現在神戸大学に滞在中のManea夫妻の講演を，以下の要領で行います．
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日時：　４月２８日（木）１３：００−１４：３０
場所：　京都大学宇治キャンパス本館E-232D　（地図の情報は末尾に）

講演者：　
　１．Marina Manea 氏（Computational Geodynamics Laboratory,
         　                Geosciences Center, UNAM, Mexico, 上席研究員；
　　　　　　　　神戸大学都市安全研究センター 客員准教授 (6月30日まで）)

　２．Vlad C. Manea 氏 (Computational Geodynamics Laboratory,
                         　Geosciences Center, UNAM, Mexico, 上席研究員;
　　　　　　　　　神戸大学都市安全研究センター 招聘研究員 (6月30日まで）)

講演内容（各３０分講演の後，まとめて質疑）：
1. Marina Manea 氏
Structure, evolution and effect of fracture zone subduction in southern Mexico

The Tehuantepec fracture zone is one of the most prominent lithospheric
structures of the Cocos Plate, yet its tectonic evolution implications
for the southern Mexican subduction zone are not well understood. Ocean
floor ages and morphostructural analysis of the fracture zone and the
surrounding ocean floor show a rather complex tectonic evolution. The
ocean floor age estimates south of the Tehuantepec fracture zone reveal
an age of ~26 Ma at the Middle America trench. A mean age difference
across the Tehuantepec fracture zone of ~7 Ma suggests that the
Tehuantepec fracture zone would be formed as a long transform fault on
the Guadalupe plate, prior to 15 Ma. The interpretation of marine
geophysical data reveals that the upper mantle beneath Tehuantepec
fracture zone is likely to undergo strong serpentinization prior to
subduction. In this study we proposed that the serpentinized
lithospheric roots beneath the fracture zone dehydrate in subduction at
depths of 180-200 km comparable with the slab depths beneath an isolated
volcanic center, El Chich (~200 km), whose origin is still debated.
This study proposed that deserpentinization of mantle lithosphere
associated with the subduction of Tehuantepec fracture zone at great
depths is likely responsible for the unusual location and singularity of
El Chich volcano in southern Mexico.

2. Vlad C. Manea 氏
Numeric modeling and geochemical signature of fracture zones subduction

For some volcanic arcs, the geochemistry of volcanic rocks erupting
above subducted oceanic fracture zones is consistent with higher than
normal fluid inputs to arc magma sources. Here we use enrichment of
boron (B/Zr) in volcanic arc lavas as a proxy to evaluate relative
alongstrike inputs of slab-derived fluids in the Aleutian, Andean,
Cascades and Trans-Mexican arcs. Significant B/Zr spikes coincide with
subduction of prominent fracture zones in the relatively cool Aleutian
and Andean subduction zones where fracture zone subduction locally
enhances fluid introduction beneath volcanic arcs. Geodynamic models of
subduction have not previously considered how fracture zones may
influence the melt and fluid distribution above slabs. Using
high-resolution three-dimensional coupled petrological-thermomechanical
numerical simulations of subduction, we show that enhanced production of
slab-derived fluids and mantle wedge melts concentrate in areas where
fracture zones are subducted, resulting in significant along-arc
variability in magma source compositions and processes.

会場は、以下の地図の27番のE棟の2階です。
http://www.kyoto-u.ac.jp/ja/access/campus/map6r_uji.html