Crustal Signature of δ~(13)C and Nitrogen Content in Microdiamonds from Erzgebirge, Germany: Ion Mic

• 作 者: Larissa F Dobrzhinetskaya Harry W Green II Naoto Takahata Yuji Sano Korato Shirai
• 机 构: Department of Earth Sciences, University of California at Riverside, Riverside 92521, USA,Division o
• 出 处: Journal of Earth Science
• 发表日期: 2010年05期
• 关键词: diamond subduction crustal situated reservoirs quartz Germany continental metamo

The study of δ13CPDB (Pee Dee Belemnite) and nitrogen contents in 1 to 5-μm-diameter microdiamonds included in garnets from the quartz-feldspathic gneisses (Erzgebirge, Germany) was performed in situ with the Nano-scale Secondary Ion Mass Spectrometer. The results revealed that there were two stages of diamond crystallization from a C-O-H supecritical fluid rich in biogenic car-bon and diverse minor elements of crustal origin. The δ13CPDB of the Erzgebirge diamond of the first stage falls in the range-17‰ to 19‰, with an average value of-17.8‰; the average content of nitrogen is 820 ppm. Diamonds of the second stage are characterized by δ13CPDB=-21.5‰ to-25.5‰, with an av-erage value of-23.24‰; the average nitrogen content is non-homogeneously scattered from 740 ppm to 3 370 ppm among 6 diamonds situated in garnets within the same polished rock slide. Both diamond of the first stage and diamond of the second stage carbon reservoirs belong to biogenic matter, therefore confirming deep subduction of the continental crust sediments and their subsequent exhumation during the Variscan orogeny.

The study of δ13CPDB (Pee Dee Belemnite) and nitrogen contents in 1 to 5-μm-diameter microdiamonds included in garnets from the quartz-feldspathic gneisses (Erzgebirge, Germany) was performed in situ with the Nano-scale Secondary Ion Mass Spectrometer. results revealed that there were two stages of diamond crystallization from a COH supecritical fluid rich in biogenic car-bon and diverse minor elements of crustal origin. The δ13CPDB of the Erzgebirge diamond of the first stage falls in the range -17 ‰ to 19 ‰, with an average value of -17.8 ‰, the average content of nitrogen is 820 ppm. The diamonds of the second stage are characterized by δ13CPDB = -21.5 ‰ to -25.5 ‰, with an av-erage value of-23.24 ‰; Both diamond and the first stage and diamond of the second stage carbon reservoirs belong to biogenic matter, therefore c onfirming deep subduction of the continental crust sediments and their subsequent exhumation during the Variscan orogeny.