The

Newsletter of the Conunission on Large-Volume Basaltic Provinces
IA VCEI International Association of Volcanology and Chemistry of the Earth's Interior

Number 7

May 1996

Plans for the 19971AVCEI General Assembly in Puerto Vallarta, Mexico, are wellunderway. Commission on Large-Volume Basaltic Provinces (CLVBP) member
Rosaly Lopes-Gautier has spearheaded organizing a special session Remote
Sensing of Volcanoes on Earth and the Planets, which promises to be a stimulating
fusion of communities working on volcanism throughout the solar system. Timely
research results on the Ontong Java Plateau, the Parana flood basalts, and a global
compilation of dyke swarms are summarized in this issue, as are recent meetings
focusing on large-volume basaltic provinces. As always, we welcome yourcontributions to The LIP Reader, and your recruiting of interested scientists to join
the CLVBP.

IAVCEINews

LeaderMike Cof(tnInstitute for Geophysics
The University of Texas at Austin
8701 North Mopac Expressway
Austin, TX 78759-8397, USA.
Tel: 1.512.471.0429
fax: 1.512.471.8844
internet: mikec@cof(tn.ig.utexas.edu
Secretary
John Mahoney
Department of
Geology and Geophysics
School of Ocean and Earth Scienceand Technology
University of Hawaii
2525 Correa Rd.
Honolulu, HI 96822, USA.
Tel: 1.808.956.8705
fax: 1.808.956.2538
internet:
jmahoney@soest.hawaii.edu
Newsletter Production
Janelle L Berry, Lisa Gahagan
and Toni Lee MitchelllAVCEI now has a home page on the World Wide Web (WWW), which includes
information on the CLVBP. Check out
http:/ /xrfmac.lanl.gov / Heiken/ lAVCEI_home_page; comments are welcome. At
the site, please note that personal membership has been implemented in lAVCEI.
The benefits of membership are listed on the enclosed application form, andpersonal membership for all Commission members is strongly encouraged.

CLVBPNews
Large Igneous Province (UP) Initiative
LIP studies are by nature interdisciplinary, involving topics in volcanology,
petrology, geochemistry, geophysics, geochronology, oceanography, sedimentology, paleontology, paleomagnetism, climatology, geodynamics, and planetarygeology. Elucidating linkages among LIPs, mantle dynamics, and environmental
consequences presents an exciting set of challenges of widespread interest to the
Earth science community. The multidisciplinary nature of LIPs research, with thepotential for major breakthroughs in our understanding of linked Earth systemprocesses, requires a concerted initiative to coalesce, focus, and prioritize scientificthemes, resources, and facilities. Many CLVBP members have advocated establishing mechanisms to concentrate community efforts via well-coordinated national
and international programs to survey, sample, analyze, and model LIPs. Such aneffort will involve funding from governmental and industrial sources. For example, CNRS in France is considering a LIP initiative, NSF in the USA is funding
individual LIP projects, CNR in Italy has co-funded an Apticore drill hole, AGIP
and Statoil are contributing significant resources to basic LIP research, and NASA
has a history of funding extensive work in planetary volcanism.

CLVBP members are involved in develop ing national and international initiatives to study LIPs, and grassroots
support of CLVBP members and other interested geoscientists is crucial to the success of focusing resources on
LIP problems. The CLVBP solicits your thoughts in developing the strongest possible scientific rationale forfocused LIP investigations. Please send comments to any Steering Committee member. Updates will be provided in future issues of The LIP Reader.

Volume on Large Igneous Provinces
Papers for the American Geophysical Union (AGU) LIP volume are in various stages of completion, ranging
from fully camera-ready, to under revision, to in review. The AGU Press is publishing the book as part of its
Geophysical Monograph series, with a planned release date late this year.

FUMAGES Meeting
Marine geological and geophysical community input to the Future of Marine Geosciences (FUMAGES) meeting,to be held in December 1996, has been solicited via Internet by the convenors; a recent letter is available at the
LIPs World Wide Web (WWW) site (see "Commission Products and Services"). The scientific planning document that will be forged during the meeting will likely play a key role in guiding marine geological and geophysical funding priorities for the U.S. National Science Foundation over the next five to ten years. Please makeyour thou ghts known to mgfuture@brook.edu.

