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 - Generic T1 - The influence of ductile structure and rheological heterogeneity on brittle structures as exhibited by Avalonian granites in southeastern Massachusetts T2 - Geological Society of America Abstracts with Programs Y1 - 2008 A1 - Joseph P Kopera KW - #StaffPubs KW - acadian KW - alleghenian KW - avalon KW - BEDROCK KW - dikes KW - foliation KW - fracture KW - fracture system KW - fracture trace KW - fractures KW - granite KW - granites KW - Hopkinton KW - joints KW - l-tectonites KW - lineaments KW - lineation KW - Milford KW - Upton AB - The orientation and geographic distribution of joints, veins, and brittle faults show a conspicuous correlation with the heterogeneous distribution of foliation and lineation intensity in Neo-Proterozoic granites and their deformed counterparts in southeastern Massachusetts. Field mapping and stereonet analysis of brittle and ductile structural data collected during 1:24,000-scale geologic mapping of the Milford quadrangle yielded the following general observations, which suggest that the ductile deformational history of this region appears to have strongly influenced the later development of brittle structures in the same rocks:
Fracture Characterization Map is included as sheets 2 and 3. Water Resources data included as sheet 4.
GIS and metadata forthcoming
JF - Open-File Report PB - Massachusetts Geological Survey U2 -1:24000
ER - TY - MAP T1 - Preliminary bedrock Geology of the Northern Portion of the Blackstone quadrangle, Massachusetts Y1 - 2008 A1 - Joseph P Kopera A1 - Shaw, C.J. KW - #BedrockMaps KW - #MGSPub KW - acadian KW - alleghenian KW - avalon KW - bedrock map KW - Bellingham KW - blackstone KW - GEOLOGIC MAP KW - gneiss KW - granite KW - hopedale quartzite KW - ironstone diorite KW - Mendon KW - MGS Publication KW - Milford KW - Millville KW - neoproterozoic KW - Northbridge KW - proterozoic KW - quarries KW - Upton KW - Uxbridge AB -This map is an interim progress report of mapping currently underway.
JF - Open-File Report PB - Massachusetts Geological Survey UR - http://www.geo.umass.edu/stategeologist/ U2 -1:24000
ER -