%0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2002 %T 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 %A Joseph P Kopera %A Williams, Michael L. %A Jercinovic, Michael J. %K #StaffPubs %K dates %K deformation %K electron probe data %K fabric %K folds %K geochronology %K Geochronology 03 %K geometry %K in situ %K Laurentia %K Mesoproterozoic %K metamorphism %K monazite %K New Mexico %K northern New Mexico %K orogeny %K Ortega Group %K overgrowths %K phosphates %K Precambrian %K preferred orientation %K proterozoic %K reactivation %K Southwestern U.S. %K strain %K structural analysis %K Structural geology 16 %K synclines %K tectonics %K Tusas Mountains %K United States %K upper Precambrian %K zoning %X 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. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 34 %P 180 - 180 %8 2002/10/01/ %@ 00167592 %G eng %U 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 %N 66 %! Abstracts with Programs - Geological Society of America %0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 1989 %T Ground truth? Relationship between lineaments and bedrock fabric %A Stephen B Mabee %A Hardcastle, Kenneth C. %A Donald U Wise %K #StaffPubs %K aerial photography %K BEDROCK %K fabric %K faults %K fractures %K granites %K ground truth %K igneous rocks %K joints %K lineaments %K Maine %K orientation %K pegmatite %K plutonic rocks %K quartz veins %K SLAR %K structural analysis %K Structural geology %K Structural geology 16 %K United States %K veins %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 21 %P A68 - A68 %8 1989/01/01/ %@ 00167592 %G eng %N 66 %! Abstracts with Programs - Geological Society of America %0 Conference Proceedings %B Abstracts with Programs - Geological Society of America %D 2011 %T Identifying and examining potential geothermal resources in non-traditional regions, examples from the northeastern U.S. %A Koteas, G. Christopher %A John Michael Rhodes %A Stephen B Mabee %A Goodhue, Nathaniel %A Adams, Sharon A. %K #StaffPubs %K Andover Granite %K Eastern U.S. %K Economic geology, geology of energy sources 29A %K exploitation %K exploration %K Fall River Granite %K field studies %K geochemistry %K geothermal energy %K identification %K mapping %K massachusetts %K models %K Northeastern U.S. %K overburden %K resources %K sampling %K southeastern Massachusetts %K spectra %K structural analysis %K technology %K temperature %K United States %K whole rock %K X-ray fluorescence spectra %X The search for geothermal resources is rapidly expanding into tectonic regions that have not been previously considered to be suitable for exploitation. Many of these regions, such as the northeastern U.S., have never been the site of extensive geophysical investigations and have few deep borehole temperature measurements. Nevertheless, large portions of the northeastern U.S. are underlain by granitic bedrock that may be a productive energy source by applying enhanced geothermal technologies. In the absence of traditional reconnaissance data, we utilize field studies and sampling together with geochemical analysis to develop models of geothermal resources that can be tested against data from deep boreholes. Heat production is calculated from the measured density of the samples, the concentrations of K, U, and Th from whole-rock geochemical analysis via X-ray fluorescence, and established radiogenic heat production values. Models for a particular area can then be generated by calculating depth-specific temperatures using heat production, measured thermal conductivity for each sample, and assumptions related to local stratigraphy and regional heat flow. Mapping and structural extrapolation are used to establish the subsurface characteristics at a study site and are combined with the thermal and chemical characteristics of contact rocks and overburden materials. Two examples of the application of this technique are the Fall River granite at the margin of the Narragansett Basin in southeastern Massachusetts and the Andover Granite in northeastern Massachusetts. Thermal models of the Fall River Pluton indicate average temperatures of 71 degrees C at depths of 4 km and 97 degrees C at 6 km. Average temperatures increase to 107 degrees C and 132 degrees C, respectively, when a 2 km thick sediment package is modeled overlying the granite. The Andover Granite, which is not associated with a sedimentary basin and is in a more structurally complex configuration, yields an average temperature of 74 degrees C at a depth of 4 km and 101 degrees C at 6 km. While this approach to modeling temperature-depth profiles requires some regional heat flow assumptions, the application of mapping and structural analysis with geochemistry and thermal conductivity studies can be an important reconnaissance tool for identifying non-traditional geothermal resources. %B Abstracts with Programs - Geological Society of America %I Geological Society of America (GSA) : Boulder, CO, United States %C United States %V 43 %P 40 - 40 %8 2011/10/01/ %@ 00167592 %G eng %N 55 %! Abstracts with Programs - Geological Society of America %0 Journal Article %J Journal of Structural Geology %D 2008 %T Influence of rock fabric on fracture attribute distribution and implications for groundwater flow in the Nashoba Terrane, eastern Massachusetts %A Alex K Manda %A Stephen B Mabee %A Donald U Wise %K #StaffPubs %K foliation %K fractures %K ground water %K Hydrogeology 21 %K joints %K massachusetts %K movement %K Nashoba terrane %K preferred orientation %K statistical distribution %K structural analysis %K Structural geology %K style %K terranes %K United States %X Attributes (i.e. trace-length, spacing, termination and orientation) of joints and foliation-parallel fractures (FPFs) are used to assess the influence of lithology and fabric on fracture type and distribution in metamorphic and igneous rocks of the Nashoba terrane, Massachusetts. Orientations of NE-SW and NW-SE trending joints are consistent throughout the region, whereas FPFs are sub-parallel to the axis of the terrane. Joint spacing generally decreases to the northeast across the terrane reflecting lithologic changes from metamorphic to igneous rock types. Although trace-length and spacing frequency distributions of both joints and FPFs are best described by lognormal functions, FPFs possess narrower fracture spacing than joints. Median fracture trace-lengths of all FPFs are comparable to those of all steep joints, but the median fracture spacing is half that of all steep joints. Trace-lengths of FPFs vary as a function of the degree of development of foliation. Fracture attributes and groundwater flow models suggest that FPFs may significantly increase fracture connectivity and potential for groundwater recharge. FPFs may account for as much as 30% of flow in fracture networks suggesting that in addition to joints, FPFs play a significant role in groundwater hydraulics that may include imparting flow anisotropy on the groundwater system. %B Journal of Structural Geology %I Elsevier : Oxford, International %C International %V 30 %P 464 - 477 %8 2008/04/01/ %@ 01918141 %G eng %U http://www.sciencedirect.com/science/article/pii/S0191814107002362 %N 44 %! Journal of Structural Geology