How old is the earth radiometric dating
The plagioclase is extremely calcic by terrestrial standards, with molar anorthite contents of 94-96% (An94-96).This reflects the extreme depletion of the bulk moon in alkalis (Na, K) as well as water and other volatile elements.They range in age from about 3.16 billion years old for the basaltic samples derived from the lunar maria, up to about 4.44 billion years old for rocks derived from the highlands.Moon rocks fall into two main categories: those found in the lunar highlands (terrae), and those in the maria.Moon rocks on Earth come from three sources: those collected by the US Apollo manned lunar landings from 1969 to 1972; samples returned by three Soviet Luna unmanned probes in the 1970s; and rocks that were ejected naturally from the lunar surface by cratering events and subsequently fell to Earth as lunar meteorites.
In 1993, three small fragments from Luna 16, weighing 200 mg, were sold for US$ 442,500.
In contrast, the mafic minerals in this suite have low Mg/Fe ratios that are inconsistent with calcic plagioclase compositions.
Ferroan anorthosites have been dated using the internal isochron method at "circa" 4.4 Ga.
The geological or deep time of Earth's past has been organized into various units according to events which took place in each period.
Different spans of time on the time scale are usually delimited by major geological or period is defined by the Cretaceous Tertiary extinction event, which marked the demise of the dinosaurs and of many marine species.