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Title: Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas

Abstract

Hydrocarbons, native sulfur, Mississippi Valley-type (MVT) deposits, and sulfuric acid karst in the Delaware Basin, southeastern New Mexico, and west Texas, USA, are all genetically related through a series of sulfur redox reactions. The relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light ({delta}{sup 34}S = -22 to -12) H{sub 2}S and bioepigenetic limestone (castiles). This light H{sub 2}S was then oxidized at the redox interface to produce economic native sulfur deposits ({delta}{sup 34}S = -15 to +9) in the castiles, paleokarst, and along graben-boundary faults. This isotopically light H{sub 2}S also migrated from the basin into its margins to accumulate in structural (anticlinal) and stratigraphic (Yates siltstone) traps, where it formed MVT deposits within the zone of reduction ({delta}{sup 34}S = -15 to +7). Later in time, in the zone of oxidation, this H{sub 2}S reacted with oxygenated water to produce sulfuric acid, which dissolved the caves (e.g., Carlsbad Cavern and Lechuguilla Cave, Guadalupe Mountains). Massive gypsum blocks on the floors of the caves ({delta}{sup 34}S = -25 to +4) were formed as a result of this reaction. The H{sub 2}S also produced isotopically light cave sulfur ({delta}{sup 34}Smore » = -24 to -15), which is now slowly oxidizing to gypsum in the presence of vadose drip water. 16 refs., 10 figs.« less

Authors:
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
61805
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Geology (New York); Journal Volume: 25; Journal Issue: 1; Other Information: PBD: Feb 1995
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; HYDROCARBONS; GEOLOGIC DEPOSITS; SULFUR; REDOX REACTIONS; EVAPORITES

