%0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2010 %T Evidence for arsenic-mineralization in granitic basement rocks, Ayer Granodiorite, northeastern Massachusetts %A Koteas, G. Christopher %A Keskula, Anna J. %A Stein, Carol L. %A McTigue, David F. %A Joseph P Kopera %A Brandon, William C. %K #StaffPubs %K acadian %K arsenic %K arsenides %K arsenopyrite %K Ayer Granodiorite %K Berwick formation %K fractured materials %K geochemistry %K granodiorites %K Igneous and metamorphic petrology 05A %K igneous rocks %K lower Paleozoic %K massachusetts %K Merrimack Synclinorium %K metals %K metamorphic rocks %K metamorphism %K metasedimentary rocks %K metasomatism %K Middlesex County Massachusetts %K migration of elements %K mineralization %K Mineralogy of non-silicates 01C %K northeastern Massachusetts %K orogeny %K Paleozoic %K plutonic rocks %K pollutants %K pollution %K pyrite %K sulfides %K United States %X 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. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 42 %P 160 - 160 %8 2010/03/01/ %@ 00167592 %G eng %U https://gsa.confex.com/gsa/2010NE/finalprogram/abstract_169998.htm %N 11 %! Abstracts with Programs - Geological Society of America %0 Map %D 2005 %T [Draft] Preliminary bedrock geologic map of the Lawrence quadrangle, Massachusetts %A Castle, R.O. %A Hepburn, J.C. %A Joseph P Kopera %K #BedrockMaps %K #MGSPub %K Andover %K Andover Granite %K Bedford %K Berwick formation %K Clinton-Newbury Fault %K Dracut %K Elliot formation %K Lawrence %K Methuen %K nashoba %K North Andover %K tadmuck brook schist %K Tewksbury %B Open-File Report %I Massachusetts Geological Survey %G eng %2

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%0 Map %D 2006 %T Preliminary bedrock geologic map of the Ayer quadrangle, Massachusetts %A Joseph P Kopera %K #BedrockMaps %K #MGSPub %K arsenic %K Ayer %K ayer granite %K Berwick formation %K Boxborough %K chelmsford granite %K Clinton-Newbury Fault %K Devens %K Fort Devens %K Groton %K Harvard %K Jahns %K LITTLETON %K Merrimack Terrane %K mylonite %K nashoba %K Nashua Trough %K Oakdale formation %K Shepley's Hill Landfill %K Shirley %K tadmuck brook schist %K Worcester Formation %X

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

%B Open-File Report %7 OFR-06-02 %I Massachusetts Geological Survey %G eng %U http://www.geo.umass.edu/stategeologist/ %2

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%0 Map %D 2009 %T Preliminary bedrock geologic map of the Westford quadrangle, Massachusetts %A Joseph P Kopera %A D.C. Alvord %A Richard H Jahns %A M.E. Willard %A W.S. White %K #BedrockMaps %K #MGSPub %K Acton %K amphibolite %K ayer granite %K Berwick formation %K Boxborough %K calc-silicates %K Carlisle %K Chelmsford %K chelmsford granite %K Clinton-Newbury Fault %K Concord %K diorite %K gneiss %K Groton %K LITTLETON %K magnetite %K marble %K migmatite %K Nashoba Formation %K phyllonite %K tadmuck brook schist %K Tyngsborough %K Westford %X Bedrock Geologic Map contains brittle fracture data Mapping still in progress. For interim fracture database, please contact Joe Kopera %B Open-File Report %7 OFR-09-01 %I Massachusetts Geological Survey %G eng %2

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%0 Map %D 2011 %T Progress map of the preliminary bedrock geologic map of the Billerica quadrangle, Massachusetts %A Matthew A Massey %K #BedrockMaps %K #FractureMaps %K #MGSPub %K Bedford %K Berwick formation %K Billerica %K Billerica Schist %K Boxford formation %K Carlisle %K Chelmsford %K Clinton-Newbury Fault Zone %K Concord %K fracture %K gneiss %K joints %K Lowell %K magnetite %K migmatite %K nashoba %K schist %K Spencer Brook Fault %K tadmuck brook schist %K Tewksbury %X 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. %7 OFR11-03 %I Massachusetts Geological Survey %G eng %2 1:24000 %0 Map %D 2010 %T Progress report of bedrock geologic mapping of the Lowell quadrangle, Massachusetts %A Richard H Jahns %A Joseph P Kopera %K #BedrockMaps %K #MGSPub %K Berwick formation %K Chelmsford %K Clinton-Newbury Fault %K Dracut %K Dracut diorite %K Dracut gabbro %K Dracut pluton %K gabbro %K Jahns %K Lowell %K Methuen %K nashoba %K Nashoba Formation %K Tewksbury %K Tyngsborough %X

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

%B Progress Map %7 PM-09-01 %I Massachusetts Geological Survey %G eng %2

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