U-Pb Zircon and Monazite Geochronology and Hafnium Isotopic Geochemistry of Neoacadian and Early Alleghanian Plutonic Rocks in the Alabama Eastern Blue Ridge, Southern Appalachian Mountains PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download U-Pb Zircon and Monazite Geochronology and Hafnium Isotopic Geochemistry of Neoacadian and Early Alleghanian Plutonic Rocks in the Alabama Eastern Blue Ridge, Southern Appalachian Mountains PDF full book. Access full book title U-Pb Zircon and Monazite Geochronology and Hafnium Isotopic Geochemistry of Neoacadian and Early Alleghanian Plutonic Rocks in the Alabama Eastern Blue Ridge, Southern Appalachian Mountains by Stanton B. Ingram. Download full books in PDF and EPUB format.
Author: Stanton B. Ingram
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 89
Get Book Here
Book Description
The Alabama eastern Blue Ridge (EBR) of the Southern Appalachian Mountains hosts a variety of felsic plutonic rocks, which intrude multiply deformed Neoproterozoic to Ordovician metasedimentary rocks. Plutons consist of two distinct suites based on geochemical composition and degree of deformation: pre- to syn-kinematic Neoacadian, low Sr/Y plutons (ca. 380-360 Ma) and late- to post-kinematic, Early Alleghanian high Sr/Y plutons (ca. 350-330 Ma). Here, I report new whole rock geochemistry, U-Pb zircon SHRIMP-RG (Sensitive High Resolution Ion Micro Probe-Reverse Geometry) ages, and Hf isotope data for 6 plutons in the Alabama EBR. Low Sr/Y plutons are predominantly biotite-muscovite granites and granodiorites and include the Rockford Granite (376.6 ± 1.5 Ma) and the Bluff Springs Granite (363.8 ± 2.9 Ma). The Enitachopco trondhjemite dike also displays a Neoacadian age of 366.5 ± 3.5 Ma. Zircon Hf isotope data from the low Sr/Y suite range from -11.2 to +2.0. These plutons are in general strongly deformed, and display geochemical characteristics consistent with mid crustal (
Author: Stanton B. Ingram
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 89
Get Book Here
Book Description
The Alabama eastern Blue Ridge (EBR) of the Southern Appalachian Mountains hosts a variety of felsic plutonic rocks, which intrude multiply deformed Neoproterozoic to Ordovician metasedimentary rocks. Plutons consist of two distinct suites based on geochemical composition and degree of deformation: pre- to syn-kinematic Neoacadian, low Sr/Y plutons (ca. 380-360 Ma) and late- to post-kinematic, Early Alleghanian high Sr/Y plutons (ca. 350-330 Ma). Here, I report new whole rock geochemistry, U-Pb zircon SHRIMP-RG (Sensitive High Resolution Ion Micro Probe-Reverse Geometry) ages, and Hf isotope data for 6 plutons in the Alabama EBR. Low Sr/Y plutons are predominantly biotite-muscovite granites and granodiorites and include the Rockford Granite (376.6 ± 1.5 Ma) and the Bluff Springs Granite (363.8 ± 2.9 Ma). The Enitachopco trondhjemite dike also displays a Neoacadian age of 366.5 ± 3.5 Ma. Zircon Hf isotope data from the low Sr/Y suite range from -11.2 to +2.0. These plutons are in general strongly deformed, and display geochemical characteristics consistent with mid crustal (
Author: Ann E. Holmes
Publisher: Geological Society of America
ISBN: 0813700396
Category : Science
Languages : en
Pages : 276
Get Book Here
Book Description
"This volume contains field guides to the 2015 GSA Southeastern Section Meeting's field trips. The guides explore geologic history and visit four regional geologic provinces--the Nashville dome, Blue Ridge, Valley and Ridge, and Cumberland Plateau"--
Author: Steven J. Whitmeyer
Publisher: Geological Society of America
ISBN: 0813712203
Category : Science
Languages : en
Pages : 824
Get Book Here
Book Description
"This Memoir focuses on 7 'turning points' that had specific and lasting impacts on Laurentian evolution: The Neoarchean, characterized by cratonization; the Paleoproterozoic and the initial assembly of Laurentia; the Mesoproterozoic southern margin of Laurentia; the Midcontinent rift and the Grenville orogeny; (5) the Neoproterozoic breakup of Rodinia; the mid-Paleozoic phases of the Appalachian-Caledonian orogen; and the Jurassic-Paleogene assembly of the North American Cordillerar"--
Author: John M. Hanchar
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 1501509322
Category : Science
Languages : en
Pages : 520
Get Book Here
Book Description
Volume 53 of Reviews in Mineralogy and Geochemistry covers the most important aspects of zircon-related research over the past twenty-years and highlight possible future research avenues. The chapters review the structure of zircon and other mineral (and synthetic) phases with the zircon structure; the minor and trace element compositions of igneous, metamorphic and hydrothermal zircons; the study of melt inclusions in zircon; experimental and natural studies of zircon saturation and the use of zircon saturation thermometry for natural rocks; cation diffusion and oxygen diffusion in zircon; the historical development of zircon geochronology from the mid-1950s to the present; ID-TIMS, SIMS and ICP-MS; the application of zircon chronology in constraining sediment provenance and the calibration ofthe geologic time-scale; other isotopic systematics; the spectroscopy of zircon, both crystalline and metamict and an atlas of internal textures of zircon.
