How old is detrital zircon?
How old is detrital zircon?
Six sandstone samples collected from the TWL Group yielded similar detrital zircon age patterns, with four distinct clusters at 2588-2305 Ma, 2100-1600 Ma, 1251-1005 Ma 995-744Ma which correspond to peak ages of 2.45 Ga, 1.80 Ga, 1.10 Ga, and 0.82 Ga, respectively.
What are detrital zircon grains?
Detrital zircons are part of the sediment derived from weathering and erosion of pre-existing rocks. Since zircons are heavy and highly resistant at Earth’s surface, many zircons are transported, deposited and preserved as detrital zircon grains in sedimentary rocks.
How can you tell how old a zircon is?
The zircon dating method uses two decay chains. As you know, radioisotopes do not decay directly into a stable state; rather they go through stages of radioactive decay until reaching a stable isotope. The two decay chains used on zircon dating are the uranium series and the actinium series.
How is discordance zircon calculated?
If, as in most SIMS datasets, you are just choosing between 206/238 and 207/206 ages, then [1 – (206/238 age)/(207/206 age)] x 100% is a reasonable way of looking at the discordance to filter the data, as several of you have suggested.
What is depositional age?
1. Introduction. The age of a sedimentary deposit is no older than its youngest constituent. This fact, and the recent proliferation of detrital geochronology data to understand sedimentary provenance, have expanded the use of maximum depositional ages (MDAs) to constrain the ages of sedimentary deposits.
What does detrital mean in geology?
1. adj. [Geology] Pertaining to particles of rock derived from the mechanical breakdown of preexisting rocks by weathering and erosion. Detrital fragments can be transported to recombine and, through the process of lithification, become sedimentary rocks.
What type of rock is zircon?
Zircon is widespread as an accessory mineral in felsic igneous rocks. It also occurs in metamorphic rocks and, fairly often, in detrital deposits. It occurs in beach sands in many parts of the world, particularly Australia, India, Brazil, and Florida, and is a common heavy mineral in sedimentary rocks.
Why is zircon good for absolute dating?
Zircon crystals are ideal for age dating because: They are commonly formed in felsic igneous rocks, such as granite. They can also be formed in metamorphic rocks. However, because the melting point of zircon is very high (800C), these processes may add on new layers to the crystal rather than completely reworking it.
How do you calculate percent discordance?
Calculation of Twin Birth Weight Discordance. A difference of 18% or greater in birth weight should prompt more intensive fetal monitoring . Birth weight discordance =(larger twin weight−smaller twin weight) / larger twin weight×100.
What are detrital particles?
What is detrital material?
From Wikipedia, the free encyclopedia. Detritus (/dɪˈtraɪ. təs/; adj. detrital /dɪˈtraɪ. təl/) is particles of rock derived from pre-existing rock through processes of weathering and erosion.
What kind of Science is detrital zircon geochronology?
Detrital zircon geochronology is the science of analyzing the age of zircons deposited within a specific sedimentary unit by examining their inherent radioisotopes, most commonly the uranium–lead ratio.
What can a detrital zircon age distribution tell you?
A detrital zircon age distribution from a sedimentary unit provides information about the sources from which the zircons were derived, and also provides a reference that can be used to determine whether the unit was a source for sediment in younger units.
Where are zircon crystals found in the world?
This study uses 13,441 new or existing U-Pb ages of zircon crystals from strata in the Lesser Himalayan, Greater Himalayan, and Tethyan sequences in the Himalaya, the Lhasa, Qiangtang, and Nan Shan–Qilian Shan–Altun Shan terranes in Tibet, and platformal strata of the Tarim craton to constrain changes in provenance through time.
Where are the detrital zircons in the Illinois Basin?
The Illinois basin ( Fig. 1) is critically located across the possible drainage from the Appalachians to the Grand Canyon; ages of detrital zircons in Mississippian sandstones there would provide an important test of the provenance.