Rock classification volcanic rocks

Fig. 2. Jensen cation plot for the classification of volcanic rocks in the Lac Cinquante region according to their Al, Mg, and Fe+Ti cation ratios.

Irvine T.N. Baragar, W.R.A. 1971. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 8, 523-548. 

Abstract Chronological studies of kimberlite-host rocks in the diamondiferous Buffalo Head Hills kimberlite field of north-central Alberta facilitate new interpretation of the nature, timing and sequence of kimberlite eruptions in northern Alberta. Three different emplacement episodes are recognized in association with volcanic and intrusive activity Late Cretaceous ( 88-81 Ma) Smoky Group equivalent intra- and extra-crater facies, Late Cretaceous and Paleocene ( 81 and 64 Ma) intrusion of sills or dykes, and Paleocene ( 60 Ma) Paskapoo Formation equivalent intra-crater facies. These specific periods of magmatism correspond to characteristic intra-field features such as spatial distribution, rock classification and diamond content. 

In contrast, volcanic rock classification by petrologic means is generally difficult because complete crystallization is not achieved, making it impossible to use the modal rock petrography as a classification criterion. As a result, classification of volcanic rocks has historically relied on lithogeochemistry, and the most successful approaches have employed conserved, trace element concentration ratios. These have been used as proxies for petrology to empirically classify volcanic rocks. Unfortunately, these trace elements are imperfect proxies for rock... 

Alkalis versus silica diagram used for geochemical classification of volcanic rocks. Martian meteorites, Gusev crater rocks and soils analyzed by the Spirit rover, and Bounce Rock analyzed by the Opportunity rover generally plot in the field of basalts, as does the average Mars Odyssey GRS analysis. Compositions derived from TES spectra (Surface Types 1 and 2) and the Mars Pathfinder dust-free rock plot in the basaltic andesite and andesite fields. After McSween et at. (2009). 

Fig. 1.2. Total alkali vs. silica (TAS) classification diagram of Le Maitre (1989) for representative Italian Plio-Quatemary volcanic rocks. The thick dashed line is the divide between the subalkaline and the alkaline fields of Irvine and Baragar (1971).

Fig. 1.3. AQ vs. K20/Na20 classification diagram for mafic Plio-Quatemary volcanic rocks (MgO > 4 wt %) from Italy. For explanation see text.

Fig. 2.2. A) TAS classification diagram of Tuscany magmatic rocks. Note that TAS nomenclature applies to volcanic rocks only. The dashed line divides the subalkaline and alkaline fields (Irvine and Baragar 1971). B) AQ vs. K20/Na20 diagram for mafic rocks (MgO > 3 wt%) of the Tuscany Province. For definition of AQ see Chap. 1.

Fig. 9.3. TAS classification diagram for the Sardinia Plio-Quatemary volcanic rocks.

Figure 11 Chemical classification of martian volcanic rocks. Squares show basaltic materials in the southern highlands (surface 1) and andesitic materials in the northern lowlands (surface 2), derived from deconvolved TES spectra from Mars Global Surveyor (Hamilton et al., 2001). Analyzed compositions of the Mars Pathfinder dust-free rock (Wanke et al., 2001) and martian meteorites (basaltic shergottites are filled circles and nakhlites are...

Table 1 Major groups of mantle xenoUths in kimberUte-related and alkali basalt series volcanic rocks (after Harte and Hawkeswortb, 1989). Textural classification follows that of Harte (1977). Terminology for phlogopite-rich mafic mantle xenoUths from Gregoire et al. (2002). For supplementary data and classifications see Nixon (1987), table 62. 

FIGURE 8 Plot of K20 versus Si02 for various models of bulk continental crustal composition, superimposed on the classification of calc-alkaline volcanic rocks. The model favored here is shown in the heavy black circle. A variety of other compositions have been proposed on the basis of plate tectonic models (e.g., andesite, ocean island basalt open crosses) and various seismic and geological models (open squares). These various models predict a wide range of heat-producing element abundances (K, Th, U) and thus can be tested from heat-flow data. 

