The usage of biotite as an exploration vector in igneous systems, as exemplified for the 1.54 Ga Salmi batholith, Russian Karelia.
0
Citation
0
Reference
10
Related Paper
Keywords:
Batholith
Batholith
Cite
Citations (0)
Batholith
Cite
Citations (0)
Biotite micas from igneous rocks differ from one another mainly in their contents of SiO 2 , Al 2 O 3 , MgO, total Fe as FeO and, to a less extent, in TiO 2 . The variation in amount of each of these oxides was investigated. It was found that some depend on the nature of minerals associated with the biotite, others on the general nature of the rock containing the biotite.
Paragenesis
Cite
Citations (137)
Amphibole
Massif
Fluorine
Cite
Citations (14)
Originally prepared for the GSA Thompson Field Forum that ran from Terrace to Prince Rupert, British Columbia, this guide describes the geology along the Skeena River transect of the Coast Mountains batholith, the largest Cordilleran batholith of western North America and one of the largest continental-margin batholiths in the world. The last guide to this area was published in 1983 and this new volume is the only modern overview of the last decades of work. The authors use the transect as a basis to examine the growth of the Coast Mountains batholith as a whole, emphasizing commonalities and variations with the batholith and how these traits may reflect magmatic processes that create convergent-margin batholiths.
Batholith
Continental Margin
Cite
Citations (2)
Abstract Thirty biotite and two muscovite ages are reported from thirteen plutons in the Berridale Batholith, a thoroughly mapped composite batholith in southeastern Australia. Middle Ordovician country rocks place an older limit on the age of the batholith. The mica ages of samples from any one pluton agree within experimental error except in a few cases where later plutons caused metamorphic resetting. Significant age differences have been found between plutons. The mica ages are consistent with the mapped intrusive sequence and range between 420 m.y. and 429 m.y., which indicates cooling of the intrusives to the biotite blocking temperature of about 300°C during the Late Silurian and Early Devonian. The agreement between the muscovite and biotite ages and also one age from a total rock with high Rb/Sr suggests that this cooling interval was short.
Batholith
Muscovite
Devonian
Cite
Citations (74)
ABSTRACT The Peninsular Ranges Batholith of southern and Baja California is the largest segment of a Cretaceous magmatic arc that was once continuous from northern California to southern Baja California. In this batholith, the emplacement of igneous rocks took place during a single sequence of magmatic activity, unlike many of the other components of the Cordilleran batholiths which formed during successive separate magmatic episodes. Detailed radiometric dating has shown that it is a composite of two batholiths. A western batholith, which was more heterogeneous in composition, formed as a static magmatic arc between 140 and 105 Ma and was intrusive in part into related volcanic rocks. The eastern batholith formed as a laterally transgressing arc which moved away from those older rocks between 105 and 80 Ma, intruding metasedimentary rocks. Rocks of the batholith range from undersaturated gabbros through to felsic granites, but tonalite is the most abundant rock throughout. Perhaps better than elsewhere in the Cordillera, the batholith shows beautifully developed asymmetries in chemical and isotopic properties. The main gradients in chemical composition from W to E are found among the trace elements, with Ba, Sr, Nb and the light rare earth elements increasing by more than a factor of two, and P, Rb, Pb, Th, Zn and Ga showing smaller increases. Mg and the transition metals decrease strongly towards the E, with Sc, V and Cu falling to less than half of their value in the most westerly rocks. Oxygen becomes very systematically more enriched in 18 O from W to E and the Sr, Nd and Pb isotopic systems change progressively from mantle values in the W to a more evolved character on the eastern side of the batholith. In detail the petrogenesis of the Peninsular Ranges Batholith is not completely understood, but many general aspects of the origin are clear. The exposed rocks, particularly in the western batholith, closely resemble those of present day island arcs, although the most typical and average tonalitic composition is distinctly more felsic than the mean quartz diorite or mafic andesite composition of arcs. Chemical and isotopic properties of the western part of the batholith indicate that it formed as the root of a primitive island arc on oceanic lithosphere at a convergent plate margin. Further E, the plutonic rocks appear to have been derived by partial melting from deeper sources of broadly basaltic composition at subcrustal levels. The compositional systematics of the batholith do not reflect a simple mixing of various end-members but are a reflection of the differing character of the source regions laterally and vertically away from the pre-Cretaceous continental margin.
Batholith
Felsic
Back-arc basin
Cite
Citations (258)