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SUMMARY:Inherited lithospheric structures control arc-continent collisiona
 l heterogeneity: insights from seismic imaging - Meghan S. Miller\, The Au
 stralian National University
DTSTART:20220209T120000Z
DTEND:20220209T130000Z
UID:TALK168092@talks.cam.ac.uk
CONTACT:Florian Millet
DESCRIPTION:Eastward along the Sunda-Banda arc\, convergence transitions f
 rom subduction of oceanic lithosphere to arc-continent collision. This reg
 ion of eastern Indonesia and Timor-Leste provides an opportunity for unrav
 eling the processes that occur during collision between a continent and a 
 volcanic arc\, and can be viewed as the temporal transition of the process
  of continental collision along strike. We have collected a range of geolo
 gical\, geodetic\, seismic\, and geomorphic data to place constraints on t
 he geometry and history of subduction. Utilizing around 4 years of new bro
 adband seismic data we image the structure of the crust through to the man
 tle. Ambient noise tomography of the crust and uppermost mantle lithospher
 e shows velocity anomalies along strike and across the arc\, related to st
 ructure of the incoming Australian plate. The pattern of anomalies at dept
 h resemble the system of salients and embayments that are present offshore
  western Australia\, which formed during rifting of east Gondwana. At deep
 er upper mantle depths\, transition from oceanic subduction to continental
  collision appears reflected in new teleseismic based tomography images an
 d waveform modeling of deep focus earthquakes. These heterogeneities withi
 n the subducted lithosphere also coincide with previously identified chang
 es in the geochemistry of the arc volcanics. Results from our body wave to
 mography show continuity of the subducting slab to depths of at least 300 
 km\, with no evidence for tearing at the scale of >~50 km even in the regi
 on of arc-continent collision. Our expanded catalogue of Benioff zone seis
 micity reveals earthquakes in what was previously thought to be a seismic 
 gap (the Wetar gap). Together\, our seismic results suggest that tearing i
 s not as advanced in this region as previously hypothesized\, implying sus
 tained subduction of continental lithosphere underneath the Banda arc. We 
 suggest the tectonic evolution of this region is defined by inherited stru
 cture of the Gondwana rifted continental margin of the incoming plate. Alt
 ogether\, we suggest that this region is characterized by subduction of co
 ntinental lithosphere poised for tearing that has perhaps just initiated\,
  but with no large slab windows. Therefore\, the initial template of plate
  structure controls orogenesis and deep mantle structure.
LOCATION:ONLINE - Details to be sent by email
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