@proceedings {271,
	title = {Arsenic in central Massachusetts bedrock and groundwater},
	volume = {42},
	year = {2010},
	note = {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},
	month = {2010/11/01/},
	pages = {216 - 217},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {Across the New England "arsenic belt," groundwater arsenic (As) concentrations often exceed the EPA{\textquoteright}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.},
	keywords = {$\#$StaffPubs, alteration, arsenic, arsenides, arsenopyrite, Ayer Granodiorite, BEDROCK, central Massachusetts, chelmsford granite, Devonian, dilation, discharge, dissolved materials, drinking water, Eh, fractures, General geochemistry 02A, geochemistry, granites, ground water, igneous rocks, joints, massachusetts, metals, metamorphism, meteoric water, overburden, Paleozoic, petrography, plutonic rocks, pollutants, reduction, solubility, solution, sulfides, theoretical models, United States},
	isbn = {00167592},
	url = {https://gsa.confex.com/gsa/2010AM/finalprogram/abstract_182430.htm},
	author = {McTigue, David F. and Stein, Carol L. and Brandon, William C. and Joseph P Kopera and Keskula, Anna J. and Koteas, G. Christopher}
}
@proceedings {293,
	title = {Fracture characterization maps; a new type of geologic map for hydrogeologic applications},
	volume = {37},
	year = {2005},
	note = {Accession Number: 2006-039166; Conference Name: Geological Society of America, 2005 annual meeting; Salt Lake City, UT, United States; Conference Date: 20051016; Language: English; Coden: GAAPBC; Collation: 1; Collation: 145; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200612; Monograph Title: Geological Society of America, 2005 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {2005/10/01/},
	pages = {145 - 145},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {Integration of a wide array of structural data with well-field hydrologic testing is increasingly recognized as a critical step in understanding groundwater flow behavior and recharge in crystalline bedrock aquifers (Lyford et al., 2003, Walsh and Lyford, 2002). As part of its rejuvenated mapping program, The Massachusetts Office of the State Geologist has been producing fracture characterization maps as a value-added accompaniment to traditional 1:24:000-scale bedrock mapping. Fracture characterization maps reclassify bedrock into domains of varying hydrologic significance, by combining rock properties (foliation steepness and development, partings, sheeting development, etc...) and type of overburden (permeable vs. non-permeable). The goal of these maps is to better understand preferential flow directions in the bedrock and the potential hydraulic connections between surficial and bedrock aquifers. Each fracture characterization map contains several summary panels, including standard geologic map bases overlain by typical rose diagrams and stereonets displaying fracture domains and trajectories, sheeting distribution, foliation trajectories, bedrock elevations, generalized piezometric surface configuration, and overburden type and thickness with separations into permeability class. A GIS well database is also included, showing well distribution, yield, bedrock elevation, and "hot-linked" well log images. All maps and raw data are made available to the public in paper, digital (PDF) or GIS format. We believe this approach will provide hydrologists and consultants with basic framework data that will expedite and improve the planning of subsurface investigations, construction activities, and groundwater exploration.},
	keywords = {$\#$StaffPubs, applications, aquifers, BEDROCK, characterization, classification, crystalline rocks, exploration, fractures, ground water, hydrodynamics, Hydrogeology 21, mapping, movement, overburden, permeability, potentiometric surface, spatial distribution, surficial aquifers, thickness, water wells, water yield},
	isbn = {00167592},
	url = {https://gsa.confex.com/gsa/2005AM/finalprogram/abstract_94576.htm},
	author = {Stephen B Mabee and Joseph P Kopera}
}
