Most of the organic nitrogen (Norg) on Earth is disseminated in crustal sediments and rocks in the form of fossil nitrogen-containing organic matter. The chemical speciation of fossil Norg within the overall molecular structure of organic matter changes with time and heating during burial. Progressive thermal evolution of organic matter involves phases of enhanced elimination of Norg and ultima...

Study of the concentration and isotopic composition of strontium and rubidium in hornblende diorite dikes and sills of Precambrian age from the Panamint Mountains of California showed that these rock systems were enriched in radiogenic Sr during a late Mesozoic metamorphism. Enrichments in radiogenic Sr were observed for total-rock samples which yielded apparent ages of up to 34,000 m.y., altho...

Recent work in Barrovian metamorphic terranes has found that rocks experience peak metamorphic temperatures across several grades at similar times. This result is inconsistent with most geodynamic models of crustal over-thickening and conductive heating, wherein rocks which reach different metamorphic grades generally reach peak temperatures at different times. Instead, the presence of addition...

The Dora-Maira massif is an archetypal nappe stack of subducted and exhumed upper crust. Slices continental crust experienced metamorphism at blueschist to ultrahigh-pressure (UHP) eclogite-facies conditions. While the timing peak in UHP unit has been extensively studied, little known about other units. In order constrain conditions high-pressure metamorphism, U-Pb-trace element analyses rutile...