From deep to shallow fluid reservoirs: evolution of fluid sources during exhumation of the Sierra Almagrera,Betic Cordillera,Spain

The combination of structural, geochemical and palaeotopographic data proves to be an efficient tool to understand fluid transfers in the crust. This study discriminates shallow and deep fluid reservoirs on both sides of the brittle–ductile transition under an extensional regime and points out the role of major transcurrent fault activity in this palaeohydrogeological setting. Palaeofluids trapped in quartz and siderite–barite veins record the transfer of fluids and metal solute species during the Neogene exhumation of the Sierra Almagrera metamorphic belt. Ductile then brittle–ductile extensional quartz veins formed from a deep fluid reservoir, trapping metamorphic secondary brines containing low‐density volatile phases derived from the dissolution of Triassic evaporites. During exhumation, low‐salinity fluids percolated within the brittle domain, as shown by transgranular fluid inclusion planes affecting previous veins. These observations indicate the opening of the system during Serravalian to early Tortonian times and provide evidence for the penetration of surficial fluids of meteoric or basinal origin into the upper part of the brittle–ductile transition. During exhumation, synsedimentary transcurrent tectonic processes occurred from late Tortonian times onwards, while marine conditions prevailed at the Earth's surface. At depth in the brittle domain, quartz veins associated with haematite record a return to high‐salinity fluid circulation suggesting an upward transfer fed from a lower reservoir. During the Messinian, ongoing activity of the trans‐Alboran tectono‐volcanic trend led to the formation of ore deposits. Reducing fluids caused the formation of siderite and pyrite ores. The subsequent formation of galena and barite may be related to an increase of temperature. The high salinity and Cl/Br ratio of the fluids suggest another source of secondary brine derived from dissolved Messinian evaporites, as corroborated by the δ³⁴S signature of barite. These evaporites preceded the main sea‐level drop related to the peak of the salinity crisis (5.60–5.46 Ma).     

Unintended effects of technology on climate change adaptation: an historical analysis of water conflicts below Andean Glaciers

Climate change adaptation measures can generate long-term unintended consequences, as this paper demonstrates through an empirical case study of water conflicts at Lake Parón in Peru’s Cordillera Blanca mountain range. This decade-long struggle culminated in 2008 when a coalition of local groups (stakeholders) from the Cruz de Mayo and Caraz communities in the Callejón de Huaylas seized control of the Lake Parón reservoir from a private multinational corporation, Duke Energy. This clash over Parón’s water in the Llullán and Santa River watersheds emerged much earlier than climatic-hydrologic models had predicted, and it occurred, this paper argues, largely because of previously successful climate adaptation measures. The drainage tunnel and floodgates originally installed at Parón in the 1980s to prevent a climate-related outburst flood led to unintended or perverse outcomes because these technological artifacts subsequently allowed a diversity of stakeholders—including rural subsistence farmers, urban residents, national park officials, tourism promoters, the state energy company Electroperú, and Duke Energy—to manage water differently depending on their priorities and the existing governance structures. Neoliberal reforms that altered state-society-environment relations in Peru played a key role in these changing stakeholder power dynamics that were reflected in the management of water infrastructure at Parón. Examining this water conflict that emerged from the unintended effects of climate adaptation demonstrates not only how technology and society are mutually constitutive, but also why the politics of technologies must be considered more carefully in the analysis of social-ecological systems, hydro-social cycles, and climate change adaptation.     

New and past geochemical data on fresh to brine waters of the Salar de Atacama and Andean Altiplano,northern Chile

The paper deals with the major chemistry and stable isotopes (hydrogen, oxygen, carbon, sulfur, strontium) of waters and solutes from the Salar de Atacama basin (Rio Pedro, Honar Creek and Laguna Chaxa) and Andean Altiplano (Laguna Miñique and Laguna Miscanti). The water inflows of the Salar are chemically quite different, the Rio San Pedro being of Na‐Cl type and the Honar Creek of Na‐HCO₃ type, in keeping with the sedimentary‐evaporitic and volcanic nature of the catchment rocks respectively. The δ³⁴S and δ¹⁸O values of sulfate and the ⁸⁷Sr/⁸⁶Sr ratio of strontium in the streams match those of drained rocks, whereas the δ¹³C values of dissolved carbonate are largely controlled by vegetation. The lagoons are evaporated meteoric water bodies, and the relative air humidity estimated from the slope of the isotopic evaporation line is in accordance with historical data on air humidity in the area. The Laguna Chaxa is Na‐Cl rich, and its isotopic composition are consistent with a mixed sedimentary‐volcanic provenance of sulfur and strontium solutes. The Laguna Miñique is Na‐SO₄ rich, and its sulfate δ³⁴S is nearly identical to that of Laguna Chaxa. The δ¹³C(HCO₃) values are quite different in the Laguna Chaxa and Laguna Miñique, with the former being notably enriched in ¹³C probably because of preferential uptake of ¹²C by the high biological productivity occurring in the lagoon. The limited set of new data is interpreted in the context of a much larger literature database. In particular, previous chemical data on inflows and brines in the Salar de Atacama were revisited, and compared with evaporation path models and mineral stability diagrams (boron, lithium and Mg‐minerals) computed using updated software and thermodynamic databases. The modeling shows that the removal of boron and lithium from sulfate‐rich brines possibly occurs, respectively, as ulexite and sulfate salts, and carnallite should be the final magnesium phase of the brine evolution.