Basalt classification using the Ne-Di-Ot-Hy-Q diagram Granite classification using the Ab-An-Or diagram Volcanic and plutonic rock classification using Q (F )- ANOR... 

The total The total alkalis- ilica diagram is one of the most useful classification schemes alkalis-silica available for volcanic rocks. Chemical data — the sum of the Na20 and K2O diagram (TAS) content (total alkalis, TA) and the S1O2 content (S) — are taken directly from a rock analysis as wt% oxides and plotted onto the classification diagram. 

The chemical classification and nomenclature of volcanic rocks usmg the total alkalis versus silica (TAS) diagram of Le Maitrc et al, (1989). Q. = normative quartz 01 = normative olivine. 

Fe20 /Fe0 ratios reconlmended by Middlemost (1989) for volcanic rocks, plotted according to rock type as defined in the TAS classification shown in Figure 3.1. 

The Jemm The Jensen cation plot is a classification scheme for subalkaline volcanic rocks and cation plot is particularly useful for komatiites. It is based upon the proportions of the cations (Jensen, 1976) (Fe + Fe + Ti), A1 and Mg recalculated to 100 % and plotted on a triangular... 

Middlemost E.A.K., 1989, Iron oxidation ratios, norms and the classification of volcanic rocks. Chem. Geol., 11, 19-26. 

The chemical composition of the volcanic rocks of the Ackerman and Wyatt formations in Fig. 6.14 are similar but not identical. The high concentrations of silica and the reported presence of quartz indicate that the rocks of both formations are oversaturated with respect to silica according to the classification of Shand... 

Fig. 10.15 The classification of volcanic rocks, based on their concentrations of Na O + K O and SiO in weight percent, indicates that the tuff of the Falla Formation ranges in composition from dacite to rhyolite, whereas a pebble of volcanic rock is intermediate in composition between trachyte and trachyandesite. The numbered fields are identified as follows (1) Basalt, (2) Basaltic andesite, (3) Hawaiite, (4) Mugearite and Trachybasalt, (5) Benmoreite, (6) Phonolite, (7) Phonolite tephrite, (8) Basanite and Tephrite, (9) Nephelinite, and (10) Phonolitic nephelinite. Solid circles Falla Tuff solid circle inside circle Average of four samples of tuff Cross trachyte pebble (Adapted from Wilson 1989 Faure 2001 data from Barrett et al. 1986)...

Fig. 12.14 The flows of Kirkpatrick Basalt on Pain Mesa have a wide range of silica concentrations from 49.5% to 56.0% which causes them to extend from basalt to basaltic andesite in the chemical classiflcation of volcanic rocks by Cox et al. (1979) and Wilson (1989). The chemical classification based on this diagram is in conflict with the classification based on the mineralogy of the phenocrysts on the basis of which these rocks are tholeiite basalts (Mensing 1987)...

Streckeisen, A.L. lUGS Subcommission on the Systematics of Igneous Rocks. Classification and Nomenclature of Volcanic Rocks, Lamprophyres, Carbonatites and Melilite Rocks. Recommendations and Suggestions. Neues Jahrbuch fur Mineralogie, Abhandlungen, 141 (1978) 1-14. 

Microlithofacial classification of the sandstones is based on Dott s classification modified by Pettijohn et al. (1972). They are mostly arenites and subarkose and quartz wackes (rare sublithic, sporadically lithic and arkosic). Quartz is the main component of the sandstones (about 60-70 vol. percent). Feldspars (6 vol. percent) are mostly represented by potassium feldspars with plagioclases in lesser amounts. Some micas (muscovite and biotite) and chlorites are observed. Mica content of arenites reaches 3 vol. %, but is higher in the wackes. Heavy minerals present include zircon, sphene, rutile and apatite. Magmatic rocks (volcanic more than Plutonic) are predominant among lithoclasts (about 2 vol. %), but some metamorphic and sedimentary clasts being present too. 

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