Uniformitarian geochemical constraints on the genesis of Jordanian Tethyan phosphorites

Abstract EN

Rare earth elements (REE) and uranium data from Jordanian phosphorites can be used to deduce important conclusions concerning the process of phosphogenesis.

The behavior of these elements in the modem marine environment, be they in the water column or during sedimentation and diagenesis, must be considered in this regard.

The concentrations of REE and U in phosphorite in general and in Jordanian phosphorite in particular in relatively high compared to other authigenic sediments.

This observation can be attributed to the ease with which these elements can fit into the crystal structure of francolite (marine carbonate flourapatite).

This phenomenon can be used in determining chemical conditions prevalent during phosphogenesis.

It is probable that REE enter the phosphate during early stages of diagenesis.

The negative Ce anomaly in Jordanian phosphorite is small compared to the Ce anomaly in normal oxygenated seawater.

This is probably due to depositon in an anoxic environment.

The high uranium concentrations can be attributed to the same factor.

Based on data from modern phosphate-rich sediments, it is estimated that the phosphate in Jordan was deposited as a phosphate-rich sediment at a rate of 0.2 cm/yr and that: the total phosphate deposition rate after upgrading was about 1-2 cm/kyr.

Sedimentation rate of Jordanian phosphorite was significantly higher than other world phosphates.

It also seems that sedimentation was faster in the south of Jordan (Shidiya) than in the northern areas (Russeifa).