Steering Committee
An updated list of Steering Committee members and their addresses follows:

Nick Arndt (Univ. ofRennes, France) ................................................................................ amdt@univ-rennesl.fr
Hans Barsczus (Univ. ofMontpellier, France ............................................ barsczus@s(\jou.dstu.univ-montp2.fr
Ian Campbell (Australian National Univ., Australia) .............................................. ihcl56l@huxley.anu.edu.au
Mike Coffin (Univ. ofTexas, USA) ............................................................................. mikec@coffinig.utexas.edu
Keith Cox (University of Oxford, UK ................................................................................. trishm@earth.ox.ac.uk
Geoff Davies (Australian National Univ., Australia) ........................................................ geoff@rses.anu.edu.au
Bob Duncan (Oregon State Univ., USA .............................................................................. rduncan@oce.orstedu
Jean Goslin (Univ. of Brest, France) ....................................................................................... goslin@univ-brestfr
Chrts Harris (Univ. of Cape Town, South Africa) .............................................................. kv@geology.uct.ac.za
Chris Hawkesworth (Open Univ., UK) .............................................................................. jldryden@openac.uk
Jim Head (Brown Univ., USA) ................................................................................. head@pggipl.geo.brown.edu
Jan Hertogen (University ofLeuven, Belgium) ............................................... janhertogen@geo.kuleuvenac.beRosaly Lopes-Gautier Oet Propulsion Lab, NASA) .................................................... rlopes@jpluvs.jpl.nasa.gov
John Mahoney (Univ. of Hawaii, USA) .................................................................... jmahoney@soest.bawaiiedu
Sverre Planke (Univ. of Oslo, Norway) .................................................................. sverre.planke@geologi.uio.no
Jakob Skogseid (Univ. of Oslo, Norway) ..................................................~.......... jakob.skogseid@geologi.uio.no
Kensaku Tamak.i (Univ. ofTokyo, Japan) ...................................................................... tamaki@ori.u-tokyo.ac.jp
Dominique Weis (Free Univ. of Brussels, Belgium) ........................................................ dweis@resulb.ulb.ac.be
Dave Williams (Univ. of Alabama, USA) ................................................................ dwillia3@wgs.geo.ua.edu
Full addresses and contact numbers for the above are available over the internet, on diskette, or as
hard copy (see below) from Mike Coffin.

Recent Research Summaries
Geological Survey of North-Central Malaita:
Implications for the Ontong Java Plateau
Results of a major geological survey of north-central
Malaita undertaken between 1990 and 1995 are now
publicly available. Nine 1:50,000 scale and one
1:100,000 scale geological maps and two accompanying
geological I economic geology memoirs have been
produced. Those interested in obtaining copies of these~2

documents should contact the Director of Geology,
Ministry of Energy, Water and Mineral Resources, Water
and Mineral Resources Division, P.O. Box G37, Honiara,
Solomon Islands.
A number of researchers have collaborated with theSolomon Islands Geological Survey in this project (e.g., J.
Mahoney, C. Neal, A. Saunders, R. Duncan, M. Tejada, and
T. Babbs), and a wealth of field, structural, geo-

