ISSN:
1432-0967
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Geologie und Paläontologie
Notizen:
Abstract The marginal zone of the Mount Lowe Intrusion (MLI) is composed of a mineralogically and geochemically distinctive suite of quartz poor, alkali-enriched monzodiorites and quartz monzodiorites. Low initial 87Sr/86Sr, Rb, and Rb/Sr coupled with high Ab/Or, K/Rb, Ba and Sr suggest that feldspathic continental crust did not contribute significantly to the magma. The inferred original magma composition is most consistent with experimental data for about 20% batch modal melting of eclogite or quartz eclogite of altered oceanic tholeiite composition. The high absolute Ba and Sr abundances require in addition an enriched component, perhaps derived from dehydration processes within a subducted slab. At the level of exposure, the range of observed compositions resulted from fractionation of hornblende, plagioclase, sphene, apatite and magnetite. Fractionation resulted in formation of a peraluminous, Mn — enriched residual liquid which crystallized garnet. The grandite — enriched composition of the garnet is inferred to be due to high pressure (ca. 6.7 kb), high $$f_{{\text{O}}_{\text{2}} }$$ crystallization, relative to typical plutonic garnets. The composition of the marginal zone of MLI has many chemical similarities to early Mesozoic plutonism in the Cordilleran continental margin magmatic arc of western North America.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00373585
