@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} } @Map {360, title = {Bedrock geologic map of the Ayer 7.5{\textquoteright} quadrangle, Worcester and Middlesex Counties, Massachusetts}, publisher = {Massachusetts Geological Survey}, edition = {15-01}, abstract = {

Editing and review are still underway. \ This map should be available in winter 2015/2016

}, keywords = {Ayer, ayer granite, Ayer Granodiorite, Ayer Quadrangle, Berwick, Campbell Hill Fault, chelmsford granite, Clinton Newbury Fault, Devens, Harvard Conglomerate, merrimack, Oakdale formation, pin hill, Shepley{\textquoteright}s Hill, Shirley Fault, tadmuck brook schist, Worcester Formation}, author = {Kopera J.P.} } @Map {359, title = {Bedrock geologic map of the Ayer 7.5{\textquoteright} quadrangle, Worcester and Middlesex Counties, Massachusetts (2015)}, publisher = {Massachusetts Geological Survey}, edition = {15-01}, abstract = {

Editing and review are still underway. \ This map should be available in winter 2015/2016

}, keywords = {Ayer, ayer granite, Ayer Granodiorite, Ayer Quadrangle, Berwick, Campbell Hill Fault, chelmsford granite, Clinton Newbury Fault, Devens, Harvard Conglomerate, merrimack, Oakdale formation, pin hill, Shepley{\textquoteright}s Hill, Shirley Fault, tadmuck brook schist, Worcester Formation}, author = {Joseph P Kopera} } @Map {221, title = {Preliminary Bedrock Geologic Map of the area surrounding Shepley{\textquoteright}s Hill, Towns of Ayer and Devens, Massachusetts}, year = {2008}, publisher = {Massachusetts Geological Survey}, edition = {OFR08-05}, keywords = {$\#$BedrockMaps, $\#$MGSPub, army, arsenic, Ayer, ayer granite, chelmsford granite, Clinton Newbury Fault Zone, Devens, landfill}, author = {Joseph P Kopera} } @Map {238, title = {Preliminary bedrock geologic map of the Ayer quadrangle, Massachusetts}, year = {2006}, publisher = {Massachusetts Geological Survey}, edition = {OFR-06-02}, abstract = {

This preliminary version of the Bedrock Map of the Ayer Quadrangle (Kopera, 2006) has been removed pending the release of an updated version in the near future. The above version should be considered outdated. If you would like a copy of this map, please contact Joseph Kopera at jkopera[at]geo[dot]geo[dot] umass[dot]edu

}, keywords = {$\#$BedrockMaps, $\#$MGSPub, arsenic, Ayer, ayer granite, Berwick formation, Boxborough, chelmsford granite, Clinton-Newbury Fault, Devens, Fort Devens, Groton, Harvard, Jahns, LITTLETON, Merrimack Terrane, mylonite, nashoba, Nashua Trough, Oakdale formation, Shepley{\textquoteright}s Hill Landfill, Shirley, tadmuck brook schist, Worcester Formation}, url = {http://www.geo.umass.edu/stategeologist/}, author = {Joseph P Kopera} } @Map {245, title = {Preliminary bedrock geologic map of the Westford quadrangle, Massachusetts}, year = {2009}, publisher = {Massachusetts Geological Survey}, edition = {OFR-09-01}, abstract = {Bedrock Geologic Map contains brittle fracture data Mapping still in progress. For interim fracture database, please contact Joe Kopera }, keywords = {$\#$BedrockMaps, $\#$MGSPub, Acton, amphibolite, ayer granite, Berwick formation, Boxborough, calc-silicates, Carlisle, Chelmsford, chelmsford granite, Clinton-Newbury Fault, Concord, diorite, gneiss, Groton, LITTLETON, magnetite, marble, migmatite, Nashoba Formation, phyllonite, tadmuck brook schist, Tyngsborough, Westford}, author = {Joseph P Kopera and D.C. Alvord and Richard H Jahns and M.E. Willard and W.S. White} } @Map {235, title = {Preliminary fracture characterization map of the Ayer quadrangle, Massachusetts}, year = {2006}, publisher = {Massachusetts Geological Survey}, edition = {OFR-06-03}, abstract = {This preliminary version of the Fracture Characterization Map of the Ayer Quadrangle (Kopera, 2006) has been removed pending the release of an updated version of the underlying bedrock geologic map in the near future. The above version should be considered outdated. If you would like a copy of the outdated map, please contact Joseph Kopera at jkopera[at]geo[dot]geo[dot]umass[dot]edu }, keywords = {$\#$FractureMaps, $\#$MGSPub, Ayer, ayer granite, Boxborough, chelmsford granite, Devens, fault, Fort Devens, fracture, fracture trace, Groton, Harvard, hydrostructural domain, joint, lineament, LITTLETON, Shirley, water resources}, author = {Joseph P Kopera and Stephen B Mabee and Powers, D.C.} }