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DETRITAL ZIRCON AND MONAZITE AS A TOOL FOR RETROSPECTIVE MONITORING OF THE EARTH’S CONTINENTAL CRUST EVOLUTION: CURRENT PROBLEMS AND TASKS
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Monitoring 2019, Nov 2019, Volume 2019, p.1 - 5
Abstract
The existing global U-Pb age databases for zircons and monazites from rocks and large detrital populations were jointly analysed with the large original geochemical dataset. This dataset (whole-rock geochemistry, as well as single-grain trace element composition and total Pb age-dating of both minerals) obtained for Precambrian Ukrainian Shield (USh) rock associations, modern sediments and Phanerozoic sedimentary rocks from basins of USh periphery (accumulation reservoirs of eroded upper crustal material) yielded following results: (1) Distribution of SiO2, Zr and LREE in modern sediments and Phanerozoic sedimentary rocks is caused by two factors - sedimentary differentiation and sedimentary homogenization. Second factor erects a set of local contrast maximums in distributions, which reflect composition of upper continental crust. (2) It is vital to develop specialized criteria for zircon and monazite sampling, which can be based on a principle maximum conformity of SiO2, Zr and LREE concentrations in the drainage samples to evaluated concentrations in upper continental crust. (3) Interpretation of zircon and monazite data should take into account the mass of their grains and the concentration of both minerals in the source rocks. Application of this approach would significantly enhance reliability of further continental crust evolution study.