Abstract Zirconium and Hf are nearly identical geochemically, therefore most of the crust maintains near-chondritic Zr/Hf ratios ∼35–40. By contrast, many high-silica rhyolites granites have anomalously low (15–30). As zircon is primary reservoir for both Zr preferentially incorporates Zr, crystallization controls Zr/Hf, imprinting on coexisting melt. Thus, a unique fingerprint effective magmatic fractionation in crust. Age compositional zonation zircons themselves provide record thermal...

Research Article| August 01, 2009 U-Pb zircon ages from the southwestern Karoo Basin, South Africa—Implications for Permian-Triassic boundary Andrea Fildani; Fildani 1Chevron Energy Technology Company, 6001 Bollinger Canyon Road, San Ramon, California 94583, USA Search other works by this author on: GSW Google Scholar Amy Weislogel; Weislogel 2Department of Geological Sciences, University Alabama, Tuscaloosa, Alabama 35487, Nicholas J. Drinkwater; Drinkwater 3Chevron Southern African...

A regional synthesis of new and existing geologic thermochronologic data document late Cretaceous - early Cenozoic erosion, Oligocene Miocene volcanism, subsequent extension the Basin Range Province in northwestern Nevada northeastern California. Across an ∼220-km-wide region between Santa Rosa Warner Ranges, conformable sequences 35 to 15 Ma volcanic rocks are cut by only a single generation high-angle normal faults that accommodated ∼23 km total east-west (∼12%). Fission-track, (U-Th)/He,...

Precambrian rocks in the Farmington zone northeastern Utah provide important constraints on accretionary history of southwestern Laurentia because they lie at orogenic intersection Wyoming, Yavapai-Colorado, and Mojave provinces. Approximately 200 U-Pb analyses zircons from Paleoproterozoic Wasatch Mountains (Farmington Canyon Little Willow complexes) Uinta (Owiyukuts Red Creek indicate: (1) ages 2.446 ± 0.011 Ga for igneous a meta-igneous rock 2.42 youngest detrital zircon metasedimentary...

Major element, trace and isotopic data from late Cenozoic alkali basalts comprising the Cima volcanic field, southeastern California, are used to characterize basalt sources beneath this portion of Mojave Desert over past 8 m.y. The dominantly trachybasalts with element compositions similar modern ocean‐island (OIB), regardless presence or absence mantle‐derived xenoliths. In detail, can be divided into three groups based on their ages characteristics. Those <1 in age, majority those 3–5...

Research Article| March 01, 2011 Episodic intrusion, internal differentiation, and hydrothermal alteration of the Miocene Tatoosh intrusive suite south Mount Rainier, Washington Edward A. du Bray; Bray † 1U.S. Geological Survey-MS 973, Box 25046, Denver Federal Center, Lakewood, Colorado 80225, USA †E-mail: edubray@usgs.gov Search for other works by this author on: GSW Google Scholar Charles R. Bacon; Bacon 2U.S. 910, 345 Middlefield Road, Menlo Park, California 94025, David John; John 3U.S....

Trace-element analyses of zircons from ash-flow tuffs and granitic rocks in the east-central Sierran Nevada, combined with U-Pb zircon ages trace-element abundances whole rocks, allow us to interpret a shared magmatic heritage for widespread eruption assembly typical granodioritic intrusive suite. The have 5%–15% phenocrysts quartz, feldspar, biotite, amphibole, silica contents ranging 70% 74%, variable alkali but are consistently light rare-earth enriched weak negative Eu anomalies,...

Gneissic pegmatitic leucogranite forms a dominant component (>600 km3) of the midcrustal infrastructure Ruby Mountains–East Humboldt Range core complex (Nevada, USA), and was assembled modified episodically into batholithic volume by myriad small intrusions from ca. 92 to 29 Ma. This injection consists deformed sheets other bodies emplaced syntectonically stratigraphic framework marble, calc-silicate rocks, quartzite, schist, granitoids. Bodies granite coalesce around host-rock remnants,...

New interior samples of four Yamato polymict eucrites (Y74159, Y74450, Y75011, and Y75015) have been studied by electron microprobe, transmission microscope, X ray diffraction techniques, compared with several the Victoria Land eucrites. These same analysed using Rb‐Sr Nd‐Sm isotopic systematics. Several grains inverted pigeonite, blebby augite similar to those in Binda Moama, identified all Coarse‐grained mesostasis‐rich subophitic basalts, which contain Mg‐rich pigeonite (with Fe‐rich...

The Paleocene to Eocene southern Peru porphyry belt contains three significant Cu-Mo deposits at Cuajone, Quellaveco, and Toquepala. Ten new zircon U-Pb Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) ages for Cuajone Toquepala, together with published establish a magmatic history characterized by episodic events. Punctuated magmatism is distributed over approximately 13 m.y., Toquepala 8 Quellaveco 6 m.y. of the intrusions hosting or associated introduction Cu Mo show...

Research Article| March 01, 2007 Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints James F. Tull; Tull 1Department of Geological Sciences, Florida State University, Tallahassee, 32306, USA Search for other works by this author on: GSW Google Scholar Clinton I. Barineau; Barineau Paul A. Mueller; Mueller 2Department University Florida, Gainesville, 32611, Joseph L. Wooden 3U.S. Survey, MS 937, Menlo Park, California 94050, GSA...

The Ad Duwayhi gold deposit, located in the east-central part of Arabian shield, is newest discovery Saudi Arabia. Exploration to date has identified a resource greater than 1 million ounces (oz) with significant potential for expansion. Gold mineralization was closely associated, time and space, emplacement late- postorogenic, intracrustal, northwest-oriented granite body (659 ± 7 Ma) comagmatic square quartz porphyry (646 11 Ma), hypabyssal perhaps younger phase granite. Mineralization...

The Tuscarora mining district contains the oldest and only productive Eocene epithermal deposits in Nevada. is a particularly clear example of association low-sulfidation with igneous activity structure, it unusual that consists two adjoining but physically chemically distinct types deposits. Moreover, are interest because they formed contemporaneously nearby, giant Carlin-type gold within 39.9 to 39.3 Ma volcanic field, along just outside southeastern margin caldera-like Mount Blitzen...

The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant deposits, copper ± precious metal-platinum group element (PGE) gold silver that are spatially associated with Late Triassic porphyritic intrusions. district encompasses ~500 km2 although the distribution all has been laterally condensed by Mesozoic crustal contraction. Zinc, Pb, Cu production from about 90 was ~160,000 metric tons (t) (Zn >...

Abstract Thermochronologic and thermobarometric data reveal the timing, distribution intensity of thermal events associated with detachment faulting in Sacramento Mountains metamorphic core complex. In northwest Mountains, cooling rates c. 100°C Ma −1 are Late Cretaceous plutonism followed by crust conduction. Post-Late slowed to 1–6°C . Finally, region records average 38–53°C between 20 15 Ma. contrast, profile northeast is dominated syntectonic Tertiary very rapid cooling. A granodioritic...