Potassium argon dating principles techniques and applications to geochronology Eroticchat info
Chemical compositions of major and trace elements were measured in some of the Tertiary basalt samples.
Secular variation was observed in both the incompatible element concentrations and the normative compositions.
and the limited magnetic data available suggest that the correlated linear magnetic anomalies, characteristic of oceanic rifts, may have begun forming across the axis of these on-land rift systems, indicating long-term focused volcanic accretion Rifting along the on-land sections of the Red Sea and Gulf of Aden rift systems (north of the Main Ethiopian Rift (MER)), have led to formation of segmented zones of focused faulting and magmatism.
EA, Erta Ale; TA, Tat Ali; AL, Alayta; DMH, Dabbahu-Manda Hararo; MH, Manda Hararo; MI, Manda Inakir; AG, Asal-Ghoubbet; TG, Tendaho Graben.
The secular variation occurred in a similar trend before and after the volcanic hiatus of 10–25 Ma.
It is suggested that the observed secular variation in chemical compositions could be caused by differences both in degrees of partial melting and depths of magma segregation.
Austin The conventional K-Ar dating method was applied to the 1986 dacite flow from the new lava dome at Mount St Helens, Washington.
(The terminology is given in the table on the right.) For instance, with reference to the geologic time scale, the Upper Permian (Lopingian) lasted from 270.6 /- 0.7 Ma (Ma = millions of years ago) until somewhere between 250.1 /- 0.4 Ma (oldest known Triassic) and 260.4 /- 0.7 Ma (youngest known Lopingian)—a gap in known, dated fossil assemblages of nearly 10 Ma.Here we show that lavas, which erupted since ~200 ka along part of the on-land Red Sea rift system in Afar, Ethiopia, have a consistent age-progression from the rift axis outwards, indicating that axial dyke intrusion has been the primary mechanism of segment growth and that focused magmatic accretion and extension in the crust have remained stable here over this period.