Browsing by Subject "Petrology"
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item Basement rocks in adjoining parts of Oklahoma, Kansas, Missouri, and Arkansas(1966-08) Denison, Rodger E.; Muehlberger, William R.Samples from more than two hundred and twenty wells penetrating basement rock have been examined and described from a 61,000 square mile area in adjoining parts of Oklahoma, Kansas, Missouri, and Arkansas. Twenty-five isotopic age determinations were made on twenty samples of basement rock from wells and outcrop areas. Nine basement rock units can be defined within the study area on the basis of petrography and isotopic age. 1. "Older granite and gneiss" is a loose association of granitic rocks considered to be older than 1400 million years. The unit cannot be precisely defined within the study area. 2. The Lyon County Quartzite is a micaceous quartzite restricted to relatively small areas in the buried basement of Kansas. The age of deposition is unknown but preceded the 1400 million year age of metamorphism. 3. The Chase County Granite Group is composed largely of granite and gneissic granite. Rocks of this group underlie most of the Nemaha Uplift in Kansas and also occur considerably east and west of the Uplift. The rocks were intruded at about 1400 million years, probably as a composite batholith. At about 1200 million years, four petrographically related rock units were intruded or extruded. The age difference between these units cannot be distinguished by isotopic ages. The four units are assembled into the Northeast Oklahoma Province, a petrographic grouping of volcanic rocks and chemically equivalent hypersolvus type epizone granites. 4. The Washington County Volcanic Group is composed mostly of rhyolite but also contains andesite and metarhyolite. The majority of the rhyolites were probably extruded as welded tuffs. 5. The Spavinaw Granite Group is composed of generally micrographic granite porphyries. The intrusions are considered to be largely sills on textural evidence and by analogy with outcrop areas elsewhere. 6. The Woodson County Granite is texturally variable. Samples from drill holes in Kansas are petrographically identical to boulders found at Rose Dome in Woodson County, Kansas. 7. The Osage County Microgranite is the most uniform unit in the area. The microgranite occurs in a roughly circular area in Osage County, Oklahoma. The unit was probably intruded as a sill within rhyolite flows. Two other petrographic units are interpreted as being younger than parts of the Northeast Oklahoma Province, although in the same 1200 million years isotopic age range. 8. The Vernon County Metamorphic Group is composed mostly of low rank metamorphic rocks derived from clastic sediments. The grade of metamorphism is from incipient to middle greenschist facies. Rhyolite detritus occurs in some samples. 9. The Central Oklahoma Granite Group is composed of two feldspar mesozone type granites. The unit is not distinguishable from the Chase County Granite Group on the basis of petrography. Uplift and erosion followed the intrusion of the Central Oklahoma Granite Group. The main uplifts were along the present Nemaha Uplift and along a northeast-southwest axis from southwest Missouri to central Oklahoma. There is no evidence for any igneous or metamorphic activity between 1200 million years and the deposition of lower Paleozoic sediments.Item Crustal xenoliths from Potrillo Maar: implications for evolution of continental crust beneath the southern Rio Grande rift(Texas Tech University, 2003-08) Chattopadhyay, IndraniThe mid-crustal xenoliths from Potrillo maar record a petrologic and geochemical history that has until now been unknown from the Potrillo volcanic field. The igneous and meta-igneous xenoliths are samples of one or more plutonic bodies that crystallized at depths from 7-14 km (middle to upper crust). The rock unit ranges in composition from hornblende biotite diorite to quartz monzonite and monzogranite; it is broadly alkalicalcic The initial Sr87Sr86 suggests that the source region is heterogeneous or that the parental magmas were contaminated by crustal material. At least three geochemical groups can be identified, primarily on the basis of silica content. There is considerable overlap between groups 1 and 2, and the boundary between these two groups cannot be distinguished graphically. The third group is granitic and is geochemically distinct from groups 1 and 2. A dioritic composition is thought to represent mafic parental magma. Its calculated liquidus temperature at 2% H2O and 4 Mpa pressure is 1172°C. The presence of fossiliferous limestone xenoliths indicates that the Potrillo maar eruption sampled rocks of late Paleozoic age. However, the age of marble and quartzite xenoliths are not known. The quartzite xenoliths are relatively undeformed, but isoclinal