Compilation Of Geochemical Data Research Articles

Glaciological studies in Mexico, 60 years of academic work: A summary

Glaciers have played a very important role in controlling the climate during most of the geologic history of our planet Earth. Of course, the glaciers have always been at higher latitudes (north and south), and some on high-altitude mountains. Current glaciers in Mexico are those inherited from the Last Glacial Maximum, (26000 - 19000 years before the present), increasing in size during the period of the Little Ice Age (1300 to 1850 common era), and they are unique in several ways; they are located at 19° north latitude, and they received snow precipitation from both the Pacific Ocean and the Gulf of Mexico (Atlantic Ocean). Research on glacial chronology, physical glaciology, and glacial geochemistry at Universidad Nacional Autónoma de México has provided valuable information on climate and environmental changes at different time scales, from millennial to decadal, and even annual. The first part of this work deals with the reconstruction of the glacial history in Mexico and establishing a glacial chronology from the Last Glacial Maximum to the Little Ice Age. The second part of this work focuses on monitoring recent changes (the last 60 years, 1960s to 2023) of the glacier extent on Iztaccíhuatl, Popocatépetl, and Citlaltépetl (the three highest mountains in Mexico), as well as having an updated inventory of all the glaciers at those mountains. Changes in glacier extent and thickness of ice are directly related to the increase in air temperature, variation in precipitation patterns, and glacier dynamics on some of the last glaciers of the northern tropics. The third part or this work focuses on a compilation of geochemical data from 17 years (from 2006 to 2013) of sampling ice (shallow ice cores) and snow at Iztaccíhuatl and Citlaltépetl glaciers. This database has the potential for providing interesting and useful information on natural and anthropogenic-induced changes related to the occurrence of heavy metals in tropical glaciers in the northern hemisphere of North America. Black carbon concentrations analyzed in snow and glacier ice, and preliminary data on stable isotopes of Zn, also add information on natural vs. anthropogenic sources of heavy metals in central Mexico.

The Influence of Ridge Subduction on the Geochemistry of Vanuatu Arc Magmas

AbstractThe effects of buoyant ridge subduction have been researched for decades. However, it remains unclear how this process influences magma chemistry. Here we use a compilation of geochemical data, well‐established geochemical proxies (i.e., Ba/Nb, Th/Nb) and mantle redox modeling (i.e., V/Sc, Cu) to propose that the subduction of a ridge underneath the central portion of the Vanuatu arc causes shallow‐angle subduction and the development of a slab tear. We suggest that the shallow slab pinches out the asthenospheric mantle and bulldozes ancient metasomatized lithospheric mantle from the forearc toward the main‐arc. Slab‐fluxed melting of this bulldozed material could account for the along‐arc 87Sr/86Sr‐143Nd/144Nd variations of the Vanuatu magmas. The influx of hot sub‐slab material into the Vanuatu arc mantle wedge through a slab tear produces magmatism within the forearc. Modeling of V/Sc and Cu systematics suggest that the mantle source of the forearc magmas has a higher fO2 and Cu content than the source of the main‐arc and rear‐arc samples. The main‐arc and rear‐arc mantles were metasomatized by both slab‐derived fluids and melts. Whereas release of high Cu‐SO2 slab‐derived fluids caused oxidation and Cu enrichment of the forearc mantle. These systematics indicate a decrease in the fO2 of slab fluxes with increasing depth‐to‐slab and distance‐from‐trench. Our findings highlight the role of ridge subduction in controlling the along‐arc and across‐arc variations in the chemistry of Vanuatu arc magmas. This updated geodynamic model, based on geochemistry, is consistent with recent geophysical constraints and 3D numerical modeling.

