Configuration of Columbia, a Mesoproterozoic Supercontinent

Orogenic gold and geologic time: a global synthesis

Timing of the collision between India and Asia is the key boundary condition in all models for the evolution of the Himalaya-Tibetan orogenic system. Thus it profoundly affects the interpretation of the rates of a multitude of associated geological processes ranging from Tibetan Plateau uplift through continental extrusion across eastern Asia, as well as our understanding of global climate change during the Cenozoic. Although an abrupt slowdown in the rate of convergence between India and Asia around 55 Ma is widely regarded as indicating the beginning of the collision, most of the effects attributed to this major tectonic episode do not occur until more than 20 Ma later. Refined estimates of the relative positions of India and Asia indicate that they were not close enough to one another to have collided at 55 Ma. On the basis of new field evidence from Tibet and a reassessment of published data we suggest that continent-continent collision began around the Eocene/Oligocene boundary (∼34 Ma) and propose an alternative explanation for events at 55 Ma.

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When and where did India and Asia collide

This paper presents a plate-scale model for the Precambrian growth and evolution of the North American continent. The core of the North American continent (Canadian shield) came together in the Paleoproterozoic (2.0–1.8 Ga) by plate collisions of Archean continents (Slave with Rae-Hearne, then Rae-Hearne with Superior) as well as smaller Archean continental fragments (Wyoming, Medicine Hat, Sask, Marshfield, Nain cratons). The resulting Trans-Hudson orogen was a collisional belt similar in scale to the modern Himalayas. It contains mainly reworked Archean crust, but remnants of juvenile volcanic belts are preserved between Archean masses. The thick, buoyant, and compositionally depleted mantle lithosphere that now underlies North America, although dominantly of Archean age, took its present shape by processes of collisional orogenesis and likely has a scale of mantle heterogeneity similar to that exhibited in the overlying crust.

In marked contrast, lithosphere of southern North America (much of the conti nental United States) was built by progressive addition of a series of dominantly juvenile vol canic arcs and oceanic terranes accreted along a long-lived southern (present coordinates) plate margin. Early juvenile additions (Pembine-Wausau, Elves Chasmarcs) formed at the same time (1.84–1.82 Ga) the core was assembling. Following final assembly of the Archean and Paleoproterozoic core of North America by 1.8 Ga, major accretionary provinces (defined mainly by isotopic model ages) were added by arc-continent accretion, analogous to present-day convergence between Australia and Indonesia. Also similar to Indonesia, some accreted terranes contain older continental crustal material [Archean(?) Mojavia], but the extent and geometry of older crust are not well known. Accretionary provinces are composed of numerous 10 to 100 km scale terranes or blocks, separated by shear zones, some of which had compound histories as terrane sutures and later crustal-assembly structures. Major northeast-trending provinces are the Yavapai province (1.80–1.70 Ga), welded to North America during the 1.71–1.68 Ga Yavapai orogeny; the Mazatzal province (1.70–1.65 Ga), added during the 1.65–1.60 Ga Mazatzal orogeny; the Granite-Rhyolite province (1.50–1.30 Ga), added during the 1.45–1.30 Ga tectonic event associated with A-type intracratonic magmatism; and the Llano-Grenville province (1.30–1.00 Ga), added during the 1.30–0.95 Ga broader Grenville orogeny. During each episode of addition of juvenile lithosphere, the transformation of juvenile crust into stable continental lithosphere was facilitated by voluminous granitoid plutonism that stitched new and existing orogenic boundaries. Slab roll back created transient extensional basins (1.70 and 1.65 Ga) in which Paleoproterozoic quartzite-rhyolite successions were deposited, then thrust imbricated as basins were inverted. The lithospheric collage that formed from dominantly juvenile terrane accretion and stabilization (1.8–1.0 Ga) makes up about half of the present-day North American continent. Throughout (and as a result of) this long-lived convergent cycle, mantle lithosphere below the accretionary provinces was more hydrous, fertile, and relatively weak compared to mantle lithosphere under the Archean core.

