Transcript ppt, 404KB - RCL-CORTEZ Workshop

Magmatism and
Deformation
•
•
•
•
•
•
•
•
Luca Ferrari
Phil Gans
Chris Henry
Allen Glazner
Andy Barth
Ian MacMillan
Martin Wong
Axel Schmitt
What we think we know
• Significant volcanism accompanied rifting
• Gulf underwent “arc” volcanism preceding rifting
• An “arc” signature does not necessarily indicate that
subduction was active
• Volcanism accompanied rifting (perhaps more than realized)
– Outside of Baja, these rocks have scarcely been studied
• In Guaymas segment of mainland, volcanic episodes
preceded deformation episodes
• Gulf and Walker Lane broke at eastern edge of regions
where crust is almost entirely coarse-grained (but quartzrich) plutonic rocks
– Rifting and deformation may avoid batholiths; Sierra Nevada, PRB,
SMO)
What we would like to know
• What were magma generation processes?
– Pre- vs. syn- vs. post-rift
• What are volumes of pre- and syn-rift magmatic rocks?
– Plutonic rocks largely unexposed; can geophysics help?
• Did magmatism consistently precede deformation, or vice
versa?
• How and where did magmatism modify the strength of the
lithosphere?
• What are space-time patterns of magmatism in the larger
context?
• What melted to make the magmas?
– Source, composition, P, T of mantle; crustal sources
• Are there useful xenoliths?
A project: additional
petrologic/geophysical swaths
across (and including) the Gulf
• Northern, central, and southern Gulf
• Distribution, timing, composition, and volumes of
igneous rocks
• Sedimentary record of volcanism
• Petrology to determine sources, P-T of generation,
etc.
• Geophysical studies to infer crustal structure
– Gravity, refraction, electrical methods
• Space-time variations via data compilation
• Effects of lateral variation on geodynamic modeling