Two-XRD-line ferrihydrite and Fe-Si-Mn oxyhydroxide mineralization from Franklin Seamount, western Woodlark Basin, Papua New Guinea
Two-XRD-line ferrihydrite and Fe-Si-Mn oxyhydroxide mineralization from Franklin Seamount, western Woodlark Basin, Papua New Guinea
The Canadian Mineralogist (August 1999) 37, Part 4: 973-990
- atomic packing
- Australasia
- chemical composition
- crystal chemistry
- crystal structure
- ferrihydrite
- high temperature
- hydroxides
- iron ores
- manganese ores
- metal ores
- mineral assemblages
- oxides
- oxyhydroxides
- Papua New Guinea
- phase transitions
- powder method
- samples
- sorption
- TEM data
- temperature
- thermal analysis data
- Woodlark Basin
- X-ray diffraction data
- Franklin Seamount
Large deposits of Fe-Si-Mn oxyhydroxide, intimately associated with active warm springs, cover the flanks and caldera of the Franklin Seamount, and are dominated by poorly crystalline Fe oxyhydroxide, the so-called two-line ferrihydrite. EM, XRD and SAED analysis shows that this ferrihydrite consists of friable agglomerates of randomly stacked colloidal platelets or crystallites 20-80 Aa in diameter; these possess short-range order in two dimensions and highly variable specific surface-areas. DTA indicates that this ferrihydrite is very stable and does not transform to hematite until 570 degrees C. The agglomerates of pure ferrihydrite contain important amounts of Si (av. 7.5 wt.% Si) and a constant Si:Fe ratio (av. 0.45) and minor sorbed P, S and As. An average composition of (super [6]) Fe (sub 2.9) (super [4]) (Si,Fe,Al) (sub 1.3) (O,OH,H (sub 2) O) (sub 12) is suggested for the samples from Franklin Seamount.