/pdf/tectonic-model-for-the-proterozoic-growth-of-north-america-15imlz45mt.pdf

Tectonic model for the Proterozoic growth of North America

Thermophilic and hyperthermophilic Archaea and Bacteria have been isolated from marine hydrothermal systems, heated sediments, continental solfataras, hot springs, water heaters, and industrial waste They catalyze a tremendous array of widely varying metabolic processes As determined in the laboratory, electron donors in thermophilic and hyperthermophilic microbial redox reactions include H2, Fe(2+), H2S, S, S2O3(2-), S4O6(2-), sulfide minerals, CH4, various mono-, di-, and hydroxy-carboxylic acids, alcohols, amino acids, and complex organic substrates; electron acceptors include O2, Fe(3+), CO2, CO, NO3(-), NO2(-), NO, N2O, SO4(2-), SO3(2-), S2O3(2-), and S Although many assimilatory and dissimilatory metabolic reactions have been identified for these groups of microorganisms, little attention has been paid to the energetics of these reactions In this review, standard molal Gibbs free energies (DeltaGr(0)) as a function of temperature to 200 degrees C are tabulated for 370 organic and inorganic redox, disproportionation, dissociation, hydrolysis, and solubility reactions directly or indirectly involved in microbial metabolism To calculate values of DeltaGr(0) for these and countless other reactions, the apparent standard molal Gibbs free energies of formation (DeltaG(0)) at temperatures to 200 degrees C are given for 307 solids, liquids, gases, and aqueous solutes It is shown that values of DeltaGr(0) for many microbially mediated reactions are highly temperature dependent, and that adopting values determined at 25 degrees C for systems at elevated temperatures introduces significant and unnecessary errors The metabolic processes considered here involve compounds that belong to the following chemical systems: H-O, H-O-N, H-O-S, H-O-N-S, H-O-C(inorganic), H-O-C, H-O-N-C, H-O-S-C, H-O-N-S-C(amino acids), H-O-S-C-metals/minerals, and H-O-P For four metabolic reactions of particular interest in thermophily and hyperthermophily (knallgas reaction, anaerobic sulfur and nitrate reduction, and autotrophic methanogenesis), values of the overall Gibbs free energy (DeltaGr) as a function of temperature are calculated for a wide range of chemical compositions likely to be present in near-surface and deep hydrothermal and geothermal systems

http://rcn.montana.edu/Resources/LRES555/Manuscripts/energetics.pdf

Energetics of overall metabolic reactions of thermophilic and hyperthermophilic Archaea and Bacteria

Research on the Precambrian basement of North America over the past two decades has shown that Archean and earliest Proterozoic evolution culminated in suturing of Archean cratonic elements and pre-1.80-Ga Proterozoic terranes to form the Canadian Shield at about 1.80 Ga (Hoffman, 1988,1989a, b). We will refer to this part of Laurentia as the Hudsonian craton (Fig. 1) because it was fused together about 1.80 to 1.85 Ga during the Trans-Hudson and Penokean orogenies (Hoffman, 1988). The Hudsonian craton, including its extensions into the United States (Chapters 2 and 3, this volume), formed the foreland against which 1.8- to 1.6-Ga continental growth occurred, forming the larger Laurentia (Hoffman, 1989a, b). Geologic and geochronologic studies over the past three decades have shown that most of the Precambrian in the United States south of the Hudsonian craton and west of the Grenville province (Chapter 5) consists of a broad northeast to east-northeast-trending zone of orogenic provinces that formed between 1.8 and 1.6 Ga. This zone, including extensions into eastern Canada, comprises or hosts most rock units of this age in North America as well as extensive suites of 1.35- to 1.50-Ga granite and rhyolite. This addition to the Hudsonian Craton is referred to in this chapter as the Transcontinental Proterozoic provinces (Fig. 1); the plural form is used to denote the composite nature of this broad region. 

The Transcontinental Proterozoic provinces consist of many distinct lithotectonic entities that can be defined on the basis of regional lithology, regional structure, U-Pb ages from zircons, Sr-Nd-Pb isotopic signatures, and regional geophysical anomalies.

