@proceedings {284, title = {Evidence for arsenic-mineralization in granitic basement rocks, Ayer Granodiorite, northeastern Massachusetts}, volume = {42}, year = {2010}, note = {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}, month = {2010/03/01/}, pages = {160 - 160}, publisher = {Geological Society of America (GSA) : Boulder, CO, United States}, address = {United States}, abstract = {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.}, keywords = {$\#$StaffPubs, acadian, arsenic, arsenides, arsenopyrite, Ayer Granodiorite, Berwick formation, fractured materials, geochemistry, granodiorites, Igneous and metamorphic petrology 05A, igneous rocks, lower Paleozoic, massachusetts, Merrimack Synclinorium, metals, metamorphic rocks, metamorphism, metasedimentary rocks, metasomatism, Middlesex County Massachusetts, migration of elements, mineralization, Mineralogy of non-silicates 01C, northeastern Massachusetts, orogeny, Paleozoic, plutonic rocks, pollutants, pollution, pyrite, sulfides, United States}, isbn = {00167592}, url = {https://gsa.confex.com/gsa/2010NE/finalprogram/abstract_169998.htm}, author = {Koteas, G. Christopher and Keskula, Anna J. and Stein, Carol L. and McTigue, David F. and Joseph P Kopera and Brandon, William C.} } @proceedings {351, title = {The influence of ductile structure and rheological heterogeneity on brittle structures as exhibited by Avalonian granites in southeastern Massachusetts}, volume = {40}, year = {2008}, month = {03/2008}, pages = {3}, publisher = {Geological Society of America (GSA) : Boulder, CO, United States}, edition = {2}, address = {Buffalo, NY}, abstract = {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
}, keywords = {$\#$BedrockMaps, $\#$FractureMaps, $\#$MGSPub, acadian, alaskite, alleghenian, amphibolite, antiform, Ashland, avalon, bedrock map, blackstone, fracture, GEOLOGIC MAP, gneiss, granite, Holliston, hopedale quartzite, Hopkinton, ironstone diorite, joints, l-tectonite, Mendon, MGS Publication, Milford, neoproterozoic, Northbridge, proterozoic, quarries, quartzite, Upton, Westborough}, author = {Joseph P Kopera and Shaw, C.E. and Fernandez, M.} } @Map {217, title = {Preliminary bedrock Geology of the Northern Portion of the Blackstone quadrangle, Massachusetts}, year = {2008}, publisher = {Massachusetts Geological Survey}, edition = {OFR-08-03}, abstract = {This map is an interim progress report of mapping currently underway.
}, keywords = {$\#$BedrockMaps, $\#$MGSPub, acadian, alleghenian, avalon, bedrock map, Bellingham, blackstone, GEOLOGIC MAP, gneiss, granite, hopedale quartzite, ironstone diorite, Mendon, MGS Publication, Milford, Millville, neoproterozoic, Northbridge, proterozoic, quarries, Upton, Uxbridge}, url = {http://www.geo.umass.edu/stategeologist/}, author = {Joseph P Kopera and Shaw, C.J.} }