Table 7: Quantitative analysis indicating the amount of each mineral present and the extent of alterationScores |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
Colour (of thin-section to naked eye) |
Transparent, colourless | | Near opaque, very dark green | Predominant non-green colour |
Grain size (from estimates of original pyroxene average grain size) |
<0.25mm | 0.25mm | 0.375mm | 0.50mm |
0.75mm | 1.00mm | 1.50mm | 2.00mm | 4.00mm | >4.00mm |
Pyroxene alteration (visible in thin-section through x4 and x10 magnification) |
All pyroxene grains are unaltered (i.e. fresh) | Less than 50% of pyroxene grains have <5% altered | A majority of the pyroxene grains have <10% altered | All pyroxene grains have <25% altered | All pyroxene grains have between 25%-75% altered | All pyroxene grains have between 75%-95% altered | Less than 5% unaltered pyroxene | Small amounts (<5%) of unaltered pyroxene | Possible pyroxene pseudomorphs | No evidence of pyroxene |
Feldspar alteration (visible in thin-section through x4 and x10 magnification) |
Fresh, unaltered Fsp with clear cleavage and twinning | Less than 5% alteration on 50% Fsp; clear twinning evident, cleavage not apparent | All Fsp <10% altered: clear twinning evident, cleavage not seen | All Fsp between 10% to 50% altered: clear twinning evident, cleavage not seen | All Fsp between 50% to 90% altered: clear twinning evident, cleavage not seen | Less than 10% original Fsp: twinning evident, cleavage not seen | All Fsp altered, with clear ghost shape and twinning obvious | All Fsp altered, with ghost shapes and suggested twinning throughout | All Fsp altered, with ghost shapes and suggested twinning evident in few places | No evidence of Fsp |
Opaque minerals (seen in thin-section through x4 and x10 magnification) |
Coarse, angular opaque grains, >2mm | Coarse opaque grains, with alteration and skeletal structure or elongate grains >2mm | Coarse angular opaque grains with clear polygonal skeletons >2mm | Medium, angular opaque grains, 0.5mm to 2mm, with no skeletal or ladder-like lattice seen | Medium angular opaque grains, with distinctive polygonal skeleton(s) 0.5mm to 2mm | Medium angular opaque grains, with elongate/ladder-like grains 0.5mm to 2mm | Medium angular opaque grains with eroded appearance and no skeleton visible 0.5 to 2mm | Fine opaque grains <0.5mm | Opaque grains different from descriptions 1-8 | No opaque grains seen |
Amphibole and Mica (chlorite and biotite) |
No amphibole or mica seen | Primary amphibole present | Secondary amphibole present | |
Epidote |
---|
No epidote present | Very fine cloudy masses present | Distinct, small (<0.2mm) grains present | |
Apatite |
No apatite seen | Small grains (<0.1mm) present | Larger grains (>0.1mm) present or plentiful fine-grained apatite | |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |