Natural trace element salinization of the Jemez River, New Mexico by geothermal springs and major tributaries

The Jemez River (JR), a tributary of the Rio Grande, is in north-central New Mexico within the Jemez Mountains, which houses the active, high-temperature (≤ 300 oC), liquid-dominated Valles Caldera geothermal system (VC). This work focuses on the northern portion of the JR, spanning a reach from the East Fork JR to the town of San Ysidro. Previous decadal work during low-flow or baseflow conditions (~10-20 cfs) has identified and characterized significant major-solute contributions from two outflow expressions of the VC, Soda Dam Springs and Jemez Hot Springs, and two major tributaries, Rio San Antonio and Rio Guadalupe. There is generally a net ~500-ppm increase from below Soda Dam to the end of the study segment. The distribution of concentrations of twenty-four trace metals from recent Fall 2017 sampling are defined by range from \u27ultra-trace\u27 levels (0.1-1 ppb) to measurements as much as 1 ppm. A set of elements (e.g., As, Li, Rb, Ba, Ti) follows the same downstream behavior of major ions, which is characterized by an increase in concentrations at each inflow and the observed greatest contribution (as much as an order of magnitude) is at Soda Dam. Another group (e.g., U, Al, Fe, Mn, Se) shows complex downstream patterns, which may be a result of non-conservative processes, such as precipitation/dissolution, sorption, and complexation. We attempt to resolve these potential in-stream processes with high-resolution (regular 1-km spacing with interspersed 50-m intervals around sites with complete chemistry) spatial surveys of temperature, dissolved oxygen, pH, oxidation-reduction potential, and turbidity

Manganese-Iron Phosphate Nodules at the Groken Site, Gale Crater, Mars

The MSL Curiosity rover investigated dark, Mn-P-enriched nodules in shallow lacustrine/fluvial sediments at the Groken site in Glen Torridon, Gale Crater, Mars. Applying all relevant information from the rover, the nodules are interpreted as pseudomorphs after original crystals of vivianite, (Fe2+,Mn2+)3(PO4)2·8H2O, that cemented the sediment soon after deposition. The nodules appear to have flat faces and linear boundaries and stand above the surrounding siltstone. ChemCam LIBS (laser-induced breakdown spectrometry) shows that the nodules have MnO abundances approximately twenty times those of the surrounding siltstone matrix, contain little CaO, and have SiO2 and Al2O3 abundances similar to those of the siltstone. A deconvolution of APXS analyses of nodule-bearing targets, interpreted here as representing the nodules’ non-silicate components, shows high concentrations of MnO, P2O5, and FeO and a molar ratio P/Mn = 2. Visible to near-infrared reflectance of the nodules (by ChemCam passive and Mastcam multispectral) is dark and relatively flat, consistent with a mixture of host siltstone, hematite, and a dark spectrally bland material (like pyrolusite, MnO2). A drill sample at the site is shown to contain minimal nodule material, implying that analyses by the CheMin and SAM instruments do not constrain the nodules’ mineralogy or composition. The fact that the nodules contain P and Mn in a small molar integer ratio, P/Mn = 2, suggests that the nodules contained a stoichiometric Mn-phosphate mineral, in which Fe did (i.e., could) not substitute for Mn. The most likely such minerals are laueite and strunzite, (Fe2+,Mn2+)3(PO4)2·8H2O and –6H2O, respectively, which occur on Earth as alteration products of other Mn-bearing phosphates including vivianite. Vivianite is a common primary and diagenetic precipitate from low-oxygen, P-enriched waters. Calculated phase equilibria show Mn-bearing vivianite could be replaced by laueite or strunzite and then by hematite plus pyrolusite as the system became more oxidizing and acidic. These data suggest that the nodules originated as vivianite, forming as euhedral crystals in the sediment, enclosing sediment grains as they grew. After formation, the nodules were oxidized—first to laueite/strunzite yielding the diagnostic P/Mn ratio, and then to hematite plus an undefined Mn oxy-hydroxide (like pyrolusite). The limited occurrence of these Mn-Fe-P nodules, both in space and time (i.e., stratigraphic position), suggests a local control on their origin. By terrestrial analogies, it is possible that the nodules precipitated near a spring or seep of Mn-rich water, generated during alteration of olivine in the underlying sediments

Depositional environments and paleolimnology of an ancient caldera lake: Oligocene Creede Formation, Colorado

