisms leading to the formation of new subduction zones remain debated. An example is the Lesser Antilles Arc in the Atlantic. Previous initiation mechanisms have implied the transmission of subduction from the Pacific Ocean or the impact of a plume head. Here, we use geodynamic models to simulate the evolution of the Caribbean region during the Cretaceous, where the eastern Pacific subduction triggered the formation of a new subduction zone in the Atlantic. The simulations show how the collision of the old Caribbean plateau with the Central America margin lead to the formation of a new Atlantic subduction zone by polarity reversal. The results further show how subduction renewal on the back of the old Caribbean plateau (present-day Central America) resulted in a major mantle flow reorganization that generated a subduction-induced plume consistent with the formation of the Caribbean Large Igneous Province.

Turonian-coniacian definition of the Caribbean plate: tectonic and metamorphic record in the Median Belt, Dominican Republic

ABSTRACT Uplift and unroofing of Jurassic-Cretaceous, mantle and crust, arc- and plume-related rock units in the Median Belt of the Dominican Republic exposed basement rocks with a protracted record of tectono-thermal events delineating the evolution of the northern edge of the Caribbean plate. In this article we focus on crustal rock units in the north-eastern half of the Median Belt. First 40Ar/39Ar dating of metamorphic ferri-winchite (86.4 ± 2.5 Ma; crystallization date) and albite (82.3 ± 5.8 and 79.8 ± 1.6 Ma; cooling dates) in metabasites of boninitic photolith from the Aptian-Albian Maimón Formation in the Ozama shear zone points to a tectono-metamorphic event in the Upper Cretaceous. Beltwide, this event caused syn-metamorphic N- to NNE-directed, simple-shear dominated, mylonitic and phyllonitic deformation of the Maimón Formation at peak metamorphic conditions of 8.2 kbar and 380°C. Such conditions are consistent with subduction of a coherent portion of forearc (represented by the Maimón Formation) to depths of ~25-29 km. The tectono-metamorphic event dated here overlaps with the inception of Turonian-Coniacian SW-dipping subduction and metamorphic sole formation in a back-arc position recorded in the Moa-Baracoa ophiolite complex in neighboring Eastern Cuba. Contemporaneity between the subduction inception of forearc and back-arc portions of the Caribbean arc and the main pulse of plume activity recorded in the Caribbean Large Igneous Province (CLIP) suggests that plume activity promoted general plate instability leading to a regional-scale plate reorganization. This mantle-plume-induced plate margin reorganization was coeval with the inception of the NE-dipping subduction of the Farallón plate beneath Central America leading to the definition of the Caribbean Plate by double-verging subduction zones along its northern and southwestern margins.

Paleoenvironmental conditions over the Caribbean Large Igneous Province during the Late Cretaceous in NW of South American Margin: A sedimentological and ichnological approach

The Late Cretaceous in northwest South America was a period marked by synchronous regional geological processes (e.g., accretion of oceanic terranes, arc magmatism, sea-level fluctuations, oceanographic dynamics), related to the interaction of the Caribbean Large Igneous Province (CLIP) with the NW margin of South America. This synchroneity makes it difficult to reconstruct the complex geological evolution of this region. In Colombia, Upper Cretaceous marine sedimentary and low-grade metamorphic rocks are commonly exposed in both the Western Cordillera and the Sinú-San Jacinto Basin in the Pacific and Caribbean regions respectively. Significant deformation and structural complexity are the main limiting factors for sedimentological and paleontological studies of these deposits.Detailed sedimentological and ichnological analyses were carried out in eight sections, two in the Caribbean region and six in the Pacific region. The Caribbean sections are composed of limestones, mudrocks, siliceous and calcareous mudrocks, and cherts, associated with pelagic and hemipelagic deposits (E2.2 and G2.1 facies). The Pacific sections are characterized by two facies associations, one composed of mudrocks, limestones, as well as chert associated with pelagic and hemipelagic deposits (E2.2 and G2.1 facies) and the other of interlayered siliceous mudrocks and sandstones associated with turbiditic systems (C2 facies). Upper Cretaceous deposits in both regions are characterized by relatively low to moderate abundant and diverse trace fossils assemblages, consisting of Chondrites, Planolites, and Zoophycos in the Caribbean region and Chondrites, ?Nereites, Phycodes, Phycosiphon, Planolites, Thalassinoides, and Zoophycos in the Pacific region, assigned to the Zoophycos ichnofacies. Sedimentological and ichnological features suggest deposition in deep-marine environments characterized by pelagic, hemipelagic, and turbiditic sedimentation. Integrated with the biostratigraphical framework, this allows us to establish a regional correlation between both regions. High nutrient supply, poor oxygenation, and low hydrodynamic energy and sedimentation rates interrupted by episodic increases associated with turbiditic deposits are main paleoenvironmental factors controlling the sedimentation over the CLIP during Late Cretaceous.

