Trondhjemite

Drummond, M.S. Defant, M.J. 1990. A model for trondhjemite-tonalite-dacite genesis and crustal growth via slab melting Archean to modern comparison. Journal of Geophysical Research, 95, 21503-21521. 

Barker, F. 1979. Trondhjemite definition, environrment and hypothesis of origin, in Trondhjemites, Dacites and related rocks. F. Barker (ed.). Elsevier Scientific Publishing Co., 1-12. 

Rather than partial melts derived from in-situ anatexis (i.e., leucosomes) these veins are trondhjemitic and represent distal magmatic injections from nearby... 

Geological Setting Three mineralized districts in Canada containing trondhjemitic to tonalitic subvolcanic complexes of variable size have been iso-topically mapped Snow Lake, Manitoba (84 km ) Sturgeon Lake, Ontario (175 km ) and Noranda, Quebec (>525 km ) and one in Sweden ... 

The Guitard Brook deposit (GB) located in the northeast El is hosted by tholeiitic basalt and gabbro of the Devereaux Formation, specifically the Black Point Gabbro and associated trondhjemitic, diabasic dykes, and basaltic flows (Langton, 1993). 

In Table 3 we present our best estimate for the chemical composition of the upper continental cmst. The footnote provides detailed information on how the value for each element was derived. In general, major-element values represent averages of the different surface-exposure studies, and errors represent one standard deviation of the mean. Because two independent studies are available for the Canadian Shield, and because it appears the Canadian Shield has lower abundances of mafic lithologies and higher abundances of sodium-rich tonalitic-trondhjemitic granitic gneisses compared to other areas (see Section 3.01.2.1),... 

TTG, Archean tonalite-trondhjemite-granodiorite PRB, Peninsula Ranges Batholith GRC, Glenelg River Complex LFB, Lachlan Fold Belt Hbl, hornblende granite Crd, cordierite grantie. 

DrummondM. S., Defant M. J., and Kepezhinskas P. K. (1996) Petrogenesis of slab-derived trondhjemite-tonalite-dacite/ adakite magmas. Trans. Roy. Soc. Edinburgh Earth Sci. 87, 205 -215. 

Martin H. and Moyen J.-F. (2002) Secular changes in tonalite-trondhjemite-granodiorite compositions as markers of the progressive cooling of the Earth. Geology 30, 319-322. 

Smithies R. H. (2000) The Archean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite. Earth Planet. Sci. Lett. 182, 115-125. 

Johnston A. D. and Wyllie P. J. (1988) Constraints on the origin of Archean trondhjemites based on phase relationships of Nuk gneiss with H2O at 15 kbar. Contrib. Mineral. Petrol. 100, 35-46. 

Rapp R. P., Watson E. B., and Miller C. F. (1991) Partial melting of amphibolite/eclogite and the origin of Archean trondhjemites and tonalites. Precamb. Res. 51, 1-25. 

The mafic rocks are komatiites, basalts, gab-bros and dolerites, and the felsic rocks are both tonalite-trondhjemite-granodiorites (TTG) and granodiorite-granite-monzogranites (GGM). Analyses of galena and K-feldspar provide initial Pb isotopic compositions, as they contain little or no uranium. 

Granitoid magmas in the compositional range Tonalite-Trondhjemite-Granodiorite. These are the magmas which have built the Archaean continental crust... 

The dominant rocks of the Earth s early continental crust are the felsic magmas of the tonalite-trondhjemite-granodiorite suite, or the TTG suite, as it is known (Rollinson, 2006). Compared to average crust TTGs are more felsic, more sodic and have a lower mg-number, and are clearly different from average "andesitic" crust (Table 4.2, Fig. 4.10). This implies that the magmatic flux across the Moho has changed with time (Kemp St Hawkesworth, 2003). 

The dominant rock-types of the Archaean continental crust are those granitoids of the tonalite-trondhjemite-granodiorite (TTG)... 

Jackson, M.D., Gallagher, K., Petford, N., and Cheadle, M.J., 2005. Towards a coupled physical and chemical model for tonalite-trondhjemite-granodiorite magma formation. Lithos, 79, 43-60. 

Martin, H., Smithies, R.H., Rapp, R., Moyen, J.-F., and Champion, D., 2005. An overview of adakite, tonalite-trondhjemite-granodiorite (TTG) and sanukitoid relationships and some implications for crustal evolution. Lithos, 79, 1-24. 

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