BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Mg-silicate gels\, limestones and the opening of the South Atlanti
 c: the bizarre giant reservoirs of offshore Brazil - Prof. Paul Wright\, N
 atural Sciences\, National Museum of Wales\, Cardiff
DTSTART:20171121T120000Z
DTEND:20171121T130000Z
UID:TALK73219@talks.cam.ac.uk
CONTACT:37221
DESCRIPTION:Rifting\, volcanism and hydrothermal alteration produced one o
 f\, if not the most unusual carbonate successions seen in the geological r
 ecord. During the Aptian\, in a transitional interval of South Atlantic op
 ening\, from rift to “sag”\, vast shallow hyper-alkaline lakes formed 
 in the central South Atlantic\, extending from both margins and covering a
 t least 100\,000km2.. These lakes generated unique carbonate-silicate succ
 essions (the Barra Velha Formation and equivalents)\, up to >500m thick\, 
 which now act as the host for the multi-billion-barrel oil fields off Braz
 il and Angola. The very limited catchment geology and hydrology of these l
 akes precluded the formation of typical evaporite deposits and instead Mg-
 silicate gels formed associated with a very small range of calcite morphol
 ogies\, in part growing in the gels. The gels converted to stevensite clay
 s which later underwent congruent dissolution to produce much of the poros
 ity in the reservoirs. The resulting rock fabrics\, often visually stunnin
 g\, present a dilemma for current classifications. Thermo-dynamic modellin
 g and C & O stable isotopes support the sedimentological models\, for what
  was an extreme system lacking in analogues. However\, the biggest challen
 ges have not been the limited amount of data from these deep reservoirs an
 d their unique composition\, but the effects of “word magic”\, that is
  the (mis)use of terms in the hope their application brings understanding.
  The misuse of just two or three terms during the discovery phase has resu
 lted in an almost catastrophic misinterpretation of the reservoirs at all 
 scales.  On a positive note\, numerous\, often very specific university re
 search projects have been supported improving our knowledge of a range of 
 non-marine carbonates\, but largely irrelevant to understanding the Aptian
  lakes. 
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences\, Downing S
 ite
END:VEVENT
END:VCALENDAR