Structural, lithological, and geodynamic controls on geothermal activity in the Menderes geothermal Province (Western Anatolia, Turkey)

Western Turkey belongs to the regions with the highest geothermal potential in the world, resulting in significant electricity production from geothermal resources located predominantly in the Menderes Massif. Although geothermal exploitation is increasingly ongoing, geological, and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood. Several studies on the Menderes Massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin. This paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs. On the basis of field studies, we suggest that crustal-scale low-angle normal faults convey hot fluids to the surface and represent the first-order control on geothermal systems. At the basin scale, connected on low-angle normal faults, kilometric high-angle transfer faults are characterized by dilational jogs, where fluids may be strongly focused. In addition, favourable lithologies in the basement (e.g., karstic marble) could play a critical role in the localization of geothermal reservoirs. Finally, a compilation of geochemical data at the scale of the Menderes Massif suggests an important role of the large mantle thermal anomaly, which is related to the Hellenic subduction. Heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low-angle faults. Hence, geothermal activity in the Menderes Massif is not of magmatic origin but rather associated with active extensional tectonics related to the Aegean slab dynamics (i.e., slab retreat and tearing).

Geochemical characteristics of thermal waters of Hrvatsko zagorje

In the region of Hrvatsko zagorje there are a lot of spa localities. The study area is in the northern Pannonian part of Croatia which is characterized by a high geothermal gradient (0.049 °C/m) and surface heat flow (76 mW/m 2 ). Al- though there are a lot of thermal occurrences in the study area, only ten were taken into consideration because there was a lack of geochemical data at other locations. The thermal springs considered are: Harina Zlaka, Krapinske top- lice, Tuheljske toplice, Stubicke toplice, Sutinske toplice, Semnicke toplice, Toplicica (Mađarevo), Toplicica (Gota- lovec), Podevcevo, Vraždinske toplice. A compilation of geochemical data from different sources together with our own measurements has been used in this study. The aim of this paper is to review the thermal waters' geochemical characteristics and demonstrate how these features can be used to discern their origin and the aquifer they equilibrat- ed with. The geochemical characteristics of thermal waters of the study area suggest that the water is in equilibrium with dolomite which means that dolomite is the thermal aquifer in the study area.

Quantifying crustal thickness variations in evolving orogens: Correlation between arc basalt composition and Moho depth

A compilation of geochemical data from >50 active volcanoes where seismically defined Moho depth measurements are available, representing most volcanic arcs around the world, indicates a relation exists between crustal thickness (Moho depth) and the trace element composition of basalts. The best correlation exists for maximum light/heavy rare earth element (REE) ratios, and we use maximum Ce/Y (R2 = 0.90) to show the exponential function with increasing depth, to 50 km. Application to New Zealand, part of the eastern Gondwanan margin through much of the Phanerozoic, shows that higher Ce/Y ratios in arc basalts correspond to two periods of recognized crustal thickening, plus an additional event at ca. 240 Ma, which links New Zealand to the Gondwanide Orogeny. Conversely, low Ce/Y ratios in basalts correlate with periods of recognized extension in eastern Gondwana. Very high Ce/Y ratios in ca. 120 Ma rocks imply an unusually thickened (∼50 km) arc crust, consistent with independent geological estimates of crustal thickness at that time. The correlation shows that crustal thickness variations during orogenesis can be conservatively estimated to within ±3 km.

Ti/Nb ratios of clastic terrigenous sediments used as an indicator of provenance

Geochemical data have been compiled for the clastic sedimentary rocks of Late Proterozoic to Carboniferous age in the Armorican Massif (northwest France). These data show a great similarity in the distribution of Ti and Nb in most sediments due to an association of these elements during geochemical processes. The Ti/Nb ratios remain close to 300, a result which is interpreted as being an inheritance from the source areas. However, recent published works have indicated that Ti and Nb are not fractionated by either weathering or diagenetic phenomena. In contrast to all the other formations studied, the basal Carboniferous clastic rocks are different in having abnormally low Ti/Nb ratios (< 100). The origin of this anomaly is to be sought in the widespread intra-plate volcanism developed during the Devonian and Early Carboniferous. This phase of magmatic activity is characterized by low Ti/Nb ratios in acid differentiates. Compilation of geochemical data on recent volcanic suites shows that Ti/Nb ratios are a possible indicator of mantle supply in clastic rocks.