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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 37 records · Page 2Linked to original sources
USGS2011

A feasibility study of geological CO2 sequestration in the Ordos Basin, China

The Shaanxi Province/Wyoming CCS Partnership (supported by DOE NETL) aims to store commercial quantities of CO2 safely and permanently in the Ordovician Majiagou Formation in the northern Ordos Basin, Shaanxi Province, China. This objective is imperative because at present, six coal-to-liquid facilities in Shaanxi Province are capturing and venting significant quantities of CO2. The Wyoming State Geological Survey and the Shaanxi Provincial Institute of Energy Resource and Chemical Engineering conducted a feasibility study to determine the potential for geological CO2 sequestration in the northern Ordos Basin near Yulin. The Shaanbei Slope of the Ordos Basin is a huge monoclinal structure with a high-priority sequestration reservoir (Majiagou Formation) that lies beneath a 2,000+ meter-thick sequence of Mesozoic rocks containing a multitude of lowpermeability lithologies. The targeted Ordovician Majiagou Formation in the location of interest is more than 700 meters thick. The carbonate reservoir is located at depths where pressures and temperatures are well above the supercritical point of CO2. The targeted reservoir contains high-salinity brines (20,000-50,000 ppm) that have little or no economic value. The targeted reservoir is continuous as inferred from well logs, and cores show that porosity ranges from 1 to 15% with average measured porosity of 8%, and that permeability ranges from 1-35 md. This paper focuses on calculations that will help evaluate the capacity estimates through the use of high-resolution multiphase numerical simulation models, as well as a more simple volumetric approach. The preliminary simulation results show that the Ordovician Majiagou Formation in the Ordos Basin has excellent potential for geological CO2 sequestration and could store the CO2 currently emitted by coal-to-liquid facilities in Shaanxi Province for hundreds of years (i.e., 9 Mt/year CO2; 450 Mt over a 50-year period at one injection site). ?? 2011 Published by Elsevier Ltd.

Conference Paper↗
USGS2009

Validation of the rupture properties of the 2001 Kunlun, China (Ms = 8.1), earthquake from seismological and geological observations

We determine the finite-fault slip distribution of the 2001 Kunlun earthquake ( M s = 8.1) by inverting teleseismic waveforms, as constrained by geological and remote sensing field observations. The spatial slip distribution along the 400-km-long fault was divided into five segments in accordance with geological observations. Forward modelling of regional surface waves was performed to estimate the variation of the speed of rupture propagation during faulting. For our modelling, the regional 1-D velocity structure was carefully constructed for each of six regional seismic stations using three events with magnitudes of 5.1–5.4 distributed along the ruptured portion of the Kunlun fault. Our result shows that the average rupture velocity is about 3.6 km s −1 , consistent with teleseismic long period wave modelling. The initial rupture was almost purely strike-slip with a rupture velocity of 1.9 km s −1 , increasing to 3.5 km s −1 in the second fault segment, and reaching a rupture velocity of about 6 km s −1 in the third segment and the fourth segment, where the maximum surface offset, with a broad fault zone, was observed. The rupture velocity decelerated to a value of 3.3 km s −1 in the fifth and final segment. Coseismic slip on the fault was concentrated between the surface and a depth of about 10 km. We infer that significant variations in rupture velocity and the observed fault segmentation are indicative of variations in strength along the interface of the Kunlun fault, as well as variations in fault geometry.

Qinghai Province↗
USGS2008

Rapid exposure and loss estimates for the May 12, 2008 Mw 7.9 Wenchuan earthquake provided by the U.S. Geological Survey's PAGER system

One half-hour after the May 12th Mw 7.9 Wenchuan, China earthquake, the U.S. Geological Survey’s Prompt Assessment of Global Earthquakes for Response (PAGER) system distributed an automatically generated alert stating that 1.2 million people were exposed to severe-to-extreme shaking (Modified Mercalli Intensity VIII or greater). It was immediately clear that a large-scale disaster had occurred. These alerts were widely distributed and referenced by the major media outlets and used by governments, scientific, and relief agencies to guide their responses. The PAGER alerts and Web pages included predictive ShakeMaps showing estimates of ground shaking, maps of population density, and a list of estimated intensities at impacted cities. Manual, revised alerts were issued in the following hours that included the dimensions of the fault rupture. Within a half-day, PAGER’s estimates of the population exposed to strong shaking levels stabilized at 5.2 million people. A coordinated research effort is underway to extend PAGER’s capability to include estimates of the number of casualties. We are pursuing loss models that will allow PAGER the flexibility to use detailed inventory and engineering results in regions where these data are available while also calculating loss estimates in regions where little is known about the type and strength of the built infrastructure. Prototype PAGER fatality estimates are currently implemented and can be manually triggered. In the hours following the Wenchuan earthquake, these models predicted fatalities in the tens of thousands.

