نتایج جستجو برای: zircon morphology
تعداد نتایج: 149157 فیلتر نتایج به سال:
Eclogites formed during the Eo-alpine metamorphic event are common within the ophiolitic unit of the Mulhacén complex, which forms part of the Betic Cordillera in southeastern Spain. A detailed study with cathodoluminescence (CL) images of zircon from these eclogites has revealed three types of domains, confirmed by some differences in their REE patterns and ages. There are a) igneous domains, ...
A total of 17 sphene and 45 zircon fission track ages (FTA) are reported from the Piedmont Province of Pennsylvania, Delaware, and Maryland, the Reading Prong of New Jersey, and the Newark Basin of Pennsylvania. With the exception of one sphene sample, FTA fall within a relatively restricted age range: sphene 190-217 Ma (average 199 Ma) and zircon 143-218 Ma (average 184 Ma). Near concordance o...
A mural excavated at the Neolithic Çatalhöyük site (Central Anatolia, Turkey) has been interpreted as the oldest known map. Dating to ∼6600 BCE, it putatively depicts an explosive summit eruption of the Hasan Dağı twin-peaks volcano located ∼130 km northeast of Çatalhöyük, and a birds-eye view of a town plan in the foreground. This interpretation, however, has remained controversial not least b...
Zircon (ZrSiO4) is a small mineral highly resistant to chemical changes; this robustness has led it to be used for estimating earth conditions eons ago. It has been used to date geologic events, measuring its radiogenic Pb, U and Th isotopes. The oldest dated mineral on Earth is a zircon from Australia, and its oxygen isotope value suggests Earth’s crust was cool and wet as long ago as 4.3 bill...
The Stirling Range Formation of southwestern Australia contains discoidal impressions and trace-like fossils in tidal sandstones. The various disks have previously been linked to the Ediacaran biota, younger than 600 million years old. From this unit, we report U-Th-Pb geochronology of detrital zircon and monazite, as well as low-grade metamorphic monazite, constraining the depositional age to ...
The Bi'r Umq suture zone (BUSZ) in western Saudi Arabia comprises Neoproterozoic oceanic-arc plutonic, volcanosedimentary, and ophiolitic rocks that record some of the earliest magmatic and tectonic events of the East African Orogen in the Arabian–Nubian Shield (ANS). New Nd isotopic analyses are combined with data on zircon inheritance and published isotopic studies to establish the case that ...
U-Pb analyses of zircon from ten samples of augen gneisses, eight mafic and intermediate metaigneous rocks and six metasediments from some tectonic domains along the Calabria-Peloritani Terrane (Southern Italy) contribute to knowledge of peri-Gondwanan evolution from Late-Proterozoic to Paleozoic times. All samples were equilibrated under amphibolite to granulite facies metamorphism during the ...
Rhyolite lavas and xenoliths from the Salton Sea geothermal field (Southern California) provide insights into crustal compositions and processes during continental rupture and incipient formation of oceanic crust. Salton Buttes rhyolite lavas contain xenoliths that include granophyres, fine-grained altered rhyolites (“felsite”), and amphibole-bearing basalts. Zircon is present in lavas and xeno...
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