Transcontinental Proterozoic provinces

This paper outlines the Precambrian geologic history of the continental interior of the United States by describing several selected areas from north to south. In this way the history is developed chronologically and the various areas illustrate the methods used in preparing a map of the buried basement. Lateral continental accretion is of lesser importance than is usually postulated; at least 50 percent of North America was in existence 2,500 m.y. ago. Crustal stabilization occurred at different times (about 2,500, 1,700, 1,350, and 1,000 m.y. ago) in the North American continental interior. Buried basement rocks from more than 3,000 wells and scattered outcrops in the continental interior of the United States were studied petrographically. This information, in conjunction with geophysical data and isotopic ages, was used to outline geological units and to work out the geological history. Except for the Cambrian igneous complex of the Wichita Mountains, southern Oklahoma, all basement rocks between the Rocky and Appalachian Mountains are Precambrian. Included here as basement are the widespread Precambrian sedimentary and volcanic rock sequences as well as the crystalline continental crust usually defined as basement. Rocks 2,500 m.y. old or older exposed in northern Minnesota occur as belts of west-southwest-trending granite and gneiss alternating with greenstone and schist. They extend without interruption into eastern North Dakota and northeastern South Dakota. A large part of Wyoming also is underlain by rocks at least 2,500 m.y. old. Well data for the Williston basin in eastern Montana and western North and South Dakota are too sparse to permit construction of a geologic map of the basement but isotopic ages and gravity anomalies suggest that this region is underlain by rocks deformed and consolidated about 1,700 m.y. ago during the Black Hills orogeny. The sedimentary parent rocks of the Precambrian rocks exposed in the Black Hills were deposited on an older basement that contains zircon dated at 2,550 m.y. The Black Hills are the culmination of the long north-northwest-trending basement high that includes the Chadron and Cambridge arches of Nebraska and the Central Kansas uplift. Most wells to basement have penetrated metamorphic rocks along this uplift. A granite batholith underlies the End_Page 2351------------------------------ area along the Nebraska-Kansas boundary. North of this batholith, along the uplift, isotopic ages of granite and gneiss are similar to those from the Black Hills (ca. 1,700 m.y.). The batholith intrudes mafic schist as well as the granite and gneiss; Rb-Sr ages are 1,490 m.y.; K-Ar ages of biotite from the granite batholith and schist as well as whole-rock ages of the schist are between 1,360 and 1,300 m.y. These 1,360-1,300-m.y. ages reflect a period of metamorphism or thermal activity subsequent to the original formation of the rocks but are not known to be associated with a granite-forming event here. K-Ar ages of biotite from cataclastic zones in southwestern Nebraska are 1,170 m.y. A body of anorthosite-gabbro in southwestern Nebraska has not been dated, but its cataclastic textu e and a zone of cataclasis that trends toward the body suggest that its intrusion is either contemporaneous with, or older than, the time of cataclasis. Isotopic ages in central Kansas suggest two thermal events: 1,450-1,350 m.y. and 1,250-1,100 m.y. The latter is defined on the basis of Rb-Sr and K-Ar mica ages, the