Wenchua↗
USGS2025

A time-space model of graphite mineral systems

Increasing demand for graphite in energy storage systems warrants review of graphite ore genesis in a mineral systems framework. Orogenic graphite encompasses the metamorphic and orogenic mineral systems that produce flake graphite and hydrothermal vein (lump and chip) graphite deposits, respectively. A common feature of orogenic graphite deposits is an association with upper amphibolite- to granulite-facies metasedimentary rocks in continent-continent or continent-island arc collisional orogens. Orogenic flake graphite deposits form primarily through graphitization of organic carbon during regional metamorphism, but strain localization and partial melting of pelitic protoliths are likely important processes for graphite grade and quality enrichment. Orogenic vein graphite deposits precipitate from hydrothermal fluids, possibly derived from metamorphism or anatexis at depth. Decarbonation reactions in mixed calcareous-carbonaceous metasedimentary sequences are the most likely carbon sources for the veins. In contrast, intrusion-related graphite includes magmatic-hydrothermal and metamorphic mineral systems that form primarily in continental arc settings via the interaction of magmas with carbonaceous sedimentary packages. Magmatic-hydrothermal flake graphite deposits are hosted in plutonic and volcanic rocks, and result from the exsolution of CO 2 -CH 4 -rich fluids from melts contaminated by such packages. Contact metamorphism of carbonaceous sedimentary rocks by plutons produces some microcrystalline (amorphous) graphite deposits, including many in China. Compilation of geologic data from known graphite deposits globally suggests that pulses of carbon deposition in the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic provided source carbon material. Subsequent supercontinent orogenesis at ca. 2,100 to 1,700 Ma (Columbia), ca. 1,300 to 1,000 Ma (Rodinia), and ca. 650 to 500 Ma (Gondwana) resulted in the genesis of orogenic flake and vein graphite deposits, where favorable geologic components overlapped with organic ± carbonate carbon-rich strata. Cryogenian deposition of graphite protoliths and Cryogenian – Cambrian metamorphic mineralization account for nearly 75% of all known resources globally and coincide with profound carbon isotope excursions and climate variability, implying a link with the global carbon budget. Comparatively few graphite deposits are associated with Pangea-forming orogens, attributed to less exhumation and/or denudation. High-temperature metasedimentary belts containing organic carbon-rich protoliths are most favorable for hosting orogenic flake graphite deposits, whereas sequences that also contain carbonate protoliths are favorable for orogenic graphite veins. Continent-scale orogenic belts may host both deposit types along with vanadium deposits. Use of a time-space mineral systems framework for graphite deposits can improve exploration models needed to ensure future supply of this critical mineral and provide insights into Earth’s long-term carbon cycle.

Mineralium Deposita↗
USGS2009

High-frequency Rayleigh-wave method

High-frequency (≥2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor ( Q ), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q ) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution.

Earth Science↗
USGS2010

Detrital zircon provenance from three turbidite depocenters of the Middle-Upper Triassic Songpan-Ganzi complex, central China: Record of collisional tectonics, erosional exhumation, and sediment production

