@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 {294,
	title = {Fracture characterization of crystalline bedrock for groundwater investigations; an example from the Marlborough Quadrangle, Massachusetts},
	volume = {36},
	year = {2004},
	note = {Accession Number: 2005-077195; Conference Name: Geological Society of America, Northeastern Section, 38th annual meeting; Geological Society of America, Southeastern Section, 53rd annual meeting; Washington, DC, United States; Conference Date: 20040325; Language: English; Coordinates: N421800N421800W0713000W0713000; Coden: GAAPBC; Collation: 1; Collation: 113; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200524; Monograph Title: Geological Society of America, Northeastern Section, 38th annual meeting; Geological Society of America, Southeastern Section, 53rd annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {2004/03/01/},
	pages = {113 - 113},
	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). The Marlborough Quadrangle, about 40 km west of Boston, was selected as a test case of how a state geological survey can most effectively and efficiently collect and present such data in order to better constrain conceptual models of groundwater flow in general and to be of maximum use for hydrologists and consultants working on specific local problems. In this study, 3200 structural measurements were taken by a two-person team over a nine-week period at 68 stations distributed throughout the quadrangle and keyed into a GIS database. Specialized data sheets allowed efficient recording and digitization of orientations, lengths, spacing and mineralization, and separation of various classes of joints and veins. Fault data also included motion direction and sense. Summary maps in GIS format include standard geologic map bases overlain by typical rose diagrams and stereograms and maps such as fracture domains and trajectories, sheeting distribution, foliation trajectories, bedrock elevations, generalized piezometric surface configuration, and overburden type and thickness with separations into permeability class. Geology of the quadrangle can be separated into three zones: (a) north of the Assabet River Fault (ARF), (b) the area between the ARF and 1.5 km-wide Bloody Bluff Fault Zone (BBFZ), and (c) south of the BBFZ. Generalized foliations in the zones are: (a) 215, 50N, (b) 240, 65N, and (c) 270, 45N. Two pervasive, steeply-dipping (>60 degrees ) fracture sets occur throughout the quadrangle: an older 150 degrees set that includes sulfide-bearing veins and fracture surfaces along the ARF and a 015 degrees set of largely unmineralized common joints, macrojoints (>3 m length) and joint zones (av. 1.2 m width). Sheeting and unloading joints are generally coincident with shallow dipping foliation in (c) but cross-cut foliation in (a) and (b). 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, aquifers, Assabet River Fault, BEDROCK, characterization, controls, crystalline rocks, fractured materials, fractures, geographic information systems, ground water, Hydrogeology 21, hydrology, information systems, joints, Marlborough Quadrangle, massachusetts, Middlesex County Massachusetts, permeability, preferential flow, recharge, style, testing, theoretical models, United States},
	isbn = {00167592},
	url = {https://gsa.confex.com/gsa/2004NE/finalprogram/abstract_70321.htm},
	author = {Scott A Salamoff and Stephen B Mabee and Joseph P Kopera and Donald U Wise}
}
