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1 8Plate Alia - Cavity-fill deposit. This sample is typical of the thick intervals of consolidated cavity-filldeposit encountered in parts of Site 4. Angular fragments of various lithologies are set in a silty matrix.Following formation of the deposit, some of the calcareous rock fragments have partly dissolved, creatingpits and voids in the rock, and the deposit has been veined by white gypsum. Tung Chung, Site 4; DrillcoreC-13;Box6, 139.65 mPlate Allb - Cavity-fill deposit and marble. Dark blue-grey marble with white calcite veins separated byintervals of weakly consolidated cavity-fill deposit. In this case the cavity-fill deposit is dark grey andcontains assorted angular rock fragments set in a grey, silty matrix. The marble may be in situ, or it mayrepresent large detached blocks in the cavity-fill. Tung Chung, Site 4; Drillcore C-20; Box 5, 89.3 - 94.0 m76
GraniteDescriptionLight coloured, acid igneous rock composed principally of alkali-feldspar, quartz and biotite, with someplagioclase. Individual crystals in the groundmass are greater than 2 mm diameter on average. May containphenocrysts of feldspar (and quartz) in various proportions and up to about 25 mm diameter.Key diagnostic features :(i) Individual crystals are generally greater than 2 mm diameter.(ii) The mineral assemblage is dominated by quartz, alkali-feldspar and biotite, with some plagioclase.(iii) Generally massive (though locally sheared).CommentsThe granite is locally texturally heterogeneous, with abrupt variations in grain size and mineralogy. Veins ofvery coarse granite (pegmatite) and very fine granite (aplite) are observed occasionally. The freshest granitein Tung Chung drillcores has grey quartz, white feldspar and black biotite (Plate 12a). However, the biotitehas commonly altered to chlorite, giving the rock a greenish appearance. Pervasively weathered granite isstained brown (Plate 12b).Mineral and textural modifications of the granite are commonly observed in areas where it occurs close tometasedimentary rock. For example, in boreholes D-35, D-36 and D-37 in Site 5, the granite around thinintervals of metasedimentary rock has an intensely altered, 'bleached' appearance, contains small voidslined by euhedral crystals, and is mineralised by pyrite and galena. Much of the granite encountered in Site3 drillcores has a similarly 'modified' appearance, again generally in close association with metasedimentaryrock. Because of the close association with metasedimentary rocks, the modified granite has been termed'contact fades' granite (Plates 13a and 13b). It is generally pink, often contains small, primary cavities, andis rich in quartz, which occurs in the groundmass and also as discrete 'blobs' and veins.Reference sample no. : 5, 6, 25; also in Reference drillcore D-34 (120.5 - 139 m).1 8Plate A 12a - Typical unweathered granite from Site 5.Tung Chung, Site 5; Drillcore E-28; Box 3, 22.8 m11
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THE UNIVERSITY OF HONG KONGLIBRARIE
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,11 DEC'£• Government of the Hon
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CONTENTSPageTitle Page 1Foreword 3C
Page 10:
11 Location Map Showing the Distrib
Page 18 and 19:
Seismic reflection line8Onshore are
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Table 2 - Summary of the Onshore an
Page 23:
These faults offset the caldera bou
Page 27 and 28: Chapter 4Mesozoic Sedimentary and V
Page 29 and 30: Tuffite. A prominent outcrop of ban
Page 31 and 32: Lantau GraniteThe Lantau Granite is
Page 33 and 34: " .-.": •' - • • *"» JI i I
Page 35 and 36: Quartz VeinsQuartz veins are ubquit
Page 37 and 38: LEGENDOoI2PhotolineamentFaultConcea
Page 39 and 40: No. of Joints measured=82No. of Joi
Page 41 and 42: Chapter 7Metamorphism and Alteratio
Page 43 and 44: Offshore superficial deposits withi
Page 45 and 46: Plate 8 - Tung Chung Wan from the N
Page 47 and 48: Sham Wat FormationThe formation, kn
Page 49 and 50: to infill depressions and channels
Page 52: ased on recommendations contained i
Page 57 and 58: over a wider area. The survey resul
Page 59 and 60: Chapter 10Economic GeologyEconomic
Page 61 and 62: ReferencesAllen, P.M. & Stephens, E
Page 63 and 64: Li, X.C., Sewell, RJ. & Fletcher, C
Page 65 and 66: microgranite, 17, 28, 31, 32, 48 Tu
Page 67 and 68: Marine sedimentDescriptionUnconsoli
Page 73: Plate Ala- Marble. The generally da
Page 76 and 77: Plate A9 - Skarn from Site 3 showin
Page 80 and 81: Plate A12b - Pervasively weathered
Page 82 and 83: RhyoliteDescriptionAcid igneous roc
Page 84 and 85: Plate A 16a - Pervasively weathered
Page 86 and 87: 1 f < 1 9 2 OPlate A 18b - A Itered
Page 88 and 89: 2 1 2 2Plate A21 - Lamprophyric roc
Page 90 and 91: Residual soil derived from metasedi
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