Potential fields modeling for the Cayos Basin (Western Caribbean Plate): Implications in basin crustal structure

The Cayos Basin is an offshore basin located in the Colombian Caribbean Sea and forms part of the Lower Nicaraguan Rise, a geological province of the western region of the Caribbean Plate. Until now, the origin of the province is still being debated. Advanced research in the study area regarding its composition and structure, from land outcrops, petrology and geochemistry of drilled cores and dredged samples, and geophysical investigations, indicates a volcanic origin for this geological province, and a close relationship to the formation of the Caribbean Large Igneous Province. On the contrary, other studies suggest that the Lower Nicaraguan Rise may be part of the continental Chortis block. In this paper, we present and discuss alternative scenarios for the nature of the underlying crust below the sedimentary sequences in the Cayos Basin. We characterize the basin through the interpretation of magnetic and gravity anomaly grids, and 2D forward modeling, constructed based on three sections, by considering restriction seismic data from previous works. The results show that the Cayos Basin is underlain by geological bodies with high density and higher magnetization. From the gravity and magnetic forward modeling, we estimated the depth to the basement is about 2–6 km, and the Moho discontinuity to have an average of 18 km below, the Cayos Basin. Our investigation implies that, at least, the Cayos Basin is in the oceanic crust domain and shows no evidence of a continental source of the Chortis block.

Regional Geophysics of the Caribbean and Northern South America: Implications for Tectonics

AbstractThe Caribbean plate is an enclosed oceanic basin whose formation and evolution are controversial. In the most commonly accepted model, the Caribbean plate is mainly composed of the Caribbean Large Igneous Province (CLIP) and the buoyant characteristic of this oceanic plateau resisted subduction and allowed an eastward migration to its present position north of South America. In this study, we integrate a broad range of geophysical and geomorphological data to define structural elements and present‐day tectonics of the Caribbean plate and the surrounding region. We present a Bouguer gravity anomaly map and a new crustal thickness map that documents large areas of normal‐thickness oceanic crust within the Venezuela and Colombia basins of the Caribbean plate. Selected cross sections of seismicity and P‐wave anomalies from a seismic tomographic model depict the present‐day geometry of subducting oceanic plates within the Caribbean region. We observe that rather than resisting subduction, as expected for the thick crust of a buoyant large igneous province, the subduction of the Caribbean plate can be traced to a depth of 600 km beneath NW South America. This, together with the crustal thickness map, implies that a significant area of the Caribbean plate, including the subducted portion, is composed of normal‐thickness oceanic crust. As proposed by the Pacific origin model, the Caribbean plate likely migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism (CLIP).

Review of Geochronologic and Geochemical Data of the Greater Antilles Volcanic Arc and Implications for the Evolution of Oceanic Arcs

AbstractThe Greater Antilles islands of Cuba, Hispaniola, Puerto Rico and Jamaica plus the Virgin Islands host fragments of the fossil convergent margin that records Cretaceous subduction (operated for about 90 m.y.) of the American plates beneath the Caribbean plate and ensuing arc‐continent collision in Late Cretaceous‐Eocene time. The “soft” collision between the Greater Antilles Arc (GAA) and the Bahamas platform (and the margin of the Maya Block in western Cuba) preserved much of the convergent margin. This fossil geosystem represents an excellent natural laboratory for studying the formation and evolution of an intra‐oceanic convergent margin. We compiled geochronologic (664 ages) and geochemical data (more than 1,500 analyses) for GAA igneous and metamorphic rocks. The data was classified with a simple fourfold subdivision: fore‐arc mélange, fore‐arc ophiolite, magmatic arc, and retro‐arc to inspect the evolution of GAA through its entire lifespan. The onset of subduction recorded by fore‐arc units, together with the oldest magmatic arc sequence shows that the GAA started in Early Cretaceous time and ceased in Paleogene time. The arc was locally affected (retro‐arc region in Hispaniola) by the Caribbean Large Igneous Province (CLIP) in Early Cretaceous and strongly in Late Cretaceous time. Despite multiple biases in the database presented here, this work is intended to help overcome some of the obstacles and motivate systematic study of the GAA. Our results encourage exploration of offshore regions, especially in the east where the forearc is submerged. Offshore explorations are also encouraged in the south, to investigate relations with the CLIP.

Quantifying volcanism and organic carbon burial across Oceanic Anoxic Event 2

AbstractOceanic Anoxic Event 2 (ca. 94 Ma; OAE2) was one of the largest Mesozoic carbon cycle perturbations, but associated carbon emissions, primarily from the Caribbean large igneous province (LIP) and marine burial fluxes, are poorly constrained. Here, we use the carbon cycle box model LOSCAR-P to quantify the role of LIP volcanism and enhanced marine organic carbon (Corg) burial as constrained by the magnitude and shape of the positive stable carbon isotope (δ13C) excursion (CIE) in the exogenic carbon pool and atmospheric pCO2 reconstructions. In our best fit scenario, two pulses of volcanic carbon input—0.065 Pg C yr–1 over 170 k.y. and 0.075 Pg C yr–1 over 40 k.y., separated by an 80 k.y. interval with an input of 0.02 Pg C yr–1—are required to simulate observed changes in δ13C and pCO2. Reduced LIP activity and Corg burial lead to pronounced pCO2 reductions at the termination of both volcanic pulses, consistent with widespread evidence for cooling and a temporal negative trend in the global exogenic δ13C record. Finally, we show that observed leads and lags between such features in the records and simulations are explained by differences in the response time of components of the carbon cycle to volcanic forcing.

Geochronological, geochemical and isotopic characterisation of the basement of the Chocó-Panamá Block in Colombia

The Chocó-Panamá block is the land bridge that connects Central and South America and forms the trailing edge of the Caribbean Large Igneous Province (CLIP). New field observations are combined with new geochemical, isotopic and 40Ar/39Ar analyses of the mafic basement of the Chocó block within Colombia. These are integrated with new U/Pb ages of detrital zircons extracted from siliciclastic and carbonate rocks that unconformably overlie the mafic basement. The data are used to constrain the age, tectonic origin and evolution of the Chocó Block, which are used to improve tectonic models of the Caribbean Plate. The whole-rock chemical and isotopic compositions of the mafic lavas suggests they formed within an oceanic plateau, and are extremely similar to plateau units in Colombia, Ecuador, Panamá and Costa Rica. 40Ar/39Ar (groundmass) dates of the mafic basement are affected by early calcic and late potassic alteration, and none are accurate measurements of the time of crystallisation. A comparison of 40Ar(radiogenic), 39Ar(K) and 37Ar(Ca) reveals at least three argon reservoirs within the mafic groundmass, where at least two are a consequence of alteration. Our most accurate albeit imprecise estimate of the crystallisation age of the mafic basement is ≥86.0 ± 6.3 Ma, which is a plateau 40Ar/39Ar date from a groundmass aliquot which contains the lowest proportion of secondary Ar reservoirs. This age estimate is consistent with the few reliable crystallisation ages obtained for oceanic plateau rocks of the CLIP. U/Pb concordia dates of detrital zircons constrain the maximum depositional age of the overlying sedimentary rocks to ~28 Ma, supporting previous conclusions that the Chocó-Panamá block collided with South America during the Oligocene to Early Miocene. Detrital Precambrian – Triassic zircons in the older cover sequences are not present in younger sedimentary rocks due to surface uplift of the Serranía del Baudó, presumably due to collisional tectonics.

