Terranes and Sutures

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Terranes and Sutures

• GEOS 425/525 2009 Lecture 18

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Formation of cont. crust
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• Also
• Helps us understand many things about regional
  tectonics
• E.g., mountain building, isotopes, strength
  heterogeneities, tectonic reconstructions, etc.

Coney et al., 1980
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Accretion may be a way for continental crust to
grow
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Terrane accretion

• Suspect terranes
• Uncertain of paleogeographical setting wrt NA for
  most of Phanerozoic
• Many apparently accreted to NA in Meso- and
  Cenozoic
• Origin of fragments? Mech of accretion?

Coney et al., 1980
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suspect terranes

• Appear exotic stratigraphically
• Commonly oceanic in character
• Boundaries are often faults
• Often paleomag is discordant

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Paleomag overview
At the time of deposition/cooling, ferromagnetic
minerals orient themselves w/mag field If not
remagnetized, preserve orientation relative to
mag field at origin - if diff than predicted mag
field, discordant

• Butler, 1992

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Colpron et al., 2007
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Cowan et al., 1997
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Paleomag model
Maxson and Tikoff, 1996

• Fault was likely a continental transform
• Near margin
• Outboard of PRB, Salinia, and Franciscan complex,
  Intermontane
• Another fault within Intermontane, to E?

Cowan et al., 1997
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• Present day config (Miller et al., 2006)

90 Ma config no trans (Miller et al., 2006)
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• Present day config

90 Ma config N option (Miller et al., 2006)
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• Present day config

90 Ma config S option (Miller et al., 2006)
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• Present day config

90 Ma config (Butler et al., 2001)
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• Present day config

247.5-120 Ma config (Dickinson, 2004)
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• Present day config

120-34 Ma config (Dickinson, 2004)
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• Present day config

Present day config (DeCelles, 2004)
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• Present day config

100 Ma config (Wyld et al., 2006)
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• Gehrels reconstruction

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SALMON RIVER SUTURE (K)
118 Ma
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SALMON RIVER SUTURE (Lund Snee, 1988, Rubey
Vol.)
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CONTINENT-CONTINENT COLLISION (Dewey, 1977)
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SUTURINGWHAT TO LOOK FOR

• An orogenic belt! -)
• Ophiolite sequences (intact or partial sheeted
  dike swarms)
• HP or ultra-HP rock assemblages
• A pre-collisional arc
• Melange or other accretionary prism (wedge)
  materials
• Contrasting geologic terranes in juxtaposition

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Complex continent-ocean geographies will produce
complex suture patterns in collisional orogens
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TIBET AN ISLAND MICRO- CONTINENT
PALEO- TETHYS NEARLY CLOSED
MAPS BY CHRIS SCOTESE
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Zhang et al., 1984, GSA Bull.,v. 95 p. 295-312
OPHIOLITE BELTS
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Zhang et al., 1984, GSA Bull., v. 95, 295-312.
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Xiao WJ, et al., 2003, Tectonics, v.
22, 6 8 1-20.
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ARC
MELANGE
GAD, 99
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Silurian(?) carbonate knocker (block) melange,
E of Linxi, Nei Mongol
U. Paleoz. melange, N Calif.
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Simplified map of Tibetan sutures (P Kapp)
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From Yin Nie, 96
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SIMPLIFIED MODEL OF TIBETAN AMALGAMATION
(ASSEMBLY)AND SUTURING
Paul Kapp, University of Arizona
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INDUS-YARLUNG-ZANGBO(TSANGPO) SUTUREGondwana
India against pre-50 Ma Asia
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Simplified map of Tibetan sutures (P Kapp)
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Tectonics, 1998, v.17, 501-519
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Tectonics, 1999, v. 18, 929-949
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MOSTLY MID-OCEAN RIDGE-TYPE BASALT
SUB-ARC GABBRO INTRUSIVE COMPLEX
HIGH GRADE MAFIC, ULTRAMAFIC RX
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http//www.geo.unibe.ch/people/zeilinger/gz_abstra
ct_06.htm
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Next week

• Continental collision
• Extension
• Plumes
• Transforms