folding in some of the marble xenoliths suggests subsurface deformation that has not been observed in local surface exposures of metasedimentary rocks. One model proposed for the crust under the southern Rio Grande rift assumes that the marble is late Paleozoic in age. The fossiliferous limestones are late Paleozoic in age and are older than the plutonic rocks. The relative age of the deformed marbles in this model is not clear, it can be deformed with the plutonic rocks or due to an earlier regional extensional event. In the second model, marble is proposed to result from contact metamorphism in the aureole of a plutonic rock body at a depth of 7-14 km. The presence of marble and calc-silicate xenoliths in dioritic blocks is consistent with a correlation of the marble with surface exposures of the Castner Marble in the Franklin MountainsItem Deposition, diagenesis and distribution of an "Upper Silurian" dolostone reservoir, RK Devonian Field(Texas Tech University, 1984-12) Young, Joe BrianThe RK Devonian Field was discovered in May 1975 with the completion of RK Petroleum Corporation's #1 G.T. Hall for an initial flowing potential of 455 BOPD on a 7/64" choke with a flowing tubing pressure of 1018#'s from five feet of perforations from 11,810-15' after treating with 250 gallons of acid. The well is located 660 feet from the north and west lines of Section 4, T&P RR. Co. Survey, Township 2-N, Block 37, Martin County, Texas. The field is situated in central Martin County (Fig. 1) approximately three miles north of the village of Tarzan and now includes all or parts of the following surveys and blocks: T&P RR. Survey, Township 2-N, Block 37, R.E. Montgomery Survey, Block A.Item Geology and petrology of Cretaceous and Tertiary granitic rocks, Lamoille Canyon, Ruby Mountains, Nevada(Texas Tech University, 1999-05) Lee, Sang-YunLamoille Canyon cuts through the northern Ruby Mountain metamorphic core complex and exposes the deep interior, which is characterized by highly metamorphosed miogeoclinal sedimentary rocks and various late Cretaceous and Tertiary granitic intrusions. Late Cretaceous granitic rocks in Lamoille Canyon can be broadly divided into two groups based on field relations: equigranular two-mica granitic gneiss and pegmatitic sillimanite-bearing two-mica granitic gneiss. The former rock unit is distinct in its higher concentrations of Fe, Mg, Na, Ca, Sr, V, Zr, Zn, Hf, but lower K, Rb, Th. In spite of these elemental differences, both of the late Cretaceous granitic units in this region are strongly peraluminous, have similar S^18 values, and are closely associated in the field. The origin of the pegmatitic two-mica granitic gneiss is best modeled by muscovite dominated dehydration melting of a metapelitic source, whereas the equigranular twomica granitic gneiss formed by plagioclase-imited biotite dehydration melting of a metapelitic source. Oligocene biotite monzogranite and related tonalitic dikes were emplaced in middle crustal levels (5-6 kbar). The biotite monzogranite suite consists of three geochemically distinct sub-groups. Group I shows characteristic geochemical features of A-type granite and is likely to have been generated by reaction of mantle-derived basaltic magma with either Archean orthogneiss or Proterozoic metapelite, leaving abundant plagioclase, orthopyroxene, and clinopyroxene as cumulative phases. Compared to group I, group II lacks characteristics of A-type granite. Partial melting of a metapelitic source explains most of the observed geochemical and stable isotopic data of group II. Geochemical variations within group I and group II can be explained by fractional crystallization but the possibility of minor crustal assimilation cannot be excluded. The compositions of tonalitic dikes are best explained by magma mixing between mantle derived (?) basaltic magma and granitic magma of the biotite monzogranite suite. Systematic geochemical comparison between the late Cretaceous and Oligocene granitic intrusions suggests temporal transition from early deep-seated crustal anatexis of a garnet-bearing source in a thickened crust, to later interaction between mantle-derived magma and crust, or high-temperature biotite-dehydration melting in a shallower crustal environment.Item Integrated stratigraphy and petrology of the Silurian Wink formation (Wenlock-Ludlow) Howard County, Texas(Texas Tech University, 2004-05) Kohl, Michael LThe Cobra-Frazier #1 well in Howard County penetrated the Silurian Wristen Group and Fusselman Formation, and a core with sixty feet of strata was recovered, the majority of which belongs to the Wink Formation of the Wristen Group. Petrologic, petrographic, and geochemical studies allow interpretation of the depositional and diagenetic history of the Wink Formation in the eastern margin of the Permian Basin region. The Wink of the Cobra-Frazier #1 consists of argillaceous skeletal wackestones and mudstones that are dominated by a deep water fauna dominated by arthropods. Conodont faunas indicate that the age of the Wink ranges from the early Sheinwoodian (Wenlock), into the Gorstian (Ludlow) and perhaps as young as the early Ludfordian. The Wink Formation was deposited when the exposed Fusselman platform was flooded in the early Sheinwoodian. Deposition continued in a carbonate ramp setting until differential subsidence produced the platform and basin fades of the Fasken and Frame formations. During the hiatus that separated the Thirtyone Formation from the Woodford Formation, the Wink was karsted, evidenced by the presence of crackle, mosaic, and chaotic breccia fabrics related to paleocave formation and collapse. The karst-related porosity was subsequently filled by fine-grained argillaceous carbonate sediments. After the karsting event, the Wink strata underwent to three dolomitization events, two diagenetic, and one epithermal event related to the Ouachita Orogeny. The two diagenetic dolomitization events did not affect the entire Wink equally, with increased dolomitization in the lower portion of the core. In the lower Wink, this created a dolostone with intercrystalline, vuggy, and fracture porosity. Subsequent precipitation of baroque dolomite, from the epithermal event, and calcite cements destroyed much of the porosity throughout the core. Analysis of carbon and oxygen stable isotopes produced curves that were used to test models of oceanic and environmental cyclicity. When compared to oceanic and environmental models, the data was inconclusive, neither clearly supporting nor refuting any of the models. Two positive excursions associated with the Mulde Event and near the Wenlock-Ludlow Boundary are present in both the carbon and oxygen curves. These excursions have carbon §-values increased by slightly more than l%o, and the oxygen 5-values increases of more than 2%o. The excursions allow correlations between the Wink and strata in Oklahoma, Nevada, and across many parts of Europe, particularly the Baltic region.Item Lower Pennsylvanian stratigraphy of the Central Colorado Trough(Texas Tech University, 2003-08) Musgrave, Bryan EdwardThe Central Colorado Trough formed as a result of the uplift of the Ancestral Rocky Mountains. With uplift, sediments were eroded from the adjacent highlands and deposited in the trough. The Lower Pennsylvanian stratigraphy of the Central Colorado Trough was determined based on outcrops in the southern Mosquito Range and Arkansas River Valley east of Salida, Colorado. The Kerber Formation is the oldest Pennsylvanian strata in the Central Colorado Trough and was derived from the erosion of older Paleozoic sedimentary rocks and some crystalline basement rocks. It was deposited in alluvial fan and braided streams environments near the edges of the trough. Along the axial portion of the Trough, it was deposited in braid-delta and shallow marine environments. As marine incursion occurred from the northwest, a retrogradational sequence developed. Based on conodont faunas, the upper Kerber Formation is late Morrowan to Atokan in age. Because the strata of the Central Colorado Trough are intimately related to the initial uplift of the Ancestral Rocky Mountains, the formation of the Ancestral Rocky Mountains began no later than the late Morrowan. The Kerber Formation correlates with the Belden Formation of the northern portion of the Trough based on the first appearance of the conodonts Idiognathoides sinuatus, Idiognathodus sinuosus, and Idiognathodus parvus. At Willard Springs they occur within the Belden, whereas they occur within the Kerber at Wells Gulch, 8 km to the south. The dark marine sediments of the Belden Formation extend further southward than previously documented, and approximately 127 m of section occurs at Willard Springs, northeast of Salida. At Willard Springs, the Belden Formation lies conformably above the Kerber Formation and conformably below the Sharpsdale Formation. This is the first time that the Belden has been documented m contact with the Sharpsdale Formation. At Wells Gulch and Box Canyon to the south, the Belden Formation grades into shallow-water carbonates and shales interbedded with Kerberand Sharpsdale-type elastics. The Sharpsdale Formation was derived from the erosion of Precambrian crystalline basement rocks of the Uncompahgre Highland as the climate of the Pennsylvanian grew more arid. It was deposited in alluvial fan and braided stream environments near the edges of the trough. Along the axial portion of the trough, it was deposited in braid-delta and rare shallow marine environments. A northward prograding sequence developed as sediment influx exceeded local sea-level rise.Item Paradox Basin source rock, southeastern Utah : organic geochemical characterization of