Chronology and geochemistry of the Caribbean Large Igneous Province in Jamaica

Jamaica has a complex geological history with rocks belonging to the Cretaceous Caribbean Large Igneous Province (CLIP) in the east and Cretaceous oceanic island arc rocks in the centre and west. We present a new geochemical dataset for the CLIP and correlate this dataset and previous datasets using radiolarians and planktic foraminifers to the geological timescale. The palaeontological dating indicates that two phases of plateau activity – ‘main’ phase in the late Turonian-mid Coniacian (c. 92-87 Ma) and an ‘extended’ phase in the Coniacian to mid Campanian (c. 88-75 Ma). These phases are also seen in the Beata Ridge and on the Lower Nicaragua Rise. The geochemistry indicates that both phases are typical large igneous province plateau basalts. The ‘main’ phase has slightly more depleted light rare earth elements than the extended phase, indicating mantle source heterogeneity, and a (Sm/Yb)n >1 indicates a deeper average depth of melting for the ‘main’ phase. The association of the basalts with sediments containing specific microfossil assemblages clearly demonstrates the existence of these two magmatic phases in Jamaica.

The Geochemical and Isotopic Record of Wilson Cycles in Northwestern South America: From the Iapetus to the Caribbean

Isotopic and geochemical data delineate passive margin, rift and active margin cycles in northwestern South America since ~623 Ma, spanning from the Iapetus Wilson Cycle. Ultramafic and mafic rocks record rifting associated with the formation of the Iapetus Ocean during 623–531 Ma, while the initiation of subduction of the Iapetus and Rheic oceans is recorded by continental arc plutons that formed during 499–414 Ma, with alternating compressive and extensional stages. Muscovite 40Ar/39Ar dates suggest there may have been a phase of Carboniferous metamorphism, although this remains tentative. A Passive margin was modified by active margin magmatism that started at ~294 Ma and culminated with collisional tectonics that signaled the final stages of the amalgamation of western Pangaea. Early Pangaea fragmentation included back-arc rifting during 245–216 Ma, leading to a Pacific active margin that spanned from 213–115 Ma. Trench retreat accelerated during 144–115 Ma, forming a highly attenuated continental margin prior to the collision of the Caribbean Large Igneous Province at ~75 Ma.

Seismic Discontinuities Across the North American Caribbean Plate Boundary From S‐to‐P Receiver Functions

AbstractThe evolution of the Caribbean plate has resulted in the formation of volcanic arcs, the Caribbean Large Igneous Province (CLIP) and micro‐plates across the plate boundary zones. The northern plate boundary with the North American plate has been particularly segmented with the transition from oblique subduction to oblique collision moving from east to west. However, there are few constraints on the seismic structure of the upper mantle across the plate boundary. Here we use S‐to‐P receiver functions to map seismic velocity discontinuities across the plate boundary, placing constraints on crustal and lithospheric thicknesses, as well as the structures associated with subduction and collision. We image a velocity increase with depth, consistently seen at 28–34 ± 4 km along the plate boundary, which corresponds to the Moho. A second strong velocity increase with depth is observed at depths of 64–66 ± 5 km, which is related to the presence of subducting slabs and anisotropic effects. We image a velocity decrease with depth at 95–135 ± 7 km, which reflects a lithosphere‐asthenosphere boundary that varies in depth across the plate boundary. The deepest negative discontinuity spatially maps to the CLIP. We suggest that a deep melting depth at 135 km, associated with an elevated potential mantle temperature of 1585 ± 20°C during CLIP formation, caused a depleted and dehydrated root to the base of melting, thus thickening the lithosphere.

Provenance constraints on the Cretaceous-Paleocene erosional history of the Guiana Shield as determined from the geochemistry of clay-size fraction of sediments from the Arapaima-1 well (Guyana-Suriname basin)

