Ken
The Papuan Fold Belt, immediately south of Porgera is an oil province
and has has been sparsely covered by reflection seismic, airborne
gravity and occasional AGG as well as MT by companies. Getting your
hands on it is another matter as the Petroleum Division in PNG works a
lot more like the US system where data brokers and acquisition companies
tend to be custodians of the data rather than the Australian like system
adopted by their wontoks in the Minerals Division. I doubt the
companies would have done any deep crustal seismic as they have enough
trouble collecting good data in the top few kms up there so the seismic
reference may be to continental scale lithospheric studies from
earthquake monitoring data. With the eye of faith and red eyes I can see
it in the detailed mag and air gravity dataset I have which extend for
>150km either side of Porgera. The screaming DB mag anomalies from the
Porgera intrusions in an otherwise featureless magnetic terrain might
have drawn my attention before any cryptic crustal structure though
There is some support for a break in the earthquake epicentre data (see
fig on p908 of Garwin's paper in the SEG 100th Anniversary vol) although
at that scale one could make their arms sore before running out of lines
they could wave at. Greg Corbett appears to get the credit for it and is
heavily referenced by Sillitoe et al in SEG SP6 but I don't have access
to any of his '94-95 AusIMM pubs to understand his reasoning. Silliotoe
shows it extending it across the Fly platform and almost to Australia. I
doubt Greg would have used any geophysics to come to his conclusions
although he may have called on it after the event if it supported his
story. Garwin shows it offsetting an ophiolite belt and its likely that
that sort of thing would have been picked up by the old BMR mappers
there in the 60s as those maps are still pretty good.
I saw something recently which questioned the nomenclature of some of
these "transfer structures" on the basis of underplating by the
Australian plate. I put it away after a quick skim intending to come
back to it one day but its not leaping out at me now and I can't recall
the details.
Cheers
Kim
On 8/8/19 8:35 pm, Ken Witherly via SEGMIN wrote:
Dear Colleagues-
I have been asked by a colleague about a known geological feature in
PNG as his group is apparently trying to understand possible analogues
elsewhere. The question relates to-
The Porgera/Mount Kare Transfer Structure. It is a deep crustal
structure that is not visible on surface but shows up in deep crustal
gravity (and possibly magnetic, seismic and MT???) inversions.
Google turns up material on mag and gravity but I have not found
anything related to seismics or MT. Any suggestions appreciated.
Regards/Ken
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