The Oligocene Creede Formation represents an exceptionally well-preserved intracaldera sedimentary sequence within a large, resurgent caldera. The tuffaceous, epiclastic, and limestone deposits observed in surface exposures and Continental Scientific Drilling Program (CSDP) core provide a record of depositional processes and basin evolution following caldera collapse. The basal part of the Creede Formation is characterized by interbedded caldera wall-derived debris-flow breccias and ephemeral lake deposits. This unit is succeeded by deep-water lacustrine beds that constitute the bulk of the Creede Formation. Interbedded fallout tuffs from intracaldera volcanic eruptions significantly affected lacustrine sedimentation patterns and provide a means of basinwide correlation. Prominent sublacustrine travertine accumulations circumscribe the margins of the moat basin and probably outline the structural margin of the caldera. Deposition in a cool, montane climate is indicated by the presence of pseudomorphs after ikaite in the travertine and lake beds, and corroborative paleofloral analyses. Distinctive lowstand (shallow lake) and highstand (deep lake) facies-association distributions were deposited. Changes in the proportion and character of lowstand versus highstand sequences imply an evolution from a narrow, deep, steep-walled basin to a broad, shallow, incised basin through time. Carbonate minerals were deposited in the lake as travertine at spring-orifices, and as suspension-fallout laminae across the bottom. Little evidence for shelly or fish fauna is preserved in the lake beds. The character of the laminated strata and abundance of depositional carbonate suggest that the lake evolved into a permanently stratified, bicarbonate lake. The volume and mineralogy of depositional carbonate changed through time, but evidence for development of hypersaline, alkaline lake-water compositions is not observed. The level of basin-fill and geomorphic considerations preclude con-trol of lake level by a hydrologic sill; thus, the basin hydrology appears to have been controlled through a combination of climate and groundwater seepage. The deposits of the Creede Formation closely resemble those in modern and ancient caldera and crater lake basins. The effects of volcanism on detrital lacustrine sedimentation are profound; however, the influences on lake chemistry and biology are less clear. The extensive travertine in the Creede Formation appears to be related to the volcanic setting, although the origin is as of yet unclear

Sedimentary petrology and authigenic mineral distributions in the Oligocene Creede Formation, Colorado, United States

The Oligocene Creede Formation is an exceptionally well-preserved intracaldera sedimentary sequence within a large resurgent caldera. The tuffaceous, epiclastic, and limestone deposits observed in surface exposures and Continental Scientific Drilling Program (CSDP) core provide a record of depositional and mineral-water interaction processes following caldera collapse. The authigenic mineral distributions also provide information regarding the role of the Creede Formation in the ancient Creede hydrothermal system. The basal part of the Creede Formation is characterized by interbedded calderawall-derived debris-flow breccias, alluvial, and shallow lacustrine deposits. This unit is succeeded by deep-water lacustrine beds that constitute the bulk of the Creede Formation. Interbedded fallout tuffs from intracaldera volcanic eruptions significantly affected lacustrine sedimentation patterns and provide a means of basin-wide correlation. Carbonate minerals were deposited as travertine at spring orifices and as suspension-fallout (micrite and micritic peloids) laminae across the lake bottom. The travertine accumulations circumscribe the margins of the moat basin and probably outline the structural margin of the caldera. Most of the detrital sediment within the Creede strata was derived from reworking of Fisher Quartz Latite fallout ash and erosion of the caldera walls. Calcareous and tuffaceous siltstone intraclasts are common in most coarse-grained lacustrine lithologies, especially in beds deposited after the emplacement of the H fallout tuff. Most of the identifiable ash-flow tuff lithic fragments in the coarser grained beds can be ascribed to one of the Carpenter Ridge Tuffs or the Wason Park Tuff. Fragments from a variety of intermediate composition lavas are also common in most beds. Fragments of crystal-rich ashflow tuff units are generally less abundant, although clasts of Snowshoe Mountain Tuff and Fish Canyon Tuff are locally present in various parts of the caldera. Clasts of tuffs associated with formation of the San Luis caldera may be present in the lithic composition of Creede sediments, although confirmation awaits more definitive petrographic analysis of the Creede Formation and San Luis caldera ash-flow tuffs. The relative rarity of Snowshoe Mountain Tuff in the Creede Formation, even in the upper part of the section, is surprising and alludes to the unusual character of this ash-flow tuff unit. Hydrolysis and dissolution of the ash are interpreted to have led to formation of smectite, phillipsite(?), clinoptilolite, erionite, potassium feldspar, and quartz during burial diagenesis under a high geothermal gradient. The formation of phillipsite is inferred from pseudomorphic structures and may reflect increased alkalinity in the lake waters during the latter part of the lake history. The effects of two major low-temperature hydrothermal events are superimposed on diagenesis. The Antlers Park event resulted in replacement of the smectite and zeolite diagene tic assemblage by analcime,chlorite, and chlorite/smectite mixed-layered clay in the northwestern part of the moat. The Creede hydrothermal event is interpreted to have produced various silica minerals, illite, and potassium feldspar observed above 400 m in the formation in the northeastern part of the basin. In both events, the patterns of alteration indicate that faults and coarse-grained deltaic and lacustrine fan deposits served as pathways for fluid movement through the formation. The alteration associated with the Creede hydrothermal event seems to have resulted from reactions associated with conductive cooling of the hydrothermal fluid and mixing with diagenetic fluids. The pattern of alteration suggests that the hydrothermal plume flowed laterally into the Creede Formation from the faultcontrolled Creede mineral district to the north of the caldera. Diagenetic reactions in the tuffaceous strata probably resulted in saline, alkaline fluids, especially in the upper part of the formation. Initiation of faulting and hydrothermal fluid flow in the Creede hydrothermal system could have allowed diagenetic pore waters from the Creede Formation to recharge the hydrothermal flow cell. The chemical evolution of the diagenetic fluids in the hydrothermal system has not been investigated, but is required to address the problem further

