Rock Classification Scheme (BGS).pdf - The Water, Sanitation and ...

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a.15131197531Na 2O + K 2O wt%foidite(TAS)trachybasaltpicrobasalttephrite(TAS)(ol 10%)tephriphonolitephonotephritebasalt(TAS)phonolite(TAS)trachyandesitebasaliticandesiteandesite(TAS)trachyte (TAS)(q 20%)dacite (TAS)rhyolite (TAS)basalitic-trachyandesite37 41 4549 53 57 61 65 69 73 77ULTRABASIC BASIC INTERMEDIATE ACID SiO 2 Wt%45 52 63Further subdivisionsof shaded fieldstrachybasaltbasaltictrachyandesitetrachyandesiteNa 2 O – 2.O ≥ K 2 OhawaiitemugearitebenmoreiteNa 2 O – 2.O ≤ K 2 Opotassictrachybasaltshoshonitelatite (TAS)b.15131197531O 3Na 2O + K 2O wt%Ph52.5, 1461, 13.5F 48.4, 11.5 U 357.6, 11.7T45, 9.4U 2 53, 9.3S 341, 749.4, 7.3U 1S 263, 745, 557, 5.952, 5O 2S 141, 3 45, 3O 1Pc BR69, 837 41 4549 53 57 61 65 69 73 77SiO 2 wt%Figure 20a. Chemical classification and nomenclature of fine-grained crystalline rocksusing the total alkali silica (TAS) diagram (after Le Bas et al., 1986). Rocksfalling on the shaded areas may be further subdivided as shown in the tableunderneath the diagram. The line drawn between the foidite field and the basanitetephritefield is dashed to indicate that further criteria must be used to separatethese types. Abbreviations: q = normative quartz; ol = normative olivine.b. Field symbols of the total alkali silica (TAS) diagram (after Le Bas et al.,1986). The pairs of numbers are coordinates of the line intersections.44
4 Na 2 O + K 2 O wt %3foidite (TAS)basanite(TAS)tephrite(TAS)basalt (TAS)basalticandesiteandesite (TAS)picrobasalt2MgO > 18% picrite1MgO > 18% & TiO 2 > 1% meimechiteMgO > 18% & TiO 2 < 1% komatiiteboniniteMgO > 8% & TiO 2 < 0. 5%37 41 45 49 53 57 61 65Figure 22 Classification and nomenclature of 'high-Mg' fine-grainedcrystalline rocks (picrite, komatiite, meimechite and boninite) using TAStogether with wt % MgO and TiO 2 . The thick stippled lines indicate thelocation of TAS fields. From Le Maitre et al., 1989.SiO 2 wt %K 2 O wt%high-K434868, 3.1medium-K2148, 1.268,1.2low-K48, 0.345 49 53 57 61 65 69 73 77SiO 2 wt%Figure 23 Division of basalts (with SiO 2 > 48%), basaltic-andesites,andesites, dacites and rhyolites into 'low-K', 'medium-K' and 'high-K' types(from Le Maitre et al., 1989; modified after Peccerillo and Taylor, 1976).Note that 'high-K' is not synonymous with 'potassic'. The thick stippledlines indicate the equivalent position of the fields in the TAS diagram.211917151311975Al 2 O 3 wt%comenditic trachytecomenditic rhyolite0.45, 510.98, 19Al 2 O 3 >1.33Fe0+4.4Al 2 O 3
Page 1 and 2: BRITISH GEOLOGICAL SURVEYRESEARCH R
Page 3 and 4: Contents1 Introduction1.1 Principle
Page 5 and 6: 1 INTRODUCTIONThe use of computers
Page 7 and 8: tion of these rocks (Figure 2b), ha
Page 9 and 10: vi The use of 0.032 mm as an import
Page 11 and 12: to 75% are angular, in a block-bomb
Page 13 and 14: Field 3Field 4Field 5Fields 6Field
Page 15 and 16: (ii) If an accurate mineral mode ca
Page 17 and 18: Field S1 Rocks with the root name t
Page 19 and 20: esulting from the presence of macro
Page 21 and 22: still be a granite in the sense of
Page 23 and 24: increasing abundance. This usage in
Page 25 and 26: REFERENCESBELLIENI, G, VISENTIN, E
Page 27 and 28: kersantite lamp 31kimberlitekimbkom
Page 29 and 30: level 1 level 2 level 3 level 4Grou
Page 31 and 32: PhiunitsClast orcrystalsize in mm.L
Page 33 and 34: Figure 5 Classification andnomencla
Page 35 and 36: level 5 level 6 level 7HIERARCHICAL
Page 37 and 38: QquartzoliteLevel 790 90alkali-feld
Page 39 and 40: level 7 level 8HIERARCHICAL LEVELga
Page 41 and 42: Level 8duniteOI90 904040peridotitep
Page 43 and 44: level 5 level 6level 7level 8level
Page 45: QLevel 890906060alkali-feldspar-rhy
Page 49 and 50: level 5 level 6 level 7COARSE-GRAIN
Page 51 and 52: 'Old name' phl cpx leu kal melolgls
Page 53 and 54: Q = 60 - 20 Q = 20 - 5P'0-10 10-65

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