5:15 PM - 6:30 PM
[BPT05-P12] Stratigraphy of banded iron formation in El Dabbah, Eastern Egypt
Keywords:banded iron formation, Neoproterozoic
The El Dabbah area has been divided into four geological sections by a left-lateral fault (N-S strike) and reverse fault (E-W strike). In the northeast and northwest areas, volcaniclastic rocks are deposited horizontally, which include thin BIF in the northwest area. In addition, this area is covered unconformably by the Hammamat Group which is a continental sedimentary succession showing a dome-like fold structure. In the southeastern area, the main rock types are gabbro, massive basalt and coarse-grained volcaniclastic rocks. BIF are randomly occurs in several places. In the southwest area, coarse-grained volcaniclastic rocks, pillow lava, black shale and BIF make alternating layers. Strata are mostly dipping to the north at around 40-60 degrees. In the southwest area, gabbro and thick lava mainly comprises the basement. In the central unit of the southwest area, the continuity of stratigraphy is preserved, and BIF and black shale are interbedded with pillow lava and volcaniclastic rocks.
Our study focused on two well-preserved areas. We performed XRF and REE chemical analysis for powdered rock samples from both areas. We also analyzed Corg and δ13Corg of black shales overlying BIF at the other section. Corg is 0.07 ~ 0.12 wt % and δ13Corg is -22.5 ~-23.5 ‰. Trace elements in volcaniclastic rocks around the BIF are indicative of a volcanic arc basalt origin in terms of a Nb−Zr−Y discrimination diagram. The volcanic rocks consist of sparsely vesicular pillow and massive lavas, and sediments of continental origin are not present except for the BIF and black shale. In conclusion, these formations were likely formed near island arc setting. BIF of this area was deposited repeatedly during a resting stage of the volcanic activity.