Gothic and Chimney Rock units, Ismay and Desert Creek zones, within a sequence stratigraphic framework(1995-08) Tischler, Keith Louris; Kirkland, Brenda Lee, 1959-The Chimney Rock and Gothic units of the Pennsylvanian Paradox Formation have long been considered source rocks for the rich hydrocarbon fields of southeastern Utah. Fundamental questions about these units include: source and nature of the organic material, source rock character, and position of the source rocks in the existing sequence stratigraphic framework. The Chimney Rock and Gothic, historically referred to as shales, are composed of calcareous mudstone, dolomudstone, and calcareous sandstone. High total organic carbon (TOC) values are more closely linked to sequence stratigraphic position than lithology. In the Gothic, TOC values decrease upwards. Terrestrial maceral content increases upwards in both the Gothic and the Chimney Rock as determined through point-count and qualitative observation. Pyrolysis indicates that greater than anticipated terrestrial influence is present and is consistent for all wells. No distinct difference in geochemical character exists between the two units. Sequence stratigraphic boundaries appear to be as good as, or better, than traditional lithostratigraphic boundaries for determining high TOC occurrence and source rock location. Within repetitive major sea level transgressions the organic matter that fed the basin evolved from a marine-dominated signature to a terrestrial-dominated signature.Item Petrography of the middle and upper Holder Formation (Upper Pennsylvanian), Sacramento Mountains, New Mexico(Texas Tech University, 1985-12) Yocum, Eric T.The middle and upper Holder formation (Upper Pennsylvanian), Sacramento Mountains, New Mexico, comprises terrigenous and carbonate facies that accumulated on a narrow open to restricted marine shelf. Differential subsidence of the shelf combined with eustatic sea level changes caused cyclic deposition. Deposition began with a varying supply of terrigenous sediments frcm shifting delta lobes. Several carbonate facies, lateral equivalents of the terrigenous strata, are distinguished on the basis of their allochemical constituents. Bioclastic wackestones to grainstones with cortoids and oncoids characterize open marine intervals. Fusulinids , algal , and peloidal grainstones were common marginal-marine facies. Laminoid fenestral mudstones and wackestones with oncoids were common in restricted marine intervals. Restricted marine sediments were deposited after clastic influxes and during marine transgressions.Item Spatial distribution of zircons in porphyroblastic gneisses(Texas Tech University, 1976-05) Meers, Ronald BNot availableItem Subsurface investigation of the Pennsylvanian cross cut sandstone, TWP and Busher fields, Runnels County, Texas(Texas Tech University, 1995-05) Henderson, Steven KirkThe Upper Pennsylvanian (Missourian) Cross Cut sandstone of the TWP and Busher fields. Runnels County, Texas, is an example of the smaller hydrocarbon plays that are receiving increased attention in west- and north-central Texas. An understanding of the distributions and reservoir characteristics of these plays is necessary for ensuring the success of future exploration and development strategies. Sediment characteristics, petrophysical log responses, and sand body geometry of the TWP and Busher Cross Cut sandstone reflect deposition in a distal prograding delta environment. Gross sand isopach mapping reveals a strikeoriented sand body approximately three miles in length and one-half mile in width. These attributes are similar to characteristics of the Cross Cut sandstone in other Pennsylvanian fields, and support a delta-front interpretation. Delta-front sandstones of the TWP and Busher fields represent a southwestern distal extension of the Eastland Delta system. Log responses and sand body geometry may be employed to infer the position of distributary mouth bar and channel facies associated with the delta-front sands. Sediments of the Cross Cut sandstone were exposed to a variety of diagenetic processes that influenced the evolution and preservation of porosity and permeability within the reservoir. Early development of epitaxial quartz overgrowths significantly decreased depositional porosity. Replacive calcite may also have decreased primary porosity; however, the dissolution of this calcite produced minor amounts of secondary porosity. Late-stage diagenetic processes, including precipitation of kaolinite and ankerite cements, further occluded porosity. The types, abundances, and morphologies of clay minerals, especially kaolinite and chlorite, within the Cross Cut sandstone may influence reservoir quality, in addition to reducing initial reservoir porosity and permeability. Interaction of these clays with fluids introduced during drilling, completion, and