Recent studies have emphasized the role of the Equatorial Atlantic Ocean opening on the drainage reorganization and erosion of the West African and northeastern Brazilian cratons during the Cretaceous. However, such studies are lacking regarding the Guiana Shield. To fill this gap, we determined the provenance of sediments deposited in the Suriname-Guyana basin during the Cretaceous-Paleocene based on the total organic carbon (TOC) content, δ13CTOC, major and trace element concentrations, and Sr-Nd isotopic data of nineteen clay-size fraction samples from one industrial well (Arapaima-1). Overall, the absence of correlation between the TOC content, δ13CTOC and provenance proxies as well as the lack of Ce anomaly indicate that marine authigenesis, reducing conditions, and weathering have not markedly affected the trace element ratios (Eu/Eu*, Cr/Th, Th/Sc) and Sr-Nd isotopic compositions used as provenance proxies. Three samples (Early Cretaceous, Cenomanian and Late Campanian) have radiogenic εNd(0) values > − 2.2. The Early Cretaceous sample may have been sourced by Precambrian or Mesozoic mafic rocks of the Guiana Shield or contemporaneous basic volcanic rocks. The Cenomanian sample is likely to have been sourced by basic volcanic rocks of the Caribbean Large Igneous Province or the Takutu rift whereas the Late Campanian sample may have recorded more acid volcanism in the Takutu Rift. The other samples have an overall Guiana cratonic provenance with variable contributions of the Paleoproterozoic and Mesoproterozoic terranes and Jurassic or Precambrian mafic dykes. Increases in 87Sr/86Sr ratios and trace element ratios characteristic of more differentiated sources suggest an increasing contribution from the inner part of the Guiana Shield after the Coniacian. Because of the possible presence of active volcanism during the deposition of analyzed samples, post rift mantle upwelling under the equatorial margin is the favored mechanism to explain the increasing erosion of the Guiana Shield inner parts.

Thermal history of the southern Central Cordillera and its exhumation record in the Cenozoic deposits of the Upper Magdalena Valley, Colombia

The roughly 600 km long Central Cordillera of Colombia shows a varied tectonic, magmatic, and exhumation history, despite the reasonably homogenous appearance concerning topography, outcropping lithologies, and strike. Here we show with new geo-thermochronological data the thermal evolution of the southern Central Cordillera since the Early Jurassic. Extensive Jurassic magmatism is recorded by U–Pb crystallization ages of arc plutons intruded by dike swarms and collateral volcaniclastic flows. Inverse modeling of zircon and apatite fission-track ages from Central Cordillera reveals a long period of slow cooling since the Early Cretaceous at rates of 2–3 °C/Myr, based on best-fit t-T path solutions. The Early Cretaceous phase is recorded by the cooling of Jurassic granitoids, most likely driven by slow erosional exhumation along the western flank of the Central Cordillera related to the collision and accretion of the Quebradagrande arc against the continental margin. The Late Cretaceous rapid exhumation event caused by the ~80-70 Ma collision and accretion of the Caribbean Large Igneous Province at the western margin of South America observed in other parts of the Central Cordillera, is not detectable in our study area . During the Eocene-Oligocene (ca. 45-31 Ma), the obtained time-temperature paths are compatible with slow cooling rates between 1 and 2 °C/Myr and slow exhumation at long-term average rates of about 0.1 km/Myr. The combination of geo-thermochronological data and petrology of clastic basin sediments presented in this study indicates that the unroofing of the southern Central Cordillera crystalline basement also occurred during the Eocene-Oligocene phase of the Andean Orogeny, as widely recognized by a major unconformity. The exhumation was coeval with the reactivation of crustal structures, such as the Plata-Chusma fault, as evidenced by the syn-tectonic deposits of the Gualanday Group.

The mineral deposits of Panama: Arc metallogenesis on the trailing edge of the Caribbean large igneous province