Citation Formats

Hill, C.A. Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas. United States: N. p., 1995. Web. doi:10.1007/BF01061826.
Hill, C.A. Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas. United States. doi:10.1007/BF01061826.
Hill, C.A. Wed . "Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas". United States. doi:10.1007/BF01061826.
@article{osti_61805,
title = {Sulfur redox reactions: Hydrocarbons, native sulfur, Mississippi Valley-type deposits, and sulfuric acid karst in the Delaware Basin, New Mexico and Texas},
author = {Hill, C.A.},
abstractNote = {Hydrocarbons, native sulfur, Mississippi Valley-type (MVT) deposits, and sulfuric acid karst in the Delaware Basin, southeastern New Mexico, and west Texas, USA, are all genetically related through a series of sulfur redox reactions. The relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light ({delta}{sup 34}S = -22 to -12) H{sub 2}S and bioepigenetic limestone (castiles). This light H{sub 2}S was then oxidized at the redox interface to produce economic native sulfur deposits ({delta}{sup 34}S = -15 to +9) in the castiles, paleokarst, and along graben-boundary faults. This isotopically light H{sub 2}S also migrated from the basin into its margins to accumulate in structural (anticlinal) and stratigraphic (Yates siltstone) traps, where it formed MVT deposits within the zone of reduction ({delta}{sup 34}S = -15 to +7). Later in time, in the zone of oxidation, this H{sub 2}S reacted with oxygenated water to produce sulfuric acid, which dissolved the caves (e.g., Carlsbad Cavern and Lechuguilla Cave, Guadalupe Mountains). Massive gypsum blocks on the floors of the caves ({delta}{sup 34}S = -25 to +4) were formed as a result of this reaction. The H{sub 2}S also produced isotopically light cave sulfur ({delta}{sup 34}S = -24 to -15), which is now slowly oxidizing to gypsum in the presence of vadose drip water. 16 refs., 10 figs.},
doi = {10.1007/BF01061826},
journal = {Environmental Geology (New York)},
number = 1,
volume = 25,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 1995},
month = {Wed Feb 01 00:00:00 EST 1995}
}
  • The Delaware Basin of southeastern New Mexico and West Texas contains hydrocarbons and native sulfur in the basin and sulfuric acid-formed caves and Mississippi Valley-type (MVT) ore deposits around the margins of the basin. Hydrocarbons reacting with sulfate evaporite rock produced hydrogen sulfide gas, which gas oxidized to native sulfur in the basin and which gas also migrated from basin to reef and accumulated there in structural and stratigraphic traps. In the reduced zone of the carbonate reef margin the H[sub 2]S combined with metal-chloride complexes to form MVTs, and in the oxidized zone later in time the H[sub 2]Smore » formed sulfuric acid which dissolved out the famous caves of the region (e.g., Carlsbad Cavern, Lechuguilla Cave). Sulfuric acid karst can be recognized by the discontinuity, large size, and spongework nature of its cave passages, and by the presence of native sulfur, endellite, and large gypsum deposits within these caves. Sulfuric acid oilfield karst refers to cavernous porosity filled with hydrocarbons and can be produced by the mixing of waters of different H[sub 2]S content or by the oxidation of H[sub 2]S to sulfuric acid. Sulfur and carbon-oxygen isotopes have been used to establish and trace the sequence of related hydrocarbon, sulfur, MVT, and karst events in the Delaware Basin.« less
  • Sulfur-isotope data and pH-dependence of the mineral endellite support the hypothesis that Carlsbad Cavern and other caves in the Guadalupe Mountains were dissolved primarily by sulfuric acid rather than by carbonic acid. Floor gypsum deposits up to 10 m thick and native sulfur in the caves are significantly enriched in {sup 32}S; {delta}{sup 34}S values as low as {minus}25.8 {per thousand} (CDT) indicate that the cave sulfur and gypsum are the end products of microbial reactions associated with hydrocarbons. A model for a genetic connection between hydrocarbons in the basin and caves in the Guadalupe Mountains is proposed. As themore » Guadalupe Mountains were uplifted during the late Pliocene-Pleistocene, oil and gas moved updip in the basin. The gas reacted with sulfate anions derived from dissolution of the Castile anhydrite to form H{sub 2}S, CO{sub 2}, and castile limestone. The hydrogen sulfide rose into the Capitan reef along joints, forereef carbonate beds, or Bell Canyon siliciclastic beds and there reacted with oxygenated groundwater to form sulfuric acid and Carlsbad Cavern. A sulfuric-acid mode of dissolution may be responsible for large-scale porosity of some Delaware basin reservoirs and for oil-field karst reservoirs in other petroleum basins of the world. 8 figs.« less
  • Mississippi Valley-type Pb-Zn mineralization occurs in Lower Permian (Leonardian) shelf-margin dolomites rimming an inner-shelf, carbonate-evaporite province on the southern Central Basin platform. The sulfide-hosting dolomites pass abruptly along a bounding fault system into basinal facies of the coeval Bone Spring formation. Zoned sphalerite and lesser amounts of galena and pyrite are the major sulfides present in this occurrence. Sulfur isotopes and fluid inclusions, in conjunction with considerations of the burial history of the area, suggest that Pb-Zn precipitation occurred during the late Mesozoic to Tertiary, in contact with mineralizing fluids heated to 96/sup 0/-122/sup 0/C (205/sup 0/-252/sup 0/F). These fluidsmore » were likely discharged along the Central Basin platform from basin aquifers that are part of a regional, eastward, gravity-driven flow system that has been operative since at least the Tertiary. Sulfide precipitation appears to have resulted from mixing of basinal brines and ambient host fluids that were charged with sulfur derived from laterally contiguous shelf evaporites. Burial paragenesis of the shelf-margin host involved several episodes of eogenetic and mesogenetic dolomitization and partial dissolution (ground preparation) prior to and partly concurrent with sulfide emplacement. The occlusion of some pores by coarse-crystalline, luminescent-banded dolomite and calcite cements subsequent to mineralization is the last diagenetic event recognized in the host carbonates. 8 figures.« less
  • The Guadalupian Delaware Mountain Group is a 1000-1600-m (3281-5250-ft) thick section of siltstone and sandstone deposited in a deep-water density-stratified basin surrounded by carbonate banks or reefs and broad shallow evaporite-clastic shelves. The most prevalent style of basinal deposition was suspension settling of silt. Laminated siltstone beds are laterally extensive and cover basin-floor topographic irregularities and flat-floored channels as much as 30 m (99 ft) deep and 1 km or more wide. Channels can be observed in outcrop at the basin margin and can be inferred from closely spaced wells in the basin. The channels are straight to slightly sinuous,more » trend at high angles to the basin margin, and extend at least 70 km (43 mi) into the basin. Sandstone beds, confined to channels, form numerous stratigraphic traps. Hydrocarbon sealing beds are provided by laminated organic siltstone, which laterally can form the erosional margin where channels are cut into siltstone beds. Thick beds of very fine-grained sandstones fill the channels. These sandstones contain abundant large and small-scale traction-current-produced stratification. These sandy channel deposits generally lack texturally graded sedimentation units and show no regular vertical sequence of stratification types or bed thickness. Exploration predictions based on submarine fan models formed by turbidity currents would anticipate very different proximal-distal changes in sandstone geometry and facies. 16 figures.« less
  • This study evaluated Na-Cl-Br systematics of fluid inclusion-hosted brines in Mississippi Valley-type (MVT) deposits from the Appalachian Basin. Unlike other geochemical tracers such as lead and strontium isotopes which constrain metal sources, Na-Cl-Br systematics identify sources of brine salinity. Saline formation waters can vary systematically within and between basins with regard to their Na-Cl-Br compositions depending on the importance of halite dissolution relative to retention of subaerially evaporated seawater for the halogen budget. Oil field brine compositions from the Illinois and Appalachian basins are quite distinct in their Na-Cl-Br systematics. Compositions of saline fluid inclusions in MVT deposits generally aremore » consistent with these regional differences. These results shed new light on the extent of regional flow systems and on the geochemical evolution of saline fluids responsible for mineralization. Nearly all fluid inclusions analyzed from the Appalachian MVT deposits have Na/Br and Cl/Br ratios less than modern seawater, consistent with ratios observed in marine brines involved in halite precipitation. The Na-Cl-Br systematics of the brines responsible for Appalachian MVT deposits may be inherited from original marine brines refluxed into the porous carbonate shelf sediments that host these deposits. The Cl/Br and Na/Br ratios of most fluid inclusion-hosted brines from Appalachian MVT sphalerites and fluorites fall into two compositional groups, one from the Lower Cambrian paleoaquifer and another from the Lower Ordovician paleoaquifer. Leachates from most MVT barite deposits form a third compositional group having lower Na/Br and Cl/Br ratios than the other two. Appalachian MVT leachate compositions differ significantly from those in MVT deposits in the Cincinnati arch-midcontinent region suggesting that these two MVT provinces formed from brines of different origin or flow path. 59 refs., 8 figs., 2 tabs.« less