former on Rb-Sr feldspar or whole-rock analyses. Granite in southeastern Nebraska, northeastern Kansas, and central Missouri is at least 1,450 m.y. old. Most of the Nemaha uplift as well as many granites at least as far west as south-central New Mexico give isotopic ages in the 1,450 to 1,350-m.y. range. During this period (the Nemaha igneous activity), rocks from New Mexico eastward to Ohio were consolidated to form the basement for younger extensive volcanic-intrusive complexes. Keweenawan basalt and associated sedimentary rock units are nearly continuous from northeastern Kansas to the outcrop belt around Lake Superior. An offset in trend and a break in continuity near the Nebraska-Kansas border have been postulated to be the result of a post-Precambrian transcontinental wrench fault. Cataclasis, recognizable in some basement samples within this discontinuity, could be associated with either rifting of the Keweenawan trough or Paleozoic movement along the adjacent north-trending Nemaha uplift. Extensive areas in southeastern Missouri, northeastern Oklahoma and vicinity, and in and near the Texas Panhandle are underlain by rhyolite and related granite. Rhyolite is found in isolated localities in Wisconsin and in some of the few basement tests in Illinois, Indiana, and Ohio. Three distinct volcanic-intrusive events can be defined: St. Francois igneous activity of southeastern Missouri (to Ohio?), 1,350-1,200 m.y. ago; Spavinaw igneous activity of northeastern Oklahoma, 1,300-1,150 m.y. ago (with a 1,200 ± 30 m.y. isochron); and Panhandle igneous activity of Texas and eastern New Mexico, 1,200-1,100 m.y. ago (1,140 ± 50 m.y. average). Each igneous event produced micrographic granite as well as rhyolite (many samples show well-preserved welded tuff textures). Rhyolite from the Spavinaw and Panhandle igneous activities covers at least 24,000 and 21,500 sq mi, respectively; the original extent of the volcanic fields is unknown. Exposed in the Llano uplift of central Texas is a thick sequence of sedimentary rocks that were deposited, folded, metamorphosed, and intruded 1,150 to 1,000 m.y. ago during the Llano orogeny. Rocks associated in time with this event are found in the subsurface of north-central Texas and Trans-Pecos Texas. Extensive areas are covered by sedimentary rocks of probable or known Precambrian age. From north to south these include: Sioux Quartzite, minimum age 1,200 m.y.; upper Keweenawan sediments in the Keweenawan trough; sediments of southwestern Missouri-southeastern Kansas; Rice Formation of Scott, central Kansas; Tillman metasedimentary group of Ham et al., southern Oklahoma and adjacent parts of Texas; De Baca terrane of this report, south-central New Mexico (possibly correlative with the Swisher diabasic terrane = Swisher gabbroic terrane of Flawn, of the Texas Panhandle); and Fisher metasedimentary terrane of Flawn, north-central Texas (probably correlative with the Llano uplift metasedimentary rocks). The last major igneous event of the central United States before the Paleozoic marine inundation was the intrusion and extrusion of the early to mid-Cambrian basalt-gabbro-rhyolite-granite igneous complex of the Wichita Mountains of southern Oklahoma. Known Precambrian rocks have yet to be penetrated by wells in the Gulf coastal plain. Crystalline basement rocks in the inner coastal plain appear to be metamorphosed Paleozoic rocks of the Ouachita system. Southward the basement is covered by thick sedimentary rocks of the Gulf Coast geosyncline.

