干旱区生态环境知识资源中心(Arid): On the origin of saline compounds in acidic salt flats (Central Andean Altiplano)

Arid

DOI	10.1016/j.chemgeo.2021.120155
	On the origin of saline compounds in acidic salt flats (Central Andean Altiplano)
	Pueyo, JuanJose; Demergasso, Cecilia; Escudero, Lorena; Chong, Guillermo; Cortez-Rivera, Paulina; Sanjurjo-Sanchez, Jorge; Carmona, Virginia; Giralt, Santiago
通讯作者	Pueyo, J (corresponding author), Univ Barcelona, Fac Ciencies Terra, C Marti i Franques S-N, Barcelona 08028, Spain.
来源期刊	CHEMICAL GEOLOGY
ISSN	0009-2541
EISSN	1872-6836
出版年	2021
卷号	574
英文摘要	Volcanism, aridity, and endorheism converge in the central zone of the Andean Cordillera (Bolivia, Chile, and Argentina, between latitudes 19 degrees S and 27 degrees S). The Gorbea and Ignorado basins are pristine Andean sites in which the transfer of saline compounds from endogenous to exogenous environments occurs. In this area the regional volcanic rocks display strong argillic alteration, with Al and Fe (alunite, jarosite) and Ca (gypsum/anhydrite) sulfates. Native sulfur is also present in paleosolfataras. The Gorbea salt flat is covered by a discontinuous layer of selenitic gypsum of varying thickness (maximum 2 m). The discontinuity of the layer as well as its variable thickness is due to the fact that the original bed has been partially destroyed mainly by dissolution but also by deflation. Saline pond brines (Cl-SO4-Na [-Mg]) are strongly acidic reaching pH values lower than 2. The high temperature processes that caused the hydrothermal alteration in the Gorbea and Ignorado basins occurred in the Miocene (14 Ma) coinciding with a wet period that reached 9 Ma. Subsequently, the weather up to 120 ka was predominantly hyper-arid with a less arid interval between 6 and 3 Ma and the epithermal sulfates were recycled in saline lakes mainly in the Late Pleistocene wet period (120 to 11.7 ka). Evolution into the current salt flat occurred in the mid-early Holocene (11.7 to 4 ka), through a salt lake that first evolved into a `salina' environment that gave rise to a selenitic gypsum layer (6.4 ka), and later to the final dryness. The highest values of delta S-34(VCDT) and delta O-18(VSMOW) found in the selenitic gypsum layer (+20 parts per thousand and + 28 parts per thousand, respectively) show that the recycling was locally produced, mainly from isotopically heavier hypogene sulfates. The delta O-18(VSMOW) (and less clearly, delta S-34(VCDT)) values are higher in the basal part of the gypsum crust (about +27 parts per thousand), which suggests an initial hypogene source that decreased towards the top due to mixing with supergene sulfate inputs. Bacterial activity, although catalyzing the supergene reactions, does not appear to have had a significant influence on the isotopic composition of sulfates. The crystallization water of the gypsum is isotopically lighter in the basal part of the selenitic layer (delta O-18(VSMOW) approximate to +7 parts per thousand), which indicates that the brines of the saline lake were still poorly evolved. These brines evolved to heavier (approximately +13 parts per thousand) towards the top of the layer and towards the center of the salt flat, before the final drying. The partial destruction of the selenitic gypsum layer occurred during more recent wet periods over the last 4 ka that have been identified in wetlands and lakes in the Central Andean area. Isotopic data (delta S-34(VCDT) and delta O-18(VSMOW)) clearly suggest that sulfates in the saline compounds and evaporites from the entire Central Andean arid area have mostly a thermal origin with contributions from atmospheric deposition and locally, near the Pacific coast, marine aerosols. In addition, the great difference in altitude (approximately 3000 m) between the Altiplano and the lands located to the west, up to the Pacific coast, generated a constant flow of groundwater containing saline compounds that gave rise, to the salt flats of the basins located in lower topographic areas (Atacama, Punta Negra, Hilaricos, Soledad, Tamarugal, Salar de Pintados, Salar Grande) throughout the Cenozoic. Such salt flats have lower delta S-34(VCDT) and delta O-18(VSMOW) values mostly for two reasons: the secular mixing with atmospheric sulfate, and the isotope fractionation related to repetitive dissolution (or leaking)-migration-precipitation along the hydraulic gradient, a process that occurred throughout a large part of the Cenozoic. The last process also explains that the evaporites of some of these salt flats (e.g., Salar de Atacama, Salar Grande) display very high Cl/SO4 ratios.
英文关键词	Salar de Gorbea Acidic brines OSL dating delta S-34(VCDT) delta O-18(VSMOW) delta H-2(VSMOW) Sulfate recycling Jarosite Andean salt flats Microbial sulfur oxidation Thiotrophic microbial community
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000651246100002
WOS关键词	PORPHYRY COPPER TAILINGS ; STABLE-ISOTOPE GEOCHEMISTRY ; IBERIAN PYRITE BELT ; ATACAMA-DESERT ; MINE-DRAINAGE ; NORTHERN CHILE ; MICROBIAL COMMUNITIES ; SULFATE MINERALS ; VOLCANIC COMPLEX ; RIO-TINTO
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/349832
作者单位	[Pueyo, JuanJose] Univ Barcelona, Fac Ciencies Terra, C Marti i Franques S-N, Barcelona 08028, Spain; [Demergasso, Cecilia; Escudero, Lorena] Univ Catolica Norte, Ctr Biotecnol, Antofagasta, Chile; [Demergasso, Cecilia; Escudero, Lorena] Ctr Invest Cient & Tecnol Min, Antofagasta, Chile; [Chong, Guillermo; Cortez-Rivera, Paulina] Univ Catolica Norte, Dept Geol, Antofagasta, Chile; [Sanjurjo-Sanchez, Jorge] Univ A Coruna, Inst Univ Xeol, La Coruna, Spain; [Carmona, Virginia] Inst Joan Amigo, Lespluga De Francoli, Spain; [Giralt, Santiago] Geosci Barcelona Geo3BCN CSIC, Barcelona, Spain
推荐引用方式 GB/T 7714	Pueyo, JuanJose,Demergasso, Cecilia,Escudero, Lorena,et al. On the origin of saline compounds in acidic salt flats (Central Andean Altiplano)[J],2021,574.
APA	Pueyo, JuanJose.,Demergasso, Cecilia.,Escudero, Lorena.,Chong, Guillermo.,Cortez-Rivera, Paulina.,...&Giralt, Santiago.(2021).On the origin of saline compounds in acidic salt flats (Central Andean Altiplano).CHEMICAL GEOLOGY,574.
MLA	Pueyo, JuanJose,et al."On the origin of saline compounds in acidic salt flats (Central Andean Altiplano)".CHEMICAL GEOLOGY 574(2021).