chemical, and geochronological data have been
produced. The chemical, Nd-Pb-Sr isotopic, and 40Ar39Ar results demonstrate that Malaitan basement
lavas are closely similar in composition and age tobasalts from drillholes on the adjacent Ontong Java
Plateau (OJP). This summary concentrates on the
structural and stratigraphic aspects of the survey.
Building on the work done by Hughes and Turner insouthern Malaita in the 1970s, we have produced amore formalized, coherent stratigraphy of the island.
The basement exposed on Malaita comprises 2-4 kmof basaltic lavas with subordinate dyke and plutonsized ferrogabbro intrusions; this sequence is termed
the Malaita Volcanic Group (MVG). The MVG isremarkable for its uniformity of composition; >97% of
the MVG is composed of tholeiitic (cpx-plag-glassopaques ±olivine) basalt sheets which vary inthickness from 80 em to 60 m. Very little intra-sheet
sediment is present, at most mrn to, rarely, 1-3 em ofcherty pelagic sediment. These observations suggest
high rates of effusion at water depths below the
carbonate compensation depth (CCD). Despite theoverall lithological homogeneity, several sub-facies ofbasalt are present, including a visually distinctive
spherulitic variety with coarse anorthitic plagioclase{±cpx) in a fine-grained groundmass. The coversequence above the MVG is 1-3 km thick; at its base isa sequence of parallel, laminated to bedded radiolarian cherts grading upwards into alternating foraminiferal limestones and cherts (the Kwaraae and Alite
formations, respectively). These formations areoverlain by a foraminiferal limestone-plus-turbiditic
mudstone sequence (the Haruta Formation). The
influx of shard-rich, probably arc-derived, turbiditic
sediment into the deep-sea pelagic depositional
environment occurred only after the Mid-Eocene.
The subsequent sedimentary unit (the Suafa Formation) consists of both deep-sea and shallow marine
sediments, and records the gradual emergence ofMalaita after about 5-6 Ma. The deep-sea pelagic
sequence was punctuated by alkalic volcanism during
the Mid-Eocene (the Maramasike Volcanic Formation)and by alnoite intrusions in the Oligocene. All of theabove units were deformed during the mid-Pliocene(4-2 Ma) and the resulting unconformity now rests
beneath a series of localised Plio-Pleistocene limestone and clastic beds, indicating a near-subaerial tosubaerial position for Malaita during these times.
The earliest structural history of the island is linked
with the emplacement of the OJP, and field observations suggest a simple, stacked plateau-basalt
sequence. From the Eocene to the Pliocene, theMalaita region underwent extension, which resulted
in graben and basin formation, and the resulting
extensional structures have controlled sediment
thickness, loci of alkalic basalt and alnoite emplacement, and even mineralisation. Only one period ofmajor compressive-transpressive deformation isrecorded on Malaita, and it appears to be bracketed
between 4 and 2 Ma. This deformation resulted in:(1) a shortening of the Malaita region of between 24 and46%; (2) a strong NW-SE (038°-218°) structural grain,with local discordance of -20° indicating NE-SW
compression/ transpression with penecontemporaneous,
predominantly sinistral strike-slip; and (3) large
asymmetrical fold structures and thrusts with predominant early NE vergence and a later stage of SW-directedbackthrusting. The basement and cover sequence are
deformed coherently; no major decollements arepresent. We interpret the large asymmetrical foldstructures as the tip regions of blind, NE-verging
thrusts; line-balanced cross sections suggest possible
detachments at depths of between 1 and 4 km beneaththe base of the sedimentary cover. The structural data
indicate a predominant NE sense of movement between
4 and 2 Ma. Offshore, recent bathymetric results fromthe SOPACMAPS cruise in 1994 reveal a number ofmajor thrust structures with a SW sense of vergence,
consistent with the final SW-directed obduction of
Malaita over the Solomon Arc. We believe that structures associated with the late stage of SW-directedbackthrusting formed since -2 Ma.
We propose an obduction model for Malaita which
involves emergence from abyssal ocean depths at -5-6
Ma, NE-directed thrusting between 4 and 2 Ma, andfinal SW-directed obduction over the Solomon Arc after-2 Ma. Recent SOPACMAPS imagery, together withother seismic and volcano-stratigraphic evidence,
implies that the edge of the OJP has been subducting
beneath the Vitiaz Trench, at least locally, since -15 Ma.
Evidence from Malaita (and other OJP-related Solomon
islands) indicates obduction of the upper parts of the
OJP continues to occur. We suggest that the OJP issimultaneously obducting and subducting; that is, it isexperiencing 11 flake tectonics~~.

contributed by Mike Petterson (British Geological Survey,
Edinburgh, UK- mgp@wpo.nerc.ac.uk)

Parana Flood Basalts
In the Early Cretaceous, the Parana Basin was the site ofone of the larger known continental magmatic events inEarth history. Basic and intermediate lavas, overlain byrhyodacites and rhyolites, form the so-called Serra Geral
Formation. The lavas, together with associated dykes
and sills intruded into the underlying sediments, form
the Parana continental flood basalt (CFB) province.
This CFB province covers an area of 1AOO,OOO km2(Figure 1), of which -80% is in SE Brazil; !5:100,000 km2 in
Paraguay; ~100,000 km2 in Argentina; and ~100,000 km2
in Uruguay. Its present volume, without considering
the likely volumes of intrusive and eroded rocks, is~800,000 km3, to which should be added the ~70,000
km3 of the African counterpart in the Tafelberg field in
Namibia (spread over an area of ~8,000 km2). Dykes
along and parallel to the Brazilian coast are observed
from Sao Paulo State to Uruguay; NW-SE dyke swarms
crop out in Paraguay and in the Ponta Grossa Arch.

