TY - Generic T1 - Evidence for arsenic-mineralization in granitic basement rocks, Ayer Granodiorite, northeastern Massachusetts T2 - Abstracts with Programs - Geological Society of America Y1 - 2010 A1 - Koteas, G. Christopher A1 - Keskula, Anna J. A1 - Stein, Carol L. A1 - McTigue, David F. A1 - Joseph P Kopera A1 - Brandon, William C. KW - #StaffPubs KW - acadian KW - arsenic KW - arsenides KW - arsenopyrite KW - Ayer Granodiorite KW - Berwick formation KW - fractured materials KW - geochemistry KW - granodiorites KW - Igneous and metamorphic petrology 05A KW - igneous rocks KW - lower Paleozoic KW - massachusetts KW - Merrimack Synclinorium KW - metals KW - metamorphic rocks KW - metamorphism KW - metasedimentary rocks KW - metasomatism KW - Middlesex County Massachusetts KW - migration of elements KW - mineralization KW - Mineralogy of non-silicates 01C KW - northeastern Massachusetts KW - orogeny KW - Paleozoic KW - plutonic rocks KW - pollutants KW - pollution KW - pyrite KW - sulfides KW - United States AB - Core samples of the Ayer Granodiorite along the eastern margin of the Merrimack Belt in northeastern Massachusetts host a series of sulfide and oxide phases that resulted from interaction with sulfide-bearing meta-sedimentary host rocks. Euhedral arsenopyrite grains are found with ilmenite, apatite, and REE phosphates in zones that generally mimic the intersection between a gneissic fabric and a relict magmatic foliation. Arsenopyrite crystals are typically elongate with this lineation. Euhedral to subhedral pyrite crystals have also been observed, but are localized to areas without As-bearing phases. Micro-fractures that parallel either a steep NW-striking joint set or gently-dipping sheeting joints are commonly filled with interwoven calcite cements and As-bearing Fe-oxides. Surface coatings of major fracture sets are also characterized by Fe-As-rich rinds that host micron-scale sub-angular particles of quartz, feldspars, and phyllosilicates. Where micro-fractures are most concentrated, sulfide-bearing minerals are less common; however, subhedral to anhedral arsenopyrite grains do occur along some open micro-fractures. These crystals preserve lobate grain boundaries and are associated with As-bearing Fe-oxide-rich coatings along adjacent fractures. The presence of 1) pyrite, 2) arsenopyrite associated with phosphates, and 3) As-bearing fracture coatings suggests multiple stages of mineralization. We propose that intrusion-related fluid-rock interaction associated with heating of nearby sulfide-bearing schists of the Berwick Formation during Acadian orogenesis may have provided the necessary constituents for growth of sulfide phases in the Ayer. It appears that Late Devonian greenschist facies metamorphism and metasomatism led to mineralization that generated arsenopyrite and accompanying phosphates; however, the role of the cross-cutting Clinton Newbury Fault Zone as a conduit for hydrothermal fluids may also be important. Lower temperature As-bearing Fe-oxide and calcite coatings on open fractures surfaces may be associated with a change from lithostatic- to hydrostatic-pressures during post-glacial regional uplift. This mineralization appears to be synchronous with intense microfracturing that post-dates all other mineralization. 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/2010NE/finalprogram/abstract_169998.htm IS - 11 N1 - Accession Number: 2010-100047; Conference Name: Geological Society of America, Northeastern Section, 45th annual meeting; Geological Society of America, Southeastern Section, 59th annual meeting; Baltimore, MD, United States; Conference Date: 20100314; Language: English; Coordinates: N420800N424400W0710200W0715300; Coden: GAAPBC; Collation: 1; Collation: 160; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 201052; Monograph Title: Geological Society of America, Northeastern Section, 45th annual meeting; Geological Society of America, Southeastern Section, 59th annual meeting; joint meeting, abstracts volume; Monograph Author(s): Anonymous; Reviewed Item: Analytic JO - Abstracts with Programs - Geological Society of America ER - TY - MAP T1 - [Draft] Preliminary bedrock geologic map of the Lawrence quadrangle, Massachusetts Y1 - 2005 A1 - Castle, R.O. A1 - Hepburn, J.C. A1 - Joseph P Kopera KW - #BedrockMaps KW - #MGSPub KW - Andover KW - Andover Granite KW - Bedford KW - Berwick formation KW - Clinton-Newbury Fault KW - Dracut KW - Elliot formation KW - Lawrence KW - Methuen KW - nashoba KW - North Andover KW - tadmuck brook schist KW - Tewksbury JF - Open-File Report PB - Massachusetts Geological Survey U2 -

