Table 6.2a - Summary of the field and petrographic characteristics of the Lamma Suite, 'I-type' Subsuite
LAMMA SUITE
'I-type' Subsuite
| UNIT | Tai Po Granodiorite | Lantau Granite |
|---|---|---|
| Colour | grey | grey |
| Rock Type | Hornblende-biotite granodiorite | hornblende-biotite monzogranite |
| Dominant texture | porphyritic medium to fine grained | porphyritic coarse to fine grained |
| Mafic minerals | hornblende, biotite | hornblende, biotite |
| Feldspar | orthoclase zoned oligoclase | microcline mesoperthite zoned oligoclase |
| Accessory minerals | zircon, titanite, apatite, allanite, Fe-oxide | zircon, allanite, titanite, Fe-oxide |
| Alkali feldspar megacrysts | common | common |
| Pluton shape | irregular | irregular |
| Area exposed (km2) | 30 | 35 |
| Mineralization | Mo | - |
Table 6.2b - Summary of the field and petrographic characteristics of the Lamma Suite, 'A-Type' Subsuite
LAMMA SUITE
'A-Type' Subsuite
| UNIT | Chek Mun Rhyolite | Chek Lap Kok Granite | Tai Lam Granite | Tsing Shan Granite |
|---|---|---|---|---|
| Colour | light grey or white | white | light grey or white | light pinkish grey |
| Rock Type | quartzphyric rhyolite | monzogranite | biotite monzogranite | biotite monzogranite |
| Dominant texture | porphyritic fine grained | equigranular fine grained | porphyritic medium to fine grained | porphyritic coarse to fine grained |
| Mafic minerals | biotite | biotite | biotite | biotite |
| Feldspar | orthoclase albite | mesoperthite albite | orthoclase albite | microcline, mesoperthite, zoned oligoclase |
| Accessory minerals | zircon, apatite | zircon, fluorite, Fe-oxide | zircon, allanite, muscovite, fluorite | zircon, allanite, monazite |
| Alkali feldspar megacrysts | absent | absent | common | common |
| Pluton shape | (dyke swarm) | circular | elliptical | elliptical |
| Area exposed (km2) | <1 | 11.5 | 80 | 40 |
| Mineralization | - | F | Mo,Pb,F,Zn,Cu,Be,W,Sn | Mo,Sn,W,F |