3

__ ..,_...,.,.. -- ,..- -,' '.

edge of Parana
sedimentary basin

/

I

1

~ younger Mdimentary rocks~overlying laws

flood basalts
Gramado, Urubici
Esmeralda
RibeiruParanapanema
Pitan90

SOUTH

AMERICA-,' , __,_

;

_,/ I

'

~~
''

\

~.J't~l~...

± 1.4

Sarro Geral
Escarpment
\

\
\

\
\
\

\

\

\

\
\
\

',....,.._...._ ___ _AFRICA
Figure 1

Along the southern continental margin and presumably associated with the Parana CFB, basaltic sequences
covering ~,000,000 km2 may be inferred. To the northof Sao Paulo, seismic reflectors (>900 km long,land between 70 km (N) and 160 km (S) wide) indicatethat basalts dip seaward and reveal the presence ofextensional faults. SE of the Sao Paulo Plateau reflectors dip toward the continent, suggesting that they
originated on the Angolan margin at the initial stagesof rifting, and migrated towards South America duringcontinental breakup. The boundary between the twobasaltic sequences along the continental margin
coincides with a basement fracture zone.
Although the lavas and sills are thickest {1,900 m) in
the central-western part of the Parana, the best outcrops
are found along the escarpment of the Serra Geral in
Santa Catarina and Rio Grande do Sul, from which thename of this Formation is derived. Extensive sampling
along the escarpment, compared to the rest of theProvince, biased descriptions of the general composition of the Parana CFB until borehole samples became
available for analysis. Rhyolites and rhyodacites areabundant on the escarpment and in Namibia, forming
to up 40% of the exposed sections in some areas;
however, they are not observed in the northern andwestern portions of the Parana. A similar bias, with apreponderance of data from the escarpment, alsocharacterised attempts to estimate the age and durationof magmatism by Ar-Ar analyses and sequential
palaeomagnetic data, while Rb-Sr mineral isochrons onrhyolites NW of the escarpment yielded older dates.
Ar-Ar ages on samples from across the province, andfrom boreholes subsequently demonstrated that Parana
lavas were erupted from 138-128 Ma, although any
changes in eruption rates within this period are still
being investigated.
Regional variations in the compositions of the lavas
indicate that different sources and mechanisms havebeen involved in magma production. There is amarkedly bimodal distribution in silica along the SE
escarpment, but is insignificant to the north and west in
Sao Paulo State, where the high silica rocks are <1% of
the effusive component. Ti~ contents also vary
regionally, with the rocks in the north and northwest
having relatively high Ti~ abundances compared withthose in the south and southeast. The radiogenic
isotope ratios of the low-Ti rocks are "enriched,"
apparently reflecting both assimilation and contamination within the crust, and old incompatible elementenriched source regions in the upper mantle. The
higher-Ti~ magmas in the north and northwest areless variable and enriched, and they have many of theisotope and trace element features of the older andmore enriched rocks from the Walvis Ridge. Most of
the basalts have low Nb and Ta abundances relative toLa, and to a lesser extent K, compared with mostoceanic basalts, suggesting that they were primarily
derived from enriched source regions in the sub-continental mantle. The exception is the Esmeralda
magma type, which is younger than the SSE rhyolites, andwhich has a much stronger oceanic compositional affinity.
Geochemical and isotope analysis on samples selectedfrom 10 boreholes, drilled along a N-S trending section,
revealed that stratigraphy of the central area differs fromthat of the escarpment. The central and northern areas,
where the sequence is thickest, consist of three mainbasaltic magma types (Pitanga, Paranapanema andRibeira}, and available data are consistent with thesemagma types being