The mineral deposits of the Panama microplate are hosted by a composite volcano-plutonic island arc of Late Cretaceous to Quaternary age developed on an oceanic plateau, the Caribbean Large Igneous Province (CLIP), on the western, trailing edge of the Caribbean Plate. Large igneous provinces are formed by gold and chalcophile element-enriched, mantle plume-related magmas, which may explain the strong metal endowment of Panama of about 32 Mt copper and >984 t gold. The progressive collision of the Panama arc with South America since the middle Eocene resulted in deformation and oroclinal bending of the arc and metallogenic belts. In western Panama, the copper-gold belts young from south to north away from the subduction zone, whereas in eastern Panama the belts young from north to south. An Early Arc of late Campanian to Eocene age (71-34 Ma) developed related to northerly subduction of the Farallon Plate. It has submarine Si-Mn-Fe exhalite deposits in the Nombre de Dios and Montijo belts with showings of Au-rich VMS Cu-Zn mineralization. The San Blas porphyry Cu-Au belt formed in eastern Panama (Rio Pito and other porphyry Cu-Au prospects), while the western continuation, offset by 200 km sinistrally to the Azuero Belt, hosts high sulphidation epithermal Au-Cu deposits (Cerro Quema and others) in porphyry lithocaps.The arc migrated to the northern Azuero-Soná belt in the middle to late Eocene with the formation of epithermal Au-Ag-Pb-Cu mineralization, and a porphyry Au prospect (Soná). A Middle Arc developed in the Oligocene to lower Miocene (31-18 Ma) related to the NE-dipping subduction of the Farallon Plate followed by the Nazca Plate. In eastern Panama, the arc formed intermediate sulphidation epithermal Au deposits in high grade breccias (Espiritu Santo de Cana mine) and carbonates (Rio Mogue prospect), and porphyry Cu mineralization (Ipeti). The eastern Panama arc shut down in the lower Miocene as a result of the change of the Nazca Plate convergence to strike slip. The Middle Arc in western Panama, on the northern side of the Central Cordillera, hosts the Petaquilla belt of porphyry Cu (the supergiant Cobre Panama porphyry Cu-Mo-Au-Ag deposit) and epithermal Au (Molejon) deposits, and probably the epithermal Au deposits of the Veraguas belt. The Later Arc of Miocene to Quaternary age (18-0 Ma) of the Central Cordillera of western Panama hosts low sulphidation epithermal Au vein and breccia-hosted deposits (Capira, Remance, Santa Rosa), high sulphidation epithermal Au deposits (Cerro Lloron, Rio Liri), and porphyry Cu deposits (the supergiant Cerro Colorado porphyry Cu-Mo-Au-Ag deposit and the Cerro Chorcha porphyry Cu-Au deposit). Uplift of the young porphyries in the western part of the belt is related to the subduction of the Cocos aseismic oceanic ridge. Deposits formed by Quaternary weathering include lateritic bauxite and iron ore in the Chiriqui-Veraguas belt; heavy mineral Fe-Ti sands in beach/marine placer deposits in the Gulf of Panama; and extensive placer Au deposits in Northern Darien, Darien, Chepo, Coclé, Veraguas, western Azuero-Soná, and many other small deposits.

Porphyry-related high-sulfidation mineralization early in Central American Arc development: Cerro Quema deposit, Azuero Peninsula, Panama

The 70.74 to 70.66 Ma age range for three molybdenite samples accompanying pyrite- and enargite-bearing assemblages effectively constrains an earliest Maastrichtian age for the high-sulfidation Au-Cu mineralization at Cerro Quema, Panama. The epithermal system was contemporaneous with emplacement of a composite dacite dome complex in a geotectonic setting transitional from mafic, primitive intraoceanic (Azuero Protoarc) to more evolved island arc magmatism (Azuero Arc), during initial construction of the Central American land bridge at the trailing edge of the Caribbean Large Igneous Province (CLIP). The molybdenite ages confirm the rapid evolution of the earliest stages of the Central American Arc, from subduction initiation at 75–73 Ma to arc maturation at 71 Ma. A porphyry connection is apparent at Cerro Quema and characterized by highly contorted, banded, and planar quartz-veinlet stockworks and sheeted zones in pyrophyllite- and sericite-bearing patchy-textured rock. These are cut by ledges of quartz, alunite, and dickite, which implies overprinting of the advanced argillic lithocap onto the underlying porphyry environment. Hydrothermal telescoping resulted from synmineralization uplift congruent with an actively emerging volcanic arc, which the Re-Os molybdenite dates accurately constrain at 71 Ma, presumably as a far-field effect of collision between the leading edge of the CLIP with parts of North and South America.

