Title: Construction, solidification and internal differentiation of a large felsic arc pluton: Cathedral Peak granodiorite, Sierra Nevada Batholith
Abstract: The Tuolumne Batholith (TB), Sierra Nevada Batholith (USA), is an archetypal large, zoned arc intrusion ( c . 1200 km 2 ). Previous work proposed that compositional zonation observed in the TB was produced in-situ by inward differentiation of a large magma chamber and/or large-scale, intrachamber magma mixing. Recent geochronology shows
that the TB was intruded over 8–9 Ma, making single pulse fractionation or mixing in a magma chamber of TB dimensions unlikely.
We examine processes responsible for compositional variation in the Cathedral Peak Granodiorite, which is the largest mapped
unit of the TB. New field, geochemical and geochronological work along a roughly contact-perpendicular 5 km transect indicates:
(1) magmatic foliation is steeply-dipping (>60°); (2) field evidence for repeated separation of crystals from melt and local
magma mixing is observed; (3) U–Pb zircon ages at opposing ends of the transect are indistinguishable within error ( c . 87.5 Ma); (4) bulk composition varies only modestly but trace elements show variable degrees of scatter; (5) eNd(t) and
87 Sr/ 86 Sr(i) have small variation compared with that in the whole TB. Geochemical and isotopic data are compatible with fractionation
of major silicates and accessory minerals. However, the geochemical spatial variation, minor isotopic variation and field
evidence suggest that fractionation was highly disorganized and also involved mixing with new input magma and remobilization
of crystal mush as the pluton solidified. Our observations are consistent with the construction of a large and dynamic magma
system within the last c . 1 Ma of TB growth.
Publication Year: 2008
Publication Date: 2008-01-01
Language: en
Type: article
Indexed In: ['crossref']
Access and Citation
Cited By Count: 39
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot