Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

TLDR: In this paper, porewater chemistry, solid phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the Arabian Sea.

About: This article is published in Marine Geology.The article was published on 2000-09-15 and is currently open access. It has received 127 citations till now. The article focuses on the topics: Francolite & Phosphorite.

Figures

Fig. 2. Porewater profiles for BC484 BC451, BC455: phosphate, fluoride, ammonium and alkalinity. The saturation state with respect to francolite in the porewaters was calculated as IAP (ion activity product) divided by theKsp (solubility product of francolite). The shaded areas indicate saturation.

Fig. 6. Model fits (solid lines) to the profiles of porewater phosphate, organic P (equal to Pres), Fe-bound P (PFe), authigenic P (equal to PNH4Cl 1 PCFA), and the sum of these three solid phase P fractions. The horizontal dotted line indicates the depth of bioturbation. The vertical solid line in the authigenic P profiles represents the PNH4Cl 1 PCFA concentration which is not related with in situ authigenic P formation (i.e. P associated with fish debris or carbonates, easily exchangeable P, or redeposited francolite). The vertical dotted lines represent the scenario where limited francolite formation takes place (i.e.ka 1026; leaving all other parameters the same).

Table 5 Phosphate production and removal rates for BC451 and BC455 as calculated with the diagenetic P model

Fig. 3. Profiles of extracted P phases (ppm): PNH4Cl (steps 11 2), PFe (step 3), PCFA (step 4), Pdet (step 5), Pres(steps 61 7), total P, as measured after total destruction (O), and the sum of all extracted P phases (X). Note the different scales for BC484.

Table 4 Values for the fixed and fitted parameters for BC451 and BC455 as used in the diagenetic P model

Table 1 Position, water depth, sedimentation rate (v), organic carbon concentration in the top cm, oxygen concentration and bottom water temperature of the sampled boxcores

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Pii: s0025-3227(00)00083-9" ?

In this study, porewater chemistry, solid-phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the Arabian Sea. Authigenic apatite precipitation rates vary between 0. 076 and 1. 04 mmolP cm yr, and are of the same order of magnitude as reported for other high productivity areas. This observation contrasts with previous reports of only old phosphorites in this area. Model results suggest that sediment mixing is essential in promoting early diagenetic phosphogenesis.