production may cause dispersion and migration of fines and precipitation of insoluble compounds, further occluding effective porosity and decreasing permeability. Petrophysical and volumetric evaluation of the TWP and Busher Cross Cut reservoir reveals estimated recoverable reserves of 763,997 stock tank barrels of oil. Since the discovery of the Busher Field in 1956, both fields haveproduced a combined total of approximately 629,667 barrels of oil. The Cross Cut sandstone within the TWP and Busher fields is an essentially depleted reservoir.Item The petrology and geochemistry of the english peak intrusive suite, Klamath mountains, California(Texas Tech University, 1994-12) Schmidt, Bennetta L.The English Peak intrusive suite is a calcic to calc-alkaline late middle Jurassic composite pluton located in the central Klamath Mountains of northern California. The suite consists of the Uncles Creek, Heiney Bar, and English Peak plutons. This study was designed to sample the intrusive suite, to determine the mineralogy and rock types of the plutons, to measure the geochemical variation of the plutonic units in the suite, and to establish which magmatic processes were responsible for the chemical variation. Geochemical analysis revealed that the English Peak intrusive suite was emplaced in at least eight pulses of magma at temperatures in the range 1000 to 1150^ C and a depth of approximately 11 km. The plutonic imits were intruded in the order: Uncles Creek pluton; Heiney Bar pluton; English Peak pluton early stage; English Peak pluton intermediate stage; and English Peak pluton late stage, which is composed of three compositional groups. Trace element compositions indicate the magmas were derived from subduction-modified mantle or subduction derived crust. Initial Sr/ Sr ratios of 0.7038 to 0.7045 are compatible with mantle-derived magmas; however, limited 5^^0 values for quartz separates of approximately +13.5 ^/oo require a high 5^^0 crustal component in the magmas. Water content of the magmas was variable. In the English Peak pluton, with the exception of the extreme southeastern margin, the magmas in the early stage were apparently drier than the in late stage. Geochemical modeling of the late stage of the English Peak pluton suggest an origin by fi'actional crystallization of a parental magma of intermediate composition accompanied by injection and mixing of mafic magmas.Item The petrology and tectonics of the mesoproterozoic margin of southern Laurentia(Texas Tech University, 2001-05) Barnes, Melanie A. W.During the evolution of Laurentia, a Mesoproterozoic granite-rhyolite belt extended from Finland through Canada to the southwestern United States. This graniterhyolite province forms much of tiie west Texas and eastern New Mexico basement, where it is known locally as the Panhandle tertane and underiies the Debaca tertane (a metasedimentary and metavolcanic unit intruded by gabbro). The first study is a regional geological investigation of the Panhandle tertane using subsurface samples. The second study presents data from 41 closely spaced wells which penetrated several hundred meters into basement, providing the first opportunity to develop a 3-D view of the Panhandle terrane. Geochemical and isotopic data are presented for the Panhandle terrane, Debaca terrane, and deformed 'crystalline terrane' which consists of felsic intrusive rocks of unknown affinity. Characterization of the Panhandle terrane felsic rocks revealed three main groups: (1) early quartz monzonite and granite (-1.38 Ga), (2) a granite-rhyolite association (-1.36 Ga), and (3) late quartz syenite (-1.34 Ga). In addition, there are mafic rocks, the majority of which are thick sills intruding the granite-rhyolite pile. These sills have an alkaline, OIB-like signature, and Nd model ages imply they are contemporaneous with the felsic rocks. A neodymium model age for a Debaca terrane gabbro (1.26 Ga) is distinctly younger than a Panhandle terrane gabbro, as are Nd model ages (1.35 to 1.47 Ga) for the crystalline terrane granites, indicating that both tertanes are distinct from the granite-rhyolite province. In addition, a meta-arkose of the Debaca tertane containing detrital zircons (1.69 and 1.32 Ga) uncomfortably overlies a Panhandle terrane quartz syenite (1.33 Ga), suggesting derivation of the Debaca sediments from older terranes. The most significant petrologic features for understanding the tectonic regime are (1) the bimodal nature of the suite, (2) the alkaline character of both the mafic and felsic samples, and (3) evidence from Nd isotopes that the felsic magmatism is crustal. These features indicate that there was not subduction during this time period and instead agree with previous models where decompression melting of the mantle results in large volumes of mafic magmas which trigger extensive crustal anatexis.