Identification and discrimination of altered and metamorphosed volcanic rocks using immobile elements

Abstract Altered and metamorphosed volcanic suites can be characterized in terms of magma series (alkaline, sub-alkaline) and degree of differentiation (basaltic, andesitic, etc.) using elements that are immobile (Ti, Zr, Y, Nb, Ce, Ga, Sc) during secondary alteration processes. Geochemical data on meta-volcanic suites in the greenschist, amphibolite and granulite facies have been plotted on a series of immobile-element diagrams to illustrate the method of discrimination and classification. Extrusive and high-level intrusive volcanic rocks that have undergone subsequent alteration or metamorphism, such as spilites, keratophyres, tuffs, greenstones, greenschists, ortho-amphibolites and ortho-gneisses, can be plotted. Evidence for the volcanogenic nature of the metamorphic rocks must be obtained before the diagrams (which are based on fresh volcanic rocks) can be used in a meaningful way.

[1]  J. Hallberg,et al.  The Archaean Marda igneous complex, Western Australia , 1976 .

[2]  T. H. Andel,et al.  Volcanism and metamorphism in the Mid‐Atlantic Ridge, 22°N latitude , 1968 .

[3]  A. Herrmann,et al.  Untersuchungen an spilitischen Gesteinen der variskischen Geosynkline in Nordwestdeutschland , 1970 .

[4]  J. Loeschke.  Spurenelement-Daten von paläozoischen Spiliten aus den Ostalpen und ihre Bedeutung für geotektonische Interpretationen , 1975 .

[5]  M. Ewing,et al.  Diversity and origin of abyssal tholeiite from the Mid-Atlantic Ridge near 24° and 30° North latitude , 1969 .

[6]  B. Leake,et al.  The petrochemistry of the epidiorites of the Tayvallich Peninsula, North Knapdale, Argyllshire. , 1972, Scottish Journal of Geology.

[7]  D. F. Strong.  Geochemical evolution of an Ordovician island arc of the central Newfoundland Appalachians , 1975 .

[8]  C. Graham.  Petrochemistry and tectonic significance of Dalradian metabasaltic rocks of the SW. Scottish Highlands , 1976, Journal of the Geological Society.

[9]  D. Field,et al.  The chemistry of gabbro/amphibolite transitions in South Norway , 1973 .

[10]  S. Drury.  Chemical changes during retrogressive metamorphism of Lewisian granulite facies rocks from Coll and Tiree , 1974, Scottish Journal of Geology.

[11]  J. Cann.  Spilites from the Carlsberg Ridge, Indian Ocean , 1969 .

[12]  Julian A. Pearce,et al.  Tectonic setting of basic volcanic rocks determined using trace element analyses , 1973 .

[13]  J. Winchester,et al.  Geochemical discrimination of different magma series and their differentiation products using immobile elements , 1977 .

[14]  S. Drury.  The chemistry of some granitic veins from the Lewisian of Coll and Tiree, Argyllshire, Scotland , 1972 .

[15]  M. Ewing,et al.  Metamorphism in the Mid-Atlantic Ridge near 24° and 30° N , 1971, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[16]  S. Hart,et al.  Sea floor basalt alteration: Some chemical and Sr isotopic effects , 1974 .

[17]  P. Kamp.  The Green Beds of the Scottish Dalradian Series: Geochemistry, Origin, and Metamorphism of Mafic Sediments , 1970, The Journal of Geology.

[18]  S. Hussain,et al.  Relation between trace and major element composition of the Chitaldrug metabasalts, Mysore, India, and the Archaean mantle☆ , 1973 .

[19]  A. Glikson.  Primitive Archaean element distribution patterns: Chemical evidence and geotectonic significance , 1971 .

[20]  B. Leake,et al.  The Composition and Origin of the Striped Amphibolites of Connemara, Ireland , 1960 .

[21]  P. Kamp.  Geochemistry and origin of metasediments in the Haliburton–Madoc area, southeastern Ontario , 1968 .

[22]  J. Cann.  Rb, Sr, Y, Zr and Nb in some ocean floor basaltic rocks , 1970 .

[23]  J. Hallberg.  Geochemistry of Archaean Volcanic Belts in the Eastern Goldfields Region of Western Australia , 1972 .

[24]  K. Heier,et al.  Geochemistry of high grade metamorphic rocks, Lofoten-Vesterålen North Norway , 1971 .

[25]  E. Bonatti,et al.  Metagabbros from the Mid-Atlantic Ridge at 06°N: Contact-Hydrothermal-Dynamic Metamorphism beneath the Axial Valley , 1975, The Journal of Geology.

[26]  B. F. Leonard,et al.  Progressive Metamorphism of Amphibolite, Northwest Adirondack Mountains, New York , 1962 .

[27]  C. J. Hughes.  Spilites, keratophyres, and the igneous spectrum , 1972, Geological Magazine.

[28]  J. Winchester,et al.  Magma type and tectonic setting discrimination using immobile elements , 1975 .

[29]  S. Drury.  The geochemistry of Precambrian granulite facies rocks from the Lewisian complex of Tiree, Inner Hebrides, Scotland , 1973 .

[30]  S. Hart,et al.  Ancient and modern volcanic rocks: A trace element model , 1970 .

[31]  J. Winchester,et al.  Geochemical magma type discrimination: application to altered and metamorphosed basic igneous rocks , 1976 .

[32]  G. Lees,et al.  Basic intrusions in the Ordovician of North Wales—geochemical data and tectonic setting , 1976 .

[33]  J. G. Holland,et al.  The chemistry and origin of the Lewisian gneisses of the Scottish mainland: The Scourie and Inver Assemblages and sub-crustal accretion , 1975 .

[34]  T. Vallance.  Spilitic Degradation of a Tholeiitic Basalt , 1974 .

[35]  B. Leake.  The chemical distinction between ortho- and para-amphibolites , 1964 .