Forearc Crustal Structure of Ecuador Revealed by Gravity and Aeromagnetic Anomalies and Their Geodynamic Implications

AbstractAlong the Western Cordillera of Ecuador, fault-bounded ophiolites derived from the Late Cretaceous Caribbean Large Igneous Province (CLIP) have provided key petrotectonic indicators that outline the nature and the mechanism of continental growth in this region. However, most of the forearc basement across Western Ecuador is buried under sediments impairing its crustal structure understanding. Here, we propose a first crustal model throughout the spectral analysis of gravity and aeromagnetic data, constrained by observations made both at the surface and at the subsurface. Three main geophysical domains, within the North Andean Sliver in Western Ecuador, have been defined based on spectral analysis and augmented by 2D forward models. An outer domain, characterized by magnetic anomalies associated with mafic rocks, coincides with evidence of a split intraoceanic arc system. An inner domain is governed by long-wavelength mid to deep crust-sourced gravity and magnetic anomalies possibly evidencing the root of a paleoisland arc and the residuum of a partial melting event with subsequent associated serpentinization, the latest possibly associated with an obduction process during the middle Eocene-Oligocene. In addition, our model supports the presence of a lithospheric vertical tear fault, herein the southern suture domain, inherited from an oblique arc-continent interaction. Our interpretation also brings new insights and constraints on the early geodynamic evolution of the Ecuadorian forearc and provides evidence on the structural style and preservation potential of the forearc basement, most likely the roots of a mature island arc built within an oceanic plateau.

Cretaceous geology and tectonic assembly of Jamaica

AbstractThis paper provides new data on the Cretaceous geology together with existing data to define four terranes for the Cretaceous of Jamaica. The Northeast Blue Mountain Terrane (NEBMT) contains a shallow-water pile of Campanian basaltic and andesitic lavas interbedded with shallow-water, rudist-bearing limestones. The Southeast Blue Mountain Terrane (SEBMT) contains plume-related basalts attributed to the Caribbean Large Igneous Province (CLIP) of Turonian–Coniacian age overlain by interbedded cherts, limestones and basalts with CLIP affinity of Coniacian–Campanian age; the overlying succession is provisionally attributed to the late Campanian to Maastrichtian. The Western Blue Mountain Terrane (WBMT) contains a suite of Campanian arc rocks intruded by granodiorites which have tectonic contacts with metamorphic rocks (high pressure–low temperate blueschists, amphibolites and greenschists). The Western Jamaica Terrane (WJT) contains a suite of volcanic arc rocks in the Valanginian–Hauterivian, Barremian, Turonian, Santonian to Campanian, and Maastrichtian to Paleocene. These rocks are interbedded with thick to very thick (up to several kilometres) sedimentary sequences which occur at outcrop and in hydrocarbon exploration wells. Three major unconformities are present in the WJT, at the bases of the Crofts Synthem (earliest Campanian), Kellits Synthem (late Campanian to early Maastrichtian) and Yellow Limestone (late Paleocene to early Eocene). The NEBMT and SEBMT are separated from the WBMT and WJT by a NE–SW, left-lateral transform fault that defined the edge of the Caribbean Plate from the early(?) Cretaceous to the mid Eocene and allowed the Cuban oceanic arc and eastern Jamaican terranes to be emplaced between the Americas. Metamorphism in the WBMT indicates the existence of a northeasterly dipping subduction zone which allowed the subduction of CLIP lithosphere in the Campanian. Rudist bivalves suggest an affinity between Jamaica and the Siuna (Chortis) and Guerrero (Mexico) terranes in the Lower Cretaceous, suggesting that these arcs were close together. Subsequently, the three unconformities record interactions between the Jamaican arc segment and the Chortis Block and finally the collision with the Jamaican arc segment with the Maya Block in the Paleocene. The petroleum geology of each Cretaceous terrane is reviewed in the context of source and reservoir rocks. Possible source rocks exist in the Jurassic under northern Jamaica, the Albian to Turonian interval, which is associated with oceanic anoxic events, and the Maastrichtian, which contains thin units of organic-rich shales. Reservoirs are largely confined to limestones which preserve porosity in the body chambers of rudist bivalves and which have also been locally dolomitized and fractured (increasing both porosity and permeability). Oil-associated gas seeps present at outcrop, and oil shows of Jurassic and Cretaceous age from exploration wells indicate the existence of active petroleum systems, but not necessarily of economic hydrocarbon accumulations.