3 research outputs found
Variability of trace-elements and δ18O in drip water from Gruta del Rey Marcos, Guatemala; seasonal and environmental effects, and its implications for paleoclimate reconstructions
Guatemala is located at the core of one of the largest warming pools in the planet, the Western Hemisphere Warm Pool, an important source of tropical moisture to middle and high latitudes and, thus, a key area for paleoclimatic studies. This, along the karst pervasiveness in the area provides the opportunity to obtain high-resolution records of past hydroclimatic conditions using stalagmites. Despite this, the atmospheric and geochemical processes that might affect the variability of geochemical proxies in stalagmites are yet to be constrained, as no cave-monitoring in the area has been carried out previously. Here, we present a 2.5-year cave-monitoring study from Gruta del Rey Marcos, Guatemala, which allows to understand the effect of external atmospheric and environmental conditions upon the variability of δ18O, Mg/Ca, Sr/Ca, and Ba/Ca in drip water. By incorporating cave ventilation dynamics, isotopic information of local rainfall and cave-river water, we are able to understand the most relevant processes that affect the variability of the geochemical proxies in drip water, hence stalagmites. Our results suggest that two-isotopically distinct rainfall regimes, as well as tropical cyclones affecting the area contribute to the composition of the drip-water, hence the resulting stalagmites, with low δ18O (∼-6‰ VSMOW) values indicative of strong convective activity, whilst high δ18O values (−4.5 and −5‰ VSMOW), are indicative of poor convection and proportionally more significant winter-frontal rainfall. We also demonstrate that the trace-element composition of drip water is largely modulated by PCP, and thus, the variability in underlying stalagmites can be interpreted to reflect changes in karst humidity, with low E/Ca ratios (E = Mg, Sr, Ba), indicative of a wet epikarst and high E/Ca ratios indicative of a dry epikarst. Our results provide essential information for the interpretation of the δ18O and trace element variability in stalagmites, which can result in robust paleoclimatic reconstructions from Gruta del Rey Marcos and elsewhere in central America and southern Mexico
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Results of Geothermal Gradient Core Hole TCB-1, Tecuamburro Volcano Geothermal Site, Guatemala, Central America
Results of geological, volcanological, hydrogeochemical, and geophysical field studies conducted in 1988 and 1989 at the Tecuamburro volcano geothermal site in Guatemala indicated that there is a substantial shallow heat source beneath the area of youngest volcanism. To obtain information on subsurface temperatures and temperature gradients, stratigraphy, hydrothermal alteration, fracturing, and possible inflows of hydrothermal fluids, a geothermal gradient core hole (TCB-1) was drilled to 808 m low on the northern flank of the Tecuamburro volcano Complex, 300 km south of a 300-m-diameter phreatic crater, Laguna Ixpaco, dated at 2,910 years. Gases from acid-sulfate springs near Laguna Ixpaco consistently yield maximum estimated subsurface temperatures of 250--300{degrees}C. The temperature versus depth curve from TCB-1 does not show isothermal conditions and the calculated thermal gradients from 500--800 m is 230{degrees}C/km. Bottom hole temperature is 238{degrees}C. Calculated heat flow values are nearly 9 heat flow units (HFU). The integration of results from the TCB-1 gradient core hole with results from field studies provides strong evidence that the Tecuamburro area holds great promise for containing a commercial geothermal resource
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A re-evaluation of the Moyuta geothermal system, Southern Guatemala
Chemical and isotopic data from four fumarole sites combined with prefeasibility assessments obtained in the 1970s have resulted in a re-evaluation of the Moyuta geothermal system. Moyuta consists of an east-west trending complex of Quaternary andesite/dacite domes and flows cut by north-trending faults. Areas of fumaroles, acid springs, and bicarbonate-rich thermal springs flank the north and south sides of the volcanic complex. Chloride-rich thermal springs discharge along rivers at lower elevations around the Moyuta highland. The distribution of thermal features indicates that deep reservoir fluid rises convectively near the axis of volcanism. Geochemical data suggest that there are two subsystems having temperatures of about 210{degrees}C (north flank) and 170{degrees}C (south flank). Exploration wells sited near the most northerly fumarole (Azulco) achieved temperatures of {le}113{degrees}C at 1004 m depth. We suggest the fumaroles occur above hydrothermal outflow plumes confined to vertical, fault-controlled conduits. Better drilling sites occur closer to the intersections of the north trending faults and the Quaternary volcanic axis. 21 refs., 7 figs., 2 tabs