geoscience.net logo
+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Quantifying the relationships between geochemical and microtextural changes across small-scale granitic shear zones


, : Quantifying the relationships between geochemical and microtextural changes across small-scale granitic shear zones. Geological Society of America 43.5

Evidence of progressive chemical changes within deformed rocks can often be used to discern fluid-rock interactions during deformation. We used several granitic float samples of centimeter scale shear zones from the Mountain Shear Zone (MSZ), Wisconsin to assess the potential for fluid rock interactions during deformation using geochemical and petrographical methods. The rocks deformed under greenschist facies conditions without appreciable volume loss, but contain evidence for fluid-rock interactions, including sericitization of feldspar and formation of biotite from amphibole. Detailed fabric analyses across the strain gradient at the centimeter scale were conducted, complemented by petrographic analysis using ArcGIS; a Geographical Information System (GIS). This strategy allowed us to quantify photomicrographs for Grain Size Distribution (GSD), Shape Preferred Orientation (SPO), and Average Nearest Neighbor Analysis (ANNA). X-Ray Fluorescence (XRF) was used for whole rock geochemical analyses. Within quartz, deformation was largely accomplished by dislocation creep accommodated by dynamic recrystallization. Any evidence of grain-scale deformation in feldspar grains were not preserved due to sericitization. Quartz and feldspar both displayed a minor amount of grain size reduction. A prominent shape preferred orientation formed in the quartz grains with increasing strain.. We used ANNA to calculate the Nearest Neighbor Index (NNI) for mineral grains. NNI plotted as a function of strain reveals quartz and feldspar grains to be dispersed (NNI >1) regardless of strain magnitude. Biotite aggregates are dispersed in low strain zones and shift to a clustered distribution (NNI .8-.9) with increasing strain. Isocon plots show little or no chemical differences between highly deformed and less deformed samples. Detailed geochemical traverses across zones of progressive shearing, however, indicate small, but distinguishable changes in CaO, SiO2 , Fe2 O3 , and MgO concentration in some samples. Based on these observations, we hypothesize that fluids were present throughout the history of these rocks, but did not significantly affect deformation mechanisms or metamorphism.

US$29.90


Other references

Moloo, S.K.; Steiger, R.F.; Brun, R.; Boreham, P.F.L., 1971: II. The role of Glossinain the transmission of sleeping sickness. Of 6348 examples of Glossina swynnertoni Aust. from different areas examined. 10.2-14.8% were infected with trypanosomes and of 623 of G. pallidipes Aust. 8.7% were infected, but none had infections of the salivary glands indicative of mature bruc...

Spencer, T.; Biederman, J.; Wilens, T., 1998: Growth deficits in children with attention deficit hyperactivity disorder. Stimulant-associated growth deficits in children with attention deficit hyperactivity disorder (ADHD) have long been a concern. Height deficits in preadolescence have been reported, but adult heights have been reported to be uncompromised. It is p...

Tai, K.K.ung; Goldstein, S.A.N., 1998: The transmembrane domain of minK contributes directly to the conduction pathway in human cardiac IKs K+ channels. Biophysical Journal 74(2 PART 2): A345, Feb

Nespolo Massimo; Takeda Hiroshi; Ferraris Giovanni, 1998: Representation of the axial settings of mica polytypes. Acta Crystallographica, Section A: Foundations of Crystallography: art 3; Pages 348-356. 1998.

Aziz, Abdul, 2006: Differention of heterocysts in Anabaena solitaria f. Planktonica (Brunth.) Kom. Observation of filaments in the natural population of Anabaena solitaria f. planktonica (Brunth.) Kom. indicated that new heterocysts develop by the differentiation of smallest and youngest cells situated away from existing heterocysts.

Hoogstraate A.J.; Verhoef J.; Brussee J.; Ijzerman A.P.; Bodde H.E., 1992: Structure dependent enhancement by azones of peptide dgavp transport through human stratum corneum. Journal of Controlled Release 21(1-3): 211-212

Dioli, G.L., 1964: Considerations On Psychiatric Aspects Of The Jakob-Creutzfeldt Disease. Rassegna di Studi Psichiatrici 53: 222-228

Siskind, D.; Dark, F., 2016: Is it time to rethink treatment of early psychosis?. Australian and New Zealand Journal of Psychiatry: -

Scales, G.H.; Moss, R.A.; Quin, B.F., 1978: Nutritive value of round hay bales. In field trials at Winchmore (av. rainfall 750 mm/yr) wastage from round hay bales stored in (a) exposed or (b) sheltered positions was compared with (c) conventional square bales stored in a barn. DM losses were higher in (c) than (a) or (b). Fro...

Thoma, M.E.; Hediger, M.L.; Sundaram, R.; Stanford, J.B.; Peterson, C.Matthew.; Croughan, M.S.; Chen, Z.; Buck Louis, G.M., 2012: Comparing apples and pears: women's perceptions of their body size and shape. Obesity is a growing public health problem among reproductive-aged women, with consequences for chronic disease risk and reproductive and obstetric morbidities. Evidence also suggests that body shape (i.e., regional fat distribution) may be indepe...