"時間"を武器に地球を探る : 年代測定の現状と, 同位体比による地球深部の化学的環境の解明

概要

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Based on radiogenic isotopes, we can obtain information about the Earth related to time. Radiometric dating is a typical example. Due to the advanced development of current analytical techniques, radiometric ages covering the Earths entire history can be obtained with an error of less than 1%, even for a mineral crystal. However, there still remain problems to be clarified including the reliability of decay constants and the meanings of value obtained. In another approach, an isotope ratio including a radiogenic isotope can be used to clarify the evolution of the Earth. By applying multiple isotope systematics for typical volcanic rocks such as Mid-oceanic ridge basalts (MORBs) and oceanic island basalts (OIBs), we conjecture the chemical state of the Earths interior such as the degree of chemical fractionation and degassing. As an additional material used for clarifying the Earths deep interior, I demonstrate the significance of kimberlites which might reflect the state of the Earths deep interior more directly than OIBs.
2008-06-25