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At least 343 records · Page 19Linked to original sources
USGS2013

Linking geology and health sciences to assess childhood lead poisoning from artisanal gold mining in Nigeria

Background: In 2010, Médecins Sans Frontières discovered a lead poisoning outbreak linked to artisanal gold processing in northwestern Nigeria. The outbreak has killed approximately 400 young children and affected thousands more. Objectives: Our aim was to undertake an interdisciplinary geological- and health-science assessment to clarify lead sources and exposure pathways, identify additional toxicants of concern and populations at risk, and examine potential for similar lead poisoning globally. Methods: We applied diverse analytical methods to ore samples, soil and sweep samples from villages and family compounds, and plant foodstuff samples. Results: Natural weathering of lead-rich gold ores before mining formed abundant, highly gastric-bioaccessible lead carbonates. The same fingerprint of lead minerals found in all sample types confirms that ore processing caused extreme contamination, with up to 185,000 ppm lead in soils/sweep samples and up to 145 ppm lead in plant foodstuffs. Incidental ingestion of soils via hand-to-mouth transmission and of dusts cleared from the respiratory tract is the dominant exposure pathway. Consumption of water and foodstuffs contaminated by the processing is likely lesser, but these are still significant exposure pathways. Although young children suffered the most immediate and severe consequences, results indicate that older children, adult workers, pregnant women, and breastfed infants are also at risk for lead poisoning. Mercury, arsenic, manganese, antimony, and crystalline silica exposures pose additional health threats. Conclusions: Results inform ongoing efforts in Nigeria to assess lead contamination and poisoning, treat victims, mitigate exposures, and remediate contamination. Ore deposit geology, pre-mining weathering, and burgeoning artisanal mining may combine to cause similar lead poisoning disasters elsewhere globally.

Environmental Health Perspectives↗
USGS2015

In-place oil shale resources of the Mahogany zone sorted by grade, overburden thickness and stripping ratio, Green River Formation, Piceance Basin, Colorado and Uinta Basin, Utah

A range of geological parameters relevant to mining oil shale have been examined for the Mahogany zone of the Green River Formation in the Piceance Basin, Colorado, and Uinta Basin, Utah, using information available in the U.S. Geological Survey Oil Shale Assessment database. Basinwide discrete and cumulative distributions of resource in-place as a function of (1) oil shale grade, (2) Mahogany zone thickness, (3) overburden thickness, and (4) stripping ratio (overburden divided by zone thickness) were determined for both basins on a per-acre basis, and a resource map showing the areal distribution of these properties was generated. Estimates of how much of the Mahogany zone resource meets various combinations of these parameters were also determined. Of the 191.7 billion barrels of Mahogany zone oil in-place in the Piceance Basin, 32.3 percent (61.8 billion barrels) is associated with oil shale yielding at least 25 gallons of oil per ton (GPT) of rock processed, is covered by overburden 1,000 feet thick or less, and has a stripping ratio of less than 10. In the Uinta Basin, 14.0 percent (29.9 billion barrels) of the 214.5 billion barrels of Mahogany zone oil in-place meets the same overburden and stripping ratio criteria but only for the lower grade cutoff of 15 GPT.

Colorado, Utah↗
USGS1990

Metallic-mineral assessment of the Aban Al Ahmar quadrangle, sheet 25F, Kingdom of Saudi Arabia

Comprehensive detailed interdisciplinary study assesses the metallic-mineral-resource potential in the Aban Al Ahmar Quadrangle of the Kingdom of Saudi Arabia, located in the eastern margin of the northeastern Arabian Shield, utilizing techniques of geophysics, geologic mapping, remote sensing and geochemistry. The landscape of the study area is characterized by isolated mountain groups, inselbergs, and local tracts of dissected hills separated by broad, low-relief peneplain. Topics covered include mining and exploration history; geological setting; interpretation of geophysical anomalies; limonitic hydrothermally altered and mineralized rocks; geochemical interpretation; mineral resource potential; skarn deposiits associated with intermediate igneous rocks; gold deposits; tin/tungsten skarn deposits; etc.

Aban Al Ahmar quadrangle↗
USGS1951

Geology of the Humboldt region and the Iron King mine, Bigbug mining district, Yavapai County, Arizona

The Humboldt region is in central Yavapai County, Arizona. The intersection of the 112? 15' meridian and the 34? 30' N parallel is in the approximate geographical center of the region, and the Iron King mine is about 2000 feet west-northwest of the intersection. Pre-Cambrian rocks form the bedrock in the Humboldt region. Late Cenozoic unconsolidated river wash and valley fill, including some interbedded basalt, locally mantle the pre-Cambrian rocks, especially in the north-central part of the region (Lonesome Valley). The pre-Cambrian rocks consist of five newly defined metavolcanic formations derived from flows and tuff s, and of six intrusive units ranging in composition from granite to gabbro or perhaps more mafic types. Relic bedding-and pillow structures are locally prominent in the metavolcanics; geopetal structures are uncommon, but where present, generally indicate that the top is toward the west, though the evidence is too meager to be conclusive. Low-grade dynamothermal metamorphism altered the metavolcanics and to a lesser extent the intrusive rocks, forming textures, structures, and mineral assemblages characteristic of low temperature and moderate stress. The Texas Gulch formation, which is the easternmost metavolcanic formation, consists of five lithologic units. Arranged in the general order of their appearance from east to west they are meta-andesite breccia, purple slate, metarhyolite tuff, meta-andesite, and green slate. The boundary between the Texas Gulch formation and the Iron King meta-andesite is apparently gradational. The Iron King meta-andesite consists of three meta-andesite tuff units, two meta-andesite flow units and one metarhyolite tuff and conglomerate unit. The assemblage chlorite-albite-epitode with or without quartz is dominant in the meta-andesites. Mafic intrusive rocks, which may be approximately contemporaneous with metamorphism, may explain the presence of actinolitic hornblende in the central part of the formation. Toward the west the Iron King meta-andesite appears to grade into the Spud Mountain metabreccia through a zone containing beds characteristic of either one formation or the other. The Spud Mountain metabreccia consists of interbedded metabreccia and metatuff beds. The metatuffs are largely andesitic in composition, but a few thin beds of metarhyolite tuff occur. The fragments in the metabreccia beds consist chiefly or porphyritic meta-andesites and the matrix is meta-andesite tuff. Pre-Cambrian faults now marked by dikes separate the Chaparral Gulch metavolcanics, which lie west of the Spud Mountain metabreccia, from underlying and overlying formations. The Chaparral Gulch metavolcanics contain metarhyolite tuff, metarhyolite flow, and meta-andesite tuff that locally was contaminated by rhyolitic detritus. The Indian Hills metavolcanics, which are northeast of the Chaparral Gulch metavolcanics, consist of two broad units, one composed of metarhyolites and the other of meta-andesites. Metamorphosed tuffs and flows are believed to be represented in both units and flow breccia in the meta-andesites. Granite and alaskite; granodiorite and quartz diorite; diorite, mafic quartz diorite, gabbro and diabase; metarhyolite (?); and quartz porphyry comprise the pre-Cambrian intrusive units mapped. They include both deep-seated and hypabyssal types. Dynamothermal metamorphism has foliated the smaller bodies and the margins of the larger masses and partly converted them into mineral assemblages stable under low-grade metamorphic conditions. Planar structures (chiefly foliation) are omnipresent and linear structures are common in the pre-Cambrian meta-volcanic rocks. North-trending planar structures dominate in the Indian Hills metavolcanics, and in the Spud Mountain metabreccia, whereas northeast-trending planar structures are dominant in the Texas Gulch formation, Iron King meta-andesite, and Chaparral Gulch metavolcanics. To a lesser extent northeast-trending st

Open-File Report↗
USGS1985

Geology and regional setting of the Al Masane ancient mine area, southeastern Arabian Shield, Kingdom of Saudi Arabia

Stratiform zinc-copper massive-sulfide deposits at Al Masane occur in thin dolomitic interbeds within Proterozoic felsic crystal tuff and mafic flows and volcaniclastics. These strata dip steeply westward and are underlain by shale and shaly graywacke to the east and overlain by lapilli crystal tuff to the west. This section is part of the Habawnah fold or mineral belt that extends from the Wadi Wassat area southward into Yemen. Western parts of the Habawnah fold belt, including the Al Masane area, are characterized by a bimodal assemblage of of phenocryst-poor basalts and sodic rhyolite crystal tuff, and by zinc-copper mineral deposits. Strata in the eastern part of the belt, mostly east of the Ashara fault zone, contain abundant phenocryst-rich mafic volcanic rocks, little felsic crystal tuff, and barren or locally nickeliferous massive pyrite deposits. Stratified rocks and gabbro sills of the Al Masane area were isoclinally folded and metamorphosed to the greenschist facies. Structural analysis indicates that foliation, lineation, joints, major and minor folds, and one of three sets of faults formed during a single east-west compressional deformational episode. Axial-plane foliation dips steeply westward and is usually coincident with bedding. Lineation plunges steeply to the northwest throughout the map area and is parallel to the intersection of joints of two major sets and to the intersection of these joints with foliation. Major folds have north-trending, gently plunging axes to which the axis of a minor fold set is essentially parallel. A second minor fold-set has a steeply plunging axis parallel to lineation. The Saadah massive-sulfide body is elongated by a fold of this system. Unmetamorphosed Proterozoic felsic sills, quartz monzonite and gabbro plutons, porphyritic diorite dikes, mafic dikes, and basalt dikes, in that apparent order, have intruded the stratified section. Basalt dikes are offset by southwestward-dipping reverse faults and by faults parallel to bedding. Malachite and metal-oxide-bearing gossans in the Al Masane area were mined in ancient times. Radiocarbon dating of charcoal in slag indicates that the ores were smelted about 1,200 years ago. Gossans are depleted in copper, silver, and zinc, relative to underlying sulfide, by factors of about 0.33, 0.2, and 0.08, respectively. Evaluation of numerous analyses of gossans, carbonates, and silicate rocks indicates that exploration for zinc-copper massive-sulfide deposits in the region should center on detailed geochemical studies of dolomitic beds. Dolomitization of host siliceous shales and tuffs and the formation of the massive-sulfide bodies at Al Masane probably caused by submarine fumarolic hydrothermal activity during periods of relative volcanic quiescence. Further work in the Al Masane region should include a study of the dolomitized areas and a search for other potential alteration "pipe" products (e.g. chlorite) as a guide to location of proximal deposits. Zinc-copper deposits at Al Masane and in the Dhahar-Al Hajrah and Kutam-Farah Garan areas have characteristics in common and are associated with felsic volcanic centers in the western bimodal part of the Habawnah mineral belt. They probably have parallel origins related to sea-floor volcanism. Deposits at Al Masane and Dhahar-Al Hajrah are possibly in the same general stratigraphic interval. Characteristics and distribution of altered rocks at Kutam suggest that the observed structural control of mineralization may represent remobilization. Chemical characteristics of volcanic rocks at Al Masane and elsewhere, along with features such as zinc-copper-iron sulfide mineralization, rhyolite-basalt bimodality, and the quartz phenocryst-rich nature of the felsic rocks, are compatible with an unusually primitive tholeiitic island-arc origin for the strata and mineral deposits of the Habawnah mineral belt.

Open-File Report↗