Apatite groundmass

Examination of the Predynastic (ca. 5500 B.P.) bone from Tel-Roba showed the effect of contamination from the soil and solutions. Near the surface of the bone (Figure 5), the apatite groundmass is covered by kaolinite... 

Figure 5. SEM photomicrograph of Predynastic (ca. 5500 B.P.) bone found buried in the soil at Tel-Roba. Apatite groundmass of bone (A) is covered with kaolinite clay (K) and coarse subhedral grains of hematite.

Paleozoic limestone (Webb et al. 2004). These kimberlites all have similar groundmass mineralogies consisting mainly of carbonate, spinel, and serpentine with lesser monticellite, mica, apatite, and perovskite (Kong et al. 1999) and they are all of volcaniclastic facies near ground surface. Varying thicknesses of clay and fine marine sediments of the Tyrell Sea ( 4000 - 12000 years BP) and 1 to 4 m of peat overlie kimberlites (Fraser et al. 2005). Bioherms composed of coral and skeletal remains of other marine organisms sometimes outcrop. 

Aii iamprophyres have been ciassified as sannaite iamprophyres, except an uitramafic damtjernite. The sannaite iamprophyres contain kfs, amp cai, cpx, phi, ap, pi, sodaiite, ms, ttn, ep, white mica, chi, zrn, and opaque phases. The coarse-grained damtjernite consists of phenocrystic phiogopite, with groundmass caicite, aikaii feidspar, and apatite. 

The only primary phosphate mineral in the basaltic groundmass is an idiomorphic acicular apatite, which we therefore regard as the most probable primary REE carrier in the residues. However, the REE concentrations of this apatite were below the detection limit of the EDS device of our SEM. 

The presence of volatile-bearing phases such as phlogopite, apatite, and carbonates in kimberhtes testify to the volatile-rich nature of the parental magma (e.g., Mitchell, 1986). The ubiquitous serpentization present in kimberlites cannot be used as evidence of magmatic water, with the exception of groundmass serpentine that is interpreted to be primary in nature. As discussed by Mitchell (1986), there are hmited stable isotopic data consistent with a meteoric origin for some of the water in the serpentine. However, it is unclear if these results could be attributed to postemplacement exchange of deuteric serpentine with meteoric fluids. 

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