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ER - TY - MAP T1 - Preliminary bedrock geologic map of the Ayer quadrangle, Massachusetts Y1 - 2006 A1 - Joseph P Kopera KW - #BedrockMaps KW - #MGSPub KW - arsenic KW - Ayer KW - ayer granite KW - Berwick formation KW - Boxborough KW - chelmsford granite KW - Clinton-Newbury Fault KW - Devens KW - Fort Devens KW - Groton KW - Harvard KW - Jahns KW - LITTLETON KW - Merrimack Terrane KW - mylonite KW - nashoba KW - Nashua Trough KW - Oakdale formation KW - Shepley's Hill Landfill KW - Shirley KW - tadmuck brook schist KW - Worcester Formation AB -

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

JF - Open-File Report PB - Massachusetts Geological Survey UR - http://www.geo.umass.edu/stategeologist/ U2 -

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ER - TY - MAP T1 - Preliminary bedrock geologic map of the Westford quadrangle, Massachusetts Y1 - 2009 A1 - Joseph P Kopera A1 - D.C. Alvord A1 - Richard H Jahns A1 - M.E. Willard A1 - W.S. White KW - #BedrockMaps KW - #MGSPub KW - Acton KW - amphibolite KW - ayer granite KW - Berwick formation KW - Boxborough KW - calc-silicates KW - Carlisle KW - Chelmsford KW - chelmsford granite KW - Clinton-Newbury Fault KW - Concord KW - diorite KW - gneiss KW - Groton KW - LITTLETON KW - magnetite KW - marble KW - migmatite KW - Nashoba Formation KW - phyllonite KW - tadmuck brook schist KW - Tyngsborough KW - Westford AB - Bedrock Geologic Map contains brittle fracture data Mapping still in progress. For interim fracture database, please contact Joe Kopera JF - Open-File Report PB - Massachusetts Geological Survey U2 -

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ER - TY - MAP T1 - Progress map of the preliminary bedrock geologic map of the Billerica quadrangle, Massachusetts Y1 - 2011 A1 - Matthew A Massey KW - #BedrockMaps KW - #FractureMaps KW - #MGSPub KW - Bedford KW - Berwick formation KW - Billerica KW - Billerica Schist KW - Boxford formation KW - Carlisle KW - Chelmsford KW - Clinton-Newbury Fault Zone KW - Concord KW - fracture KW - gneiss KW - joints KW - Lowell KW - magnetite KW - migmatite KW - nashoba KW - schist KW - Spencer Brook Fault KW - tadmuck brook schist KW - Tewksbury AB - This map also contains brittle fracture data as part of the GIS files. This map is a progress report of bedrock geologic mapping currently underway in the Billerica quadrangle. It is a compilation of ongoing field mapping (Massey, this study) and previously published work in the area (Alvord, 1973, 1975; Jahns et al.1959). The Billerica quadrangle is located approximately 20 miles northwest of Boston along Route 3, just south of Lowell, in northeastern Massachusetts, encompassing the northwestern most Nashoba terrane and it’s boundary with the Merrimack belt (Figure 1). In the Billerica quadrangle, the Merrimack Belt consists of limited exposures of highly strained metasediments, or possibly orthoschist derived from reconstituted igne- ous protolith. The Clinton-Newbury fault zone separates the Merrimack Belt from multiply deformed, polymetamorphic biotite gneisses, migmatites, and amphibolites of the Nashoba terrane. PB - Massachusetts Geological Survey U2 - 1:24000 ER - TY - MAP T1 - Progress report of bedrock geologic mapping of the Lowell quadrangle, Massachusetts Y1 - 2010 A1 - Richard H Jahns A1 - Joseph P Kopera KW - #BedrockMaps KW - #MGSPub KW - Berwick formation KW - Chelmsford KW - Clinton-Newbury Fault KW - Dracut KW - Dracut diorite KW - Dracut gabbro KW - Dracut pluton KW - gabbro KW - Jahns KW - Lowell KW - Methuen KW - nashoba KW - Nashoba Formation KW - Tewksbury KW - Tyngsborough AB -

Maps in Progress are not distributed to the public. If you would like to see a copy of this map, please contact Joseph Kopera at jkopera[at]geo[dot]geo[dot]umass[dot]edu

JF - Progress Map PB - Massachusetts Geological Survey U2 -

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