U-series geochronology of large-volume Quaternary travertine deposits of the southeastern Colorado Plateau: Evaluating episodicity and tectonic and paleohydrologic controls

Large-volume travertine deposits in the southeastern Colorado Plateau of New Mexico and Arizona, USA, occur along the Jemez lineament and Rio Grande rift. These groundwater discharge deposits reflect vent locations for mantle-derived CO2 , which was conveyed by deeply sourced hydrothermal fluid input into springs. U-series dating of stratigraphic sections shows that major aggradation and large-volume (2.5 km3 ) deposition took place across the region episodically at 700–500 ka, 350–200 ka, and 100–40 ka. These pulses of travertine formation coincide with the occurrence of regional basaltic volcanism, which implies an association of travertine deposits with underlying low-velocity mantle that could supply the excess CO2 . The calculation of landscape denudation rates based on basalt paleosurfaces shows that travertine platforms developed on local topographic highs that required artesian head and fault conduits. Episodic travertine accumulation that led to the formation of the observed travertine platforms represents conditions when fault conduits, high hydraulic head, and high CO2 flux within confined aquifer systems were all favorable for facilitating large-volume travertine formation, which was therefore controlled by tectonic activity and paleohydrology. By analogy to the active Springerville–St. Johns CO2 gas fi eld, the large volumes and similar platform geometries of travertine occurrences in this study are interpreted to represent extinct CO2 gas reservoirs that were vents for degassing of mantle volatiles into the near-surface system

Geomicrobiology of Cave Ferromanganese Deposits: A Field and Laboratory Investigation

Unusual ferromanganese deposits are found in several caves in New Mexico. The deposits are enriched in iron and manganese by as much as three orders of magnitude over the bedrock, differing significantly in mineralogy and chemistry from bedrock-derived insoluble residue. The deposits contain metabolically active microbial communities. Enrichment cultures inoculated from the ferromanganese deposits produced manganese oxides that were initially amorphous but developed into crystalline minerals over an 8-month period and beyond; no such progression occurred in killed controls. Phylogenetic analyses of sequences from clone libraries constructed from culture DNA identified two genera known to oxidize manganese, but most clones represent previously unknown manganese oxidizers. We suggest that this community is breaking down the bedrock and accumulating iron and manganese oxides in an oligotrophic environment

Diverse microbial communities inhabiting ferromanganese deposits in Lechuguilla and Spider Caves

Lechuguilla Cave is an ancient, deep, oligotrophic subterranean environment that contains an abundance of low‐density ferromanganese deposits, the origin of which is uncertain. To assess the possibility that biotic factors may be involved in the production of these deposits and to investigate the nature of the microbial community in these materials, we carried out culture‐independent, small subunit ribosomal RNA (SSU rRNA) sequence‐based studies from two sites and from manganese and iron enrichment cultures inoculated with ferromanganese deposits from Lechuguilla and Spider Caves. Sequence analysis showed the presence of some organisms whose closest relatives are known iron‐ and manganese‐oxidizing/reducing bacteria, including Hyphomicrobium, Pedomicrobium, Leptospirillum, Stenotrophomonas and Pantoea. The dominant clone types in one site grouped with mesophilic Archaea in both the Crenarchaeota and Euryarchaeota. The second site was dominated almost entirely by lactobacilli. Other clone sequences were most closely related to those of nitrite‐oxidizing bacteria, nitrogen‐fixing bacteria, actinomycetes and β‐ and γ‐Proteobacteria. Geochemical analyses showed a fourfold enrichment of oxidized iron and manganese from bedrock to darkest ferromanganese deposits. These data support our hypothesis that microorganisms may contribute to the formation of manganese and iron oxide‐rich deposits and a diverse microbial community is present in these unusual secondary mineral formations

Evidence for geomicrobiological interactions in Guadalupe caves

Caves in the Guadalupe Mountains offer intriguing examples of possible past or present geomicrobiological interactions within features such as corrosion residues, pool fingers, webulites, u-loops, and moonmilk. Scanning electron microscopy, transmission electron microscopy, molecular biology techniques, enrichment cultures, bulk chemistry, and X-ray diffraction techniques have revealed the presence of iron- and manganese-oxidizing bacteria in corrosion residues, which supports the hypothesis that these organisms utilize reduced iron and manganese from the limestone, leaving behind oxidized iron and manganese. Metabolically active populations of bacteria are also found in “punk rock” beneath the corrosion residues. Microscopic examination of pool fingers demonstrates that microorganisms can be inadvertently caught and buried in pool fingers, or can be more active participants in their formation. Enrichment cultures of moonmilk demonstrate the presence of a variety of microorganisms. Humans can have a deleterious impact on microbial communities in Guadalupe cave