Basement Rocks in Continental Interior of United States

The variation of 87Sr/86Sr in seawater with time can be used to determine the age of calcium sulfate beds precipitated from brine derived from seawater. The determination of a marine origin can be established by the consistency of strontium isotope results from samples at different stratigraphic levels in a single gypsum/anhydrite bed collected at separated sites. The scatter of strontium isotope results in the gypsum/anhydrite samples examined here is interpreted to result from the contribution of meteoric strontium to the salina. Strontium isotope results from three evaporite settings, the Jurassic Todilto Formation from New Mexico, the Permian Blaine Formation from Blaine County, Oklahoma, and the Permian Salado Formation from New Mexico, are used to determine the age and origin of the parent brine for these gypsum/anhydrite beds. The calcium sulfate beds from each of these formations precipitated from salinas that originated with a marine flooding but show, at different times and localities, volume do...

https://www.jstor.org/stable/10.1086/515996

Using Strontium Isotopes to Determine the Age and Origin of Gypsum and Anhydrite Beds

New geochronologic data from basement rocks support the interpretation that the Argentine Precordillera (Cuyania) terrane was rifted from the Ouachita embayment of the Iapetan margin of Laurentia. New data from the Ozark dome show a range of ages in two groups at 1466 ± 3 to 1462 ± 1 Ma and 1323 ± 2 to 1317 ± 2 Ma, consistent with existing data for the Eastern Granite-Rhyolite province and Southern Granite-Rhyolite province, respectively. Similarly, a newly determined age of 1364 ± 2 Ma for the Tishomingo Granite in the Arbuckle Mountains confirms previously published analyses for this part of the Southern Granite-Rhyolite province. Along with previously reported ages from basement olistoliths in Ordovician slope deposits in the Ouachita embayment, the data for basement ages support the interpretation that rocks of the Southern Granite-Rhyolite province form the margin of Laurentian crust around the corner of the Ouachita embayment, which is bounded by the Ouachita rift and Alabama-Oklahoma transform fault. In contrast, both west and east of the corner of the Ouachita embayment, Grenville-Llano basement (approximately 1325–1000 Ma) forms the rifted margin of Laurentia. New U/Pb zircon data from basement rocks in the southern part of the Argentine Precordillera indicate crystallization ages of 1205 ± 1 Ma and 1204 ± 2 Ma, consistent with previously reported ages (approximately 1250–1000 Ma) of basement rocks from other parts of the Precordillera. These data document multiple events within the same time span as multiple events in the Grenville orogeny in eastern Laurentia, and are consistent with Grenville-age rocks along the conjugate margins of the Precordillera and Laurentia. Ages from one newly analyzed collection, however, are older than those from other basement rocks in the Precordillera. These ages, from granodioritic-granitic basement clasts in a conglomerate olistolith in Ordovician slope deposits, are 1370 ± 2 Ma and 1367 ± 5 Ma. These older ages from the Precordillera are consistent with indications that the Iapetan margin in the Ouachita embayment of Laurentia truncated the Grenville front and left older rocks of the Southern Granite-Rhyolite province (1390–1320 Ma) at the rifted margin. Chronostratigraphic correlations of synrift and post-rift sedimentary deposits on the Precordillera and on the Texas promontory of Laurentia document initial rifting in the Early Cambrian. Previously published data from synrift plutonic and volcanic rocks in the Wichita and Arbuckle Mountains along the transform-parallel intracratonic Southern Oklahoma fault system inboard from the Ouachita embayment document crystallization ages of 539–530 Ma. New data from synrift volcanic rocks in the Arbuckle Mountains in the eastern part of the Southern Oklahoma fault system yield ages of 539 ± 5 Ma and 536 ± 5 Ma, confirming the age of synrift volcanism.

Ages of pre-rift basement and synrift rocks along the conjugate rift and transform margins of the Argentine Precordillera and Laurentia

The Upper Permian (lower Ochoan) Castile Formation is a major evaporite sequence (10,000 km3) of calcite, anhydrite, and halite in west Texas and southeastern New Mexico. Traditionally the Castile brine has been considered to have been derived from seawater. This tradition has recently been challenged by two versions of the closed-basin drawdown model. They call for deposition from a mixed brine, in part marine and in large part nonmarine. They propose drawdown of as much as 500 m to form a major sink for ground water issuing from the surrounding Capitan reef complex. A large fraction of the solute in the brine body is inferred to have been recycled from older Permian evaporites on the surrounding shelf. Strontium-isotope analyses show no evidence that meteoric ground water was contributed to the Castile brine. From a stratigraphic, geographic, and lithologic array of 65 samples of anhydrite, gypsum, and calcite, 59 have an 87Sr/86Sr ratio of 0.706923 (sw of -225.0), a ratio that is the same as that of strontium in early Ochoan ocean water. If considerable (>15%) influx of meteoric water had occurred, enough continental strontium would have been introduced to have resulted in higher ratios. Low bromide values (20-40 ppm) in Castile halite, which have been used to argue for meteoric influx and for recycled salt, probably resulted from diagenesis. During shallow burial by halite, centimeter-size, bottom-grown crystals of gypsum were altered to nodular anhydrite. The rising water of dehydration caused the halite to recrystallize. During the recrystallization, some bromide was expelled. Despite the large volume of water that evaporated annually from its surface (52 km3/yr, assuming an evaporation rate of 2 m/yr), the Castile brine body never completely desiccated. The surrounding shelf was flat, hot, and generally dry. It probably could not have supplied a significant volume of meteoric spring water to the basin over tens of thousands of years. More likely, during the entire history of the evaporite sequence, influx was dominantly marine. Marine ground water flowed through the Capitan Formation into the evaporite basin along its southern and possibly western margin probably with a rate of flow that was usually fast enough to prevent major drawdown of the brine surface.

/pdf/parent-brine-of-the-castile-evaporites-upper-permian-texas-455ktyhqci.pdf

Rodger E. Denison

Papers

Transcontinental Proterozoic provinces

Basement Rocks in Continental Interior of United States

Using Strontium Isotopes to Determine the Age and Origin of Gypsum and Anhydrite Beds

Ages of pre-rift basement and synrift rocks along the conjugate rift and transform margins of the Argentine Precordillera and Laurentia

Parent Brine of the Castile Evaporites (Upper Permian), Texas and New Mexico