To test the idea that the voluminous upper Middle to Upper Triassic turbidite strata in the Songpan-Ganzi complex of central China archive a detrital record of Dabie ultrahigh-pressure (UHP) terrane unroofing, we report 2080 single detrital U-Pb zircon ages by sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis from 29 eastern Songpan-Ganzi complex sandstone samples. Low (<0.07) Th/U zircons, consistent with crystallization under UHP conditions, are rare in eastern Songpan-Ganzi complex zircon, and U-Pb ages of low Th/U zircons are incompatible with a Dabie terrane source. An unweighted pair group method with arithmetic mean nearest-neighbor analysis of Kolmogorov-Smirnov two-sample test results reveals that the eastern Songpan-Ganzi complex is not a single contiguous turbidite system but is instead composed of three subsidiary depocenters, each associated with distinct sediment sources. The northeastern depocenter contains zircon ages characterized by Paleozoic and bimodally distributed Precambrian zircon populations, which, together with south-to southeast-directed paleocurrent data, indicate derivation from the retro-side of the Qinling-Dabie (Q-D) collisional orogen wedge. In the central depocenter, the dominantly Paleozoic detrital zircon signature and south-to southwest-oriented paleocurrent indicators reflect a profusion of Paleozoic zircon grains. These data are interpreted to reflect an influx of material derived from erosion of Paleozoic supra-UHP rocks of the Dabie terrane in the eastern Qinling-Dabie orogen, which we speculate may have been enhanced by development of a monsoonal climate. This suggests that erosional unroofing played a significant role in the initial phase of UHP exhumation and likely influenced the petrotectonic and structural evolution of the Qinling-Dabie orogen, as evidenced by compressed Triassic isotherms/grads reported in the Huwan shear zone that bounds the Dabie terrane to the north. The central depocenter deposits reflect a later influx of bimodally distributed Precambrian zircon, signifying either a decrease in the influx of Paleozoic zircon grains due to stalled UHP exhumation and/or dilution of the same influx of Paleozoic zircons by spilling of Precambrian zircon from the northeastern depocenter into the central depocenter basin, perhaps due to infilling and bypass of sediment from the northern depocenter or due to initial collapse and constriction of the eastern Songpan-Ganzi complex basin. The southeastern depocenter of the eastern Songpan-Ganzi complex bears significant Paleozoic, Neoproterozoic, and Paleoproterozoic zircon populations derived from the South China block and Yidun arc complex, likely recording nascent uplift of the Longmenshan deformation belt due to impingement of the Yidun arc complex upon the western margin of the South China block. ?? 2010 Geological Society of America.

Geological Society of America Bulletin↗
USGS1999

Geology of the Loess Hills, Iowa

Many Americans think of Iowa as having little topographic variation. However, in westernmost Iowa the Loess Hills rise 200 feet above the flat plains forming a narrow band running north-south 200 miles along the Missouri River. The steep angles and sharp bluffs on the western side of the Loess Hills are in sharp contrast to the flat rectangular cropfields of the Missouri River flood plain. From the east, gently rolling hills blend into steep ridges. Loess (pronounced "luss"), is German for loose or crumbly. It is a gritty, lightweight, porous material composed of tightly packed grains of quartz, feldspar, mica, and other minerals. Loess is the source of most of our Nation's rich agricultural soils and is common in the U.S. and around the world. However, Iowa's Loess Hills are unusual because the layers of loess are extraordinarily thick, as much as 200 feet in some places. The extreme thickness of the loess layers and the intricately carved terrain of the Loess Hills make them a rare geologic feature. Shaanxi, China, is the only other location where loess layers are as deep and extensive. Though much older (2.5 million years) and much thicker (nearly 300 feet) than Iowa's loess, the Shaanxi loess hills have been greatly altered by both natural and human activity and no longer retain their original characteristics.

Iowa↗
USGS1990

The Bayan Obo iron-rare-earth-niobium deposits, Inner Mongolia, China

The plate tectonic setting, regional geology and certain aspects of the economic geology of the iron-rare-earth-niobium ore bodies at Bayan Obo, Inner Mongolia, China, were studied by a team of geologists from the Tianjin Geologic Research Academy and the U.S. Geological Survey between 1987 and 1989. These ore bodies were formed by hydrothermal replacement of Middle Proterozoic dolomite in an intra-continental rift setting. A variety of veins and/or dikes that have a carbonatitelike mineralogy cut the footwall clastic rocks and migmatites. A stockwork of veins occurs at several locations in the footwall. The hanging wall is a shale that has been converted to a K-metasomatite and has microcrystalline potassium feldspar as its principal constituent. This shale served as a sealing caprock that contained the chemical solutions that reacted with the dolomite and created the enormous concentration of mineralized rock in an 18-kilometer-long syncline. The rocks that host these ore bodies and the associated mineralized areas occur today as roof pendants in granitoid rocks of Permian age that were emplaced during a continent-to-continent collision during that period.

LITHOS↗