Author: Charles Ryan Jeffcoat
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 96
Get Book Here
Book Description
Author: Kaitlyn Suarez
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Migmatites are a common rock type in the Adirondack Mountains, NY. We analyzed a single sample of biotite-garnet-sillimanite paragneiss with foliation parallel leucosome along Route 22 south of Whitehall, NY in order to determine the timing of melting using both in-situ monazite and zircon U/Pb geochronology from the restite and leucosome layers of the same rock. Monazite was analyzed via in-situ EMPA on the Ultrachron microprobe at the University of Massachusetts. Zircon was analyzed via LA-ICP-MS (in-situ and mounted mineral separates) at the LaserChron Center. Monazite analyses from the restite yielded six compositionally distinct populations with dates of 1178 ± 16, 1139 ± 4, 1064 ± 6, 1049 ± 4, 1030 ± 5, and 1004 ± 10 Ma. Yttrium and heavy REEs decrease in monazite in two steps: one dramatic drop from ca. 1150 to 1065 Ma and another between ca. 1065 and 1050, interpreted to reflect two periods of garnet growth and melting. Analyses from the restite zircon separate yielded a significant single peak near 1050 Ma. These zircon grains exhibit fir-tree sector zoning texture which is interpreted to indicate crystallization from melt. Monazite from leucosome yielded a unimodal population at ca. 1050 Ma, however, backscatter images document alteration of monazite to apatite on the edges of the grains, and abundant uranothorite inclusions. Leucosome zircon analyses yielded a ca. 1150 Ma population from cores and a 1050 Ma population from rims. Cathodoluminescence imaging reveals that the zircon rims have textures indicative of fluid alteration. The data are consistent with these rocks undergoing two periods of melting. The first event at ca. 1150 Ma may have involved a non-garnet producing melting reaction, such as muscovite dehydration-melting. The second event at 1065 Ma involved significant garnet growth, interpreted to represent biotite dehydration-melting. Subsequently, the rocks underwent hydrothermal alteration at 1050 Ma. Monazite grains with dates at 1030 ± 5 and 1004 ± 10 Ma have higher yttrium concentrations suggesting garnet breakdown and monazite growth during decompression and retrograde metamorphism. A combination of monazite and zircon dating techniques from each compositional layer is necessary to constrain leucosome-restite relationships and to accurately interpret the timing of melting from migmatites that have experienced multiple phases of melting.
Author: M.J. Flowerdew
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Author: Charles Ryan Jeffcoat
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Author: Peter J. Berquist
Publisher:
ISBN:
Category : Geological time
Languages : en
Pages : 182
Get Book Here
Book Description
Author: Carson L. Jones
Publisher:
ISBN:
Category : Geological time
Languages : en
Pages : 119
Get Book Here
Book Description
U-Pb accessory minerals in metamorphic rocks from the Ruby Range, southwestern Montana, were analyzed isotopically and chemically by microprobe techniques in order to constrain the timing of Precambrian thermotectonic events that affected the NW edge of the Wyoming craton. Dated samples represent the Cherry Creek Metasupracrustal Suite and associated pegmatites (CCMS, youngest), the Dillon quartzofeldspathic gneiss (DQG), and the Pre-Cherry Creek basement gneisses (PCCG, oldest). Undeformed bodies of pegmatite cross-cut the NE-trending fabric of the CCMS, and coexisting monazite and xenotime from the pegmatite yield crystallization ages of 1762 " 6 Ma and 1754 " 6 Ma, respectively (207Pb/206Pb upper-intercept ages reported at 95% confidence). These results constrain latest magmatism to within a ~1760 Ma time frame, while also establishing this as a minimum age for the cross-cut fabric. Metamorphic monazite in CCMS metapelites formed at 1814 " 15 and 1773 " 8 Ma, whereas monazites preserved as inclusions in CCMS garnet record a much older ~2450 Ma event (total-Pb ages reported at 95% confidence). In DQG samples that also contain ~2450 Ma monazite in garnet, matrix monazite preserves mixed ~1760-1580 Ma dates. In one DQG sample, polymetamorphic matrix monazite formed at 1784 " 57 and 2468 " 11 Ma, whereas older magmatic zircon formed at 2772 " 11 Ma. Polygenetic zircon in another DQG sample formed at both 2471 " 20 Ma (metamorphic; Th/U = 0.0-0.1) and at 2772 " 7 Ma (magmatic; Th/U = 0.5-0.7). Likewise, zircon in two PCCG samples preserves mostly 2437 " 47 and 2762 " 37 Ma ages in rims and cores, respectively, but also exhibits subordinate, inherited cores of ~3000-3500 Ma age. Indications of a ~2550-2500 Ma event in the Ruby Range are represented by a single total-Pb date of monazite (inclusion in DQG garnet) and by a population of PCCG metamorphic zircon dated at 2523 " 14 Ma (upper-intercept age). The mixed ~1760-1580 Ma dates observed for monazite in one DQG migmatite are of uncertain origin. Possible hypotheses include rifting related to the development of the Belt Basin or to younger break-up and dispersal of supercontinent Rodinia. The ~1760 Ma mineral ages date the waning phases of thermotectonism associated with the Wyoming-Medicine collision along the Great Falls tectonic zone, which spanned an ~1865-1760 Ma interval. Monazite growth ages of ~1815-1770 Ma document earlier stages of this collision. The ~2460 Ma mineral ages reflect an earlier, cryptic thermotectonic event that is temporally associated with incipient breakup of the ~2700-2500 Ma supercontinent Kenorland. The ~2550 Ma ages may record the juxtaposition of the Montana metasedimentary terrane as part of the Wyoming craton, along the NE-trending Madison mylonite zone, during terminal assembly of Kenorland. Finally, occurrences of ~2780 Ma mineral ages in the DQG record the Beartooth orogenic signature, whereas preservation of ~3000-3500 Ma zircon ages documents a Pre-Beartooth history for the PCCG basement.
