TY - Generic T1 - Age-constraints on fabric reactivation in the Tusas Range, northern New Mexico, using electron-microprobe monazite geochronology; implications for the nature of regional approximately 1400 Ga deformation T2 - Abstracts with Programs - Geological Society of America Y1 - 2002 A1 - Joseph P Kopera A1 - Williams, Michael L. A1 - Jercinovic, Michael J. KW - #StaffPubs KW - dates KW - deformation KW - electron probe data KW - fabric KW - folds KW - geochronology KW - Geochronology 03 KW - geometry KW - in situ KW - Laurentia KW - Mesoproterozoic KW - metamorphism KW - monazite KW - New Mexico KW - northern New Mexico KW - orogeny KW - Ortega Group KW - overgrowths KW - phosphates KW - Precambrian KW - preferred orientation KW - proterozoic KW - reactivation KW - Southwestern U.S. KW - strain KW - structural analysis KW - Structural geology 16 KW - synclines KW - tectonics KW - Tusas Mountains KW - United States KW - upper Precambrian KW - zoning AB - A key issue in constructing models for the southward growth of Laurentia during the Proterozoic is distinguishing the effects of approximately 1650 Ma and approximately 1400 Ma tectonism. These events share similar styles of deformation and metamorphism, making it difficult to assign structures, fabrics, and metamorphic phases to a particular event. The fundamental geometry of this orogen in the southwestern United States is defined in many areas by fold-fault pairs and isolated synclines of thick approximately 1700 Ma quartzite. In-situ EMP chemical dating of monazite, combined with detailed structural analysis, indicates that such synclines within the Tusas Range of northern New Mexico (locally F (sub 3) ) were substantially modified, if not developed, during approximately 1400 Ma tectonism. Monazite grains from the Ortega quartzite in the central Tusas Range display a shape preferred orientation parallel to the axial-planar fabric of these folds (S (sub 3) ), with overgrowth rims preferentially developed in the X direction of strain. These monazite grains have either >1700 Ma cores or approximately 1650 Ma cores with approximately 1400 Ma overgrowth rims, or are entirely approximately 1400 Ma in age. Field and microstructural observations show that the upright, east-west trending F (sub 3) and S (sub 3) are reactivations of older, northwest-trending fabrics and structures. The presence of approximately 1650 Ma overgrowth rims on monazite grains from the central and northern Tusas Range implies that these folds and fabrics may have nucleated prior to approximately 1400 Ma tectonism. Previous studies have shown an increase in approximately 1400 Ma monazite ages from north to south within the range, consistent with a similar increase in metamorphic grade. This gradient suggests that the central and northern Tusas may have been at progressively shallower crustal levels during approximately 1400 Ma tectonism, thus increasing the preservation of older fabrics, structures, and metamorphic monazite from south to north within the range. These observations support the hypothesis that approximately 1400 Ma tectonism locally reactivated and utilized pre-existing structures and fabrics, but had also profoundly shaped the geometry and metamorphic character of the orogen. JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 34 SN - 00167592 UR - http://silk.library.umass.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true&db=geh&AN=2004-044516&site=ehost-live&scope=site IS - 66 N1 - Accession Number: 2004-044516; Conference Name: Geological Society of America, 2002 annual meeting; Denver, CO, United States; Conference Date: 20021027; Language: English; Coden: GAAPBC; Collation: 1; Collation: 180; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200413; Monograph Title: Geological Society of America, 2002 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - Generic T1 - Arsenic in central Massachusetts bedrock and groundwater T2 - Abstracts with Programs - Geological Society of America Y1 - 2010 A1 - McTigue, David F. A1 - Stein, Carol L. A1 - Brandon, William C. A1 - Joseph P Kopera A1 - Keskula, Anna J. A1 - Koteas, G. Christopher KW - #StaffPubs KW - alteration KW - arsenic KW - arsenides KW - arsenopyrite KW - Ayer Granodiorite KW - BEDROCK KW - central Massachusetts KW - chelmsford granite KW - Devonian KW - dilation KW - discharge KW - dissolved materials KW - drinking water KW - Eh KW - fractures KW - General geochemistry 02A KW - geochemistry KW - granites KW - ground water KW - igneous rocks KW - joints KW - massachusetts KW - metals KW - metamorphism KW - meteoric water KW - overburden KW - Paleozoic KW - petrography KW - plutonic rocks KW - pollutants KW - reduction KW - solubility KW - solution KW - sulfides KW - theoretical models KW - United States AB - Across the New England "arsenic belt," groundwater arsenic (As) concentrations often exceed the EPA's 0.01-mg/L drinking water standard. In overburden groundwater at a site within this belt in north-central Massachusetts, As has been reported at levels up to 7.6 mg/L. Bedrock at the site consists of Silurian Central Maine Terrane metasediments intruded by the Devonian Ayer granodiorite and Chelmsford granite. Exchange of hydrothermal fluids between these lithologies during intrusion and later deformation, faulting, and metamorphism resulted in crystallization of arsenic-bearing minerals, including arsenopyrite. Quaternary deglaciation and unloading dilated joint systems in the bedrock, allowing increased exposure of the mineralogy to meteoric water. Several arsenopyrite alteration products (e.g., scorodite), of varying solubilities, precipitated on fracture surfaces and along grain boundaries between major phases. In the emerging conceptual model for this site, groundwater is recharged in bedrock uplands and moves downgradient through the fracture network, becoming increasingly reducing as it moves along a flow path. Arsenic dissolved from arsenopyrite and arsenic-bearing alteration phases in bedrock remains in solution until the groundwater discharges to lowland areas hydraulically downgradient. In these adjacent lowlands, glacial sand and gravel overburden lies above the bedrock. When the reducing water reaches more oxidizing conditions, As-sorbing hydrous ferric oxides (HFO) precipitate out on the aquifer solids, resulting in accumulation of As in the deep overburden aquifer. A large landfill at this site, now closed and capped, imposed reducing conditions, and As is mobilized into groundwater by reductive dissolution of the HFO. The presence of elevated As in groundwater is consistent with arsenic-bearing phases generated in granitoids at depth during regional metamorphism, which were subsequently altered, and are being solubilized at present by the circulation of shallow groundwater through varying redox environments. This scenario is supported by geochemical and petrographic studies of the granitoids and the occurrence of the highest groundwater and soil arsenic concentrations in the adjacent deep overburden. JF - Abstracts with Programs - Geological Society of America PB - Geological Society of America (GSA) : Boulder, CO, United States CY - United States VL - 42 SN - 00167592 UR - https://gsa.confex.com/gsa/2010AM/finalprogram/abstract_182430.htm IS - 55 N1 - Accession Number: 2011-044094; Conference Name: Geological Society of America, 2010 annual meeting; Denver, CO, United States; Conference Date: 20101031; Language: English; Coden: GAAPBC; Collation: 2; Collation: 216-217; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 201125; Monograph Title: Geological Society of America, 2010 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - JOUR T1 - Analyzing outcrop-scale fracture features to supplement investigations of bedrock aquifers JF - Hydrogeology Journal Y1 - 1997 A1 - Stephen B Mabee A1 - Hardcastle, Kenneth C. KW - #StaffPubs KW - aquifers KW - BEDROCK KW - boreholes KW - California KW - dip fractures KW - field studies KW - fractures KW - framework silicates KW - ground water KW - hydrodynamics KW - Hydrogeology 21 KW - laumontite KW - Madera County California KW - mapping KW - mineralization KW - movement KW - Raymond California KW - roughness KW - silicates KW - United States KW - zeolite group AB - A case study was conducted of 79 outcrops within 150 meters of the nine, 7590 m deep boreholes at the Lawrence Berkeley Laboratory (LBL) Fracture Hydrology Field Site in Raymond, California, USA, in order to make preliminary comparisons between surface fracture data and geophysical and hydrologic testing conducted in the boreholes. The orientation, trace length, spacing, roughness, planarity, associated mineralization, and domains (the geographic distribution of specific fracture sets) of 471 fractures were measured. Five families of steeply-dipping fractures and one family of shallow dipping fractures comprise 75 percent of the data and trend 52, 62, 130, 147, 173, and 35, respectively. The geographic distributions (domains) of the families, however, show the well field to be within the domains of the 62-, 173- and 35-trending families. The steeply-dipping fractures detected in the boreholes by LBL via acoustic televiewer logging trend about 65, 173, and 30 corroborating the findings of the fracture-domain analysis. Results indicate that the boreholes are located within a laumontite-mineralized area, including a steeply-dipping, 160-trending zone, 520 cm wide, of laumontite-rich pods that transects the boreholes. Independent hydrologic tests by LBL revealed a 160-trending barrier to groundwater flow between some of the boreholes, precisely where the 160-trending zone of laumontite-mineralized pods was mapped. PB - Verlag Heinz Heise : Hanover, Federal Republic of Germany CY - Federal Republic of Germany VL - 5 SN - 1431217414350157 UR - http://link.springer.com/article/10.1007/s100400050106 IS - 4 N1 - Accession Number: 1998-019185; Language: English; Language of Summary: French; Spanish; Coordinates: N364500N374500W1190100W1203800; Collation: 16; Publication Types: Serial; Updated Code: 199808; Illustration(s): illus. incl. 3 tables, sketch maps; Number of References: 28; Reviewed Item: Analytic JO - Hydrogeology Journal ER - TY - Generic T1 - Active mines and mineral plants in the US Y1 - KW - #MapsDataPublications KW - #MineralResources KW - active KW - collecting KW - dimension stone KW - economic geology KW - gold KW - lead KW - minerals KW - mines KW - quarries KW - sand and gravel KW - sand pits KW - silver AB - Mine plants and operations for commodities monitored by the National Minerals Information Center of the USGS. Operations included are those considered active in 2003 and surveyed by the USGS. PB - USGS UR - http://tin.er.usgs.gov/mineplant/ ER - TY - Generic T1 - The American Geological Institute - News and Resources for geoscientists and teachers Y1 - KW - #EducationalResources KW - #ProfessionalDevelopment KW - activities KW - classroom KW - curricula KW - earth science KW - education KW - GEOLOGY KW - K-12 KW - lesson plans KW - news KW - schools KW - standards KW - teacher resources KW - teaching PB - AGI UR - http://www.agiweb.org/index.html ER -