@proceedings {268,
	title = {Age-constraints on fabric reactivation in the Tusas Range, northern New Mexico, using electron-microprobe monazite geochronology; implications for the nature of regional approximately 1400 Ga deformation},
	volume = {34},
	year = {2002},
	note = {Accession Number: 2004-044516; Conference Name: Geological Society of America, 2002 annual meeting; Denver, CO, United States; Conference Date: 20021027; Language: English; Coden: GAAPBC; Collation: 1; Collation: 180; Publication Types: Abstract Only; Serial; Conference document; Updated Code: 200413; Monograph Title: Geological Society of America, 2002 annual meeting; Monograph Author(s): Anonymous; Reviewed Item: Analytic},
	month = {2002/10/01/},
	pages = {180 - 180},
	publisher = {Geological Society of America (GSA) : Boulder, CO, United States},
	address = {United States},
	abstract = {A key issue in constructing models for the southward growth of Laurentia during the Proterozoic is distinguishing the effects of approximately 1650 Ma and approximately 1400 Ma tectonism. These events share similar styles of deformation and metamorphism, making it difficult to assign structures, fabrics, and metamorphic phases to a particular event. The fundamental geometry of this orogen in the southwestern United States is defined in many areas by fold-fault pairs and isolated synclines of thick approximately 1700 Ma quartzite. In-situ EMP chemical dating of monazite, combined with detailed structural analysis, indicates that such synclines within the Tusas Range of northern New Mexico (locally F (sub 3) ) were substantially modified, if not developed, during approximately 1400 Ma tectonism. Monazite grains from the Ortega quartzite in the central Tusas Range display a shape preferred orientation parallel to the axial-planar fabric of these folds (S (sub 3) ), with overgrowth rims preferentially developed in the X direction of strain. These monazite grains have either >1700 Ma cores or approximately 1650 Ma cores with approximately 1400 Ma overgrowth rims, or are entirely approximately 1400 Ma in age. Field and microstructural observations show that the upright, east-west trending F (sub 3) and S (sub 3) are reactivations of older, northwest-trending fabrics and structures. The presence of approximately 1650 Ma overgrowth rims on monazite grains from the central and northern Tusas Range implies that these folds and fabrics may have nucleated prior to approximately 1400 Ma tectonism. Previous studies have shown an increase in approximately 1400 Ma monazite ages from north to south within the range, consistent with a similar increase in metamorphic grade. This gradient suggests that the central and northern Tusas may have been at progressively shallower crustal levels during approximately 1400 Ma tectonism, thus increasing the preservation of older fabrics, structures, and metamorphic monazite from south to north within the range. These observations support the hypothesis that approximately 1400 Ma tectonism locally reactivated and utilized pre-existing structures and fabrics, but had also profoundly shaped the geometry and metamorphic character of the orogen.},
	keywords = {$\#$StaffPubs, dates, deformation, electron probe data, fabric, folds, geochronology, Geochronology 03, geometry, in situ, Laurentia, Mesoproterozoic, metamorphism, monazite, New Mexico, northern New Mexico, orogeny, Ortega Group, overgrowths, phosphates, Precambrian, preferred orientation, proterozoic, reactivation, Southwestern U.S., strain, structural analysis, Structural geology 16, synclines, tectonics, Tusas Mountains, United States, upper Precambrian, zoning},
	isbn = {00167592},
	url = {http://silk.library.umass.edu/login?url=http://search.ebscohost.com/login.aspx?direct=true\&db=geh\&AN=2004-044516\&site=ehost-live\&scope=site},
	author = {Joseph P Kopera and Williams, Michael L. and Jercinovic, Michael J.}
}
@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.}
}
