The Talamanca Cordillera in the Central America Arc (Costa Rica‐Panama) preserves the record of the geochemical evolution from an intraoceanic arc to a juvenile continental arc in an active subduction zone, making it a testbed to explore processes that resulted in juvenile continental crust formation and explore potential mechanisms of early continental crust generation. Here we present a comprehensive set of geochronological, geochemical, and petrological data from the Talamanca Cordillera that tracks the key turning point (12–8 Ma) from the evolution of an oceanic arc depleted in incompatible elements to a juvenile continent. Most plutonic rocks from this transition and postintrusive rocks share striking similarities with average upper continental crust and Archean tonalite, trondhjemite, and granodiorite. We complement these data with seismic studies across the arc. Seismic velocities within the Caribbean Plate (basement of the arc) show a relatively uniform lateral structure consistent with a thick mafic large igneous province. Comparisons of seismic velocity profiles in the middle and lower crust beneath the active arc and remnant Miocene arc suggest a transition toward more felsic compositions as the volcanic center migrated toward the location of the modern arc. Seismic velocities along the modern arc in Costa Rica compared with other active arcs and average continental crust suggest an intermediate composition beneath the active arc in Costa Rica closer to average crust. Our geochemical modeling and radiogenic isotopes systematics suggest that input components from melting of the subducting Galapagos hotspot tracks are required for this compositional change.
In Costa Rica the karstic phenomenon affects mainly carbonate rocks, constituting 0.85% of the country's surface, with an approximate area of 431 km 2. There are documented at least 9 episodes of carbonate deposition from the Late Cretaceous to Holocene, which include eleven stratigraphic units. These events are related to various geological-tectonic processes, changes in sea level, subsidence and changes in the sediment input. Ten karstic zones and four limestone sites have been defined: 1) North Pacific, 2) Tempisque, 3) South Zone, 4) Central Pacific, 5) Cabo Blanco and Malpaís, 6) Turrialba and Pacuare, 7) Talamanca, 8) Venado , 9) Central Valley, 10) Limón and the isolated karst areas: A) Garza, B) Cerro Huevo Frito, C)Cerro Morro and D) Playa Panama. These karstic features have morphologies which can be exo-karstic, including lapiaz, 'mogotes', karstic-towers, sinkholes and conical karst. The best known endokarstic phenomena are caves, in which it is common the development of speleothems. such as stalactites, stalagmites, columns, flowstones, draperies, calcareous pearls, etc. Serpiente Dormida (Sleeping Snake) cave is the deepest in the country, with-172 m, the longest is the Bruja-Rectangle-Tururún-Corredores system, with 3872 m in length. At least 258 caves in limestone have been registered, of which 41% have been mapped (100 caves). 88% of the caves in Costa Rica are found in karst areas of the Southern Zone (61%), Tempisque (17%) and Venado (10%), while the remaining 12% of caves are distributed in other karstic areas. These areas have special environmental and hydrogeological conditions that must be taken into account as to infrastructure development, and could also be exploited by tourism.
The Guacimal Pluton is situated in the Cordillera de Tilarán in the northwestern Costa Rica. It forms an oval-shaped body strongly elongated in the NW-SE direction. Its dimensions are ~15 × 4-6 km with an exposed surface of 60-70 km 2 . The pluton intruded basic volcanic rocks of the Aguacate Group (Miocene-Pliocene) and is surrounded by a wide thermal aureole of calc-silicate metasomatic rocks. The pluton is mainly formed of monzogranites to granodiorites, which strongly prevail over more basic types occuring scarce and relatively thin dykes and enclaves. The dominant magmatic minerals of this felsic suite are quartz, plagioclase, and K-feldspar with subordinate Mg-rich biotite, amphibole I, and magnetite. Orthopyroxene, Mn-rich ilmenite, Al-poor titanite, rutile, apatite, zircon, thorite, and chalcopyrite are accessories. Secondary minerals, which occur as fillings of miarolitic cavities and interstices, are quartz II, K-feldspar II, epidote, chlorite, actinolite, ilmenite II and Al-rich titanite II. The much less frequent mafic suite (mainly quartz diorite to quartz monzodiorite/monzogabbro) is composed of plagioclase, pargasite, actinolite, K-feldspar, quartz and magnetite, with accessory amounts of opaque minerals, epidote, chlorite, and titanite. The pluton was emplaced at a depth of c. 3 km, crystallized at temperature of c. 760-800 °C under a relatively high oxygen fugacity (1.6-2.1 log units above the NNO buffer). Increased activities of volatiles (H 2 O, F) upon cooling are indicated by the presence of highly aluminous, F-rich titanite and other hydrous silicates in miarolitic cavities. The prevailing, felsic rocks of the Guacimal Pluton are high-K calc-alkaline, whereas the mafic suite is nearly exclusively medium-K calc-alkaline in nature. Laser ablation ICP-MS dating of zircons from two granite samples yielded statistically identical U-Pb ages of 6.3 ± 0.5 and 6.0 ± 0.4 Ma, respectively. The Sr-Nd isotopic compositions are rather primitive ( 87 Sr/ 86Sr 6 = 0.70380-0.70413, ε 6 Nd ~ +7.3 to +7.9). Narrow range of these values rules out open-system processes such as magma mixing or assimilation of isotopically contrasting upper continental crust. Instead, the felsic suite is interpreted as either having crystallized from a highly fractionated melt extracted from a plagioclase-amphibole-dominated crystal mush in a putative deep crustal reservoir or a product of partial melting of older arc-related rocks, such as intermediate lavas or volcaniclastics or immature psammitic sediments rich in volcanic material. The observed variation in the felsic suite was most likely produced by low degrees of closed-system fractional crystallization of an assemblage dominated by feldspars. At least some of the rocks of the volumetrically subordinate mafic suite may represent lithologies rich in the complementary cumulates.
Abstract:The caves of the Irazú volcano (Costa Rica), became accessible after the partial collapse of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate active minerogenetic processes in volcanic cave environments. We performed a detailed mineralogical and geochemical study of speleothems in the caves Cueva los Minerales and Cueva Los Mucolitos, both located in the northwest foothills of the main crater. Mineralogical analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical characterization used Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning Electron Microscopy (SEM). In addition, measurements of environmental parameters in the caves, cave drip water and compilation of geochemical analyses of the Irazú volcanic lake (~150 m above the cave level) and fumarole analyses were conducted between 1991 and 2014. We identified forty-eight different mineral phases, mostly rare hydrated sulfates of the alunite, halotrichite, copiapite, kieserite and rozenite groups, thirteen of which are described here as cave minerals for the first time. This includes the first occurrence in cave environments of aplowite, bieberite, boyleite, dietrichite, ferricopiapite, ferrinatrite, lausenite, lishizhenite, magnesiocopiapite, marinellite, pentahydrite, szomolnokite, and wupatkiite. The presence of other new cave minerals such as tolbachite, mercallite, rhomboclase, cyanochroite, and retgersite, is likely but could not be confirmed by various mineralogical techniques. Uplifting of sulfurous gases, water seepage from the Irazú volcanic lake and hydrothermal interactions with the volcanic host rock are responsible for such extreme mineralogical diversity. These findings make the caves of the Irazú volcano a world-type-reference locality for investigations on the formation and assemblage of sulfate minerals and the biogeochemical cycle of sulfur, with potential implications for Astrobiology and Planetary science.hydrated sulfates, sulfate speleothems, volcanic caves, crater lake, cave minerogenesis Ulloa A., Gázquez F., Sanz-Arranz A., Medina J., Rull F., Calaforra J.M., Alvarado G.E., Martínez M., Avard G., de Moor J.M. and De Waele J., 2018. Extremely high diversity of sulfate minerals in caves of the Irazú Volcano (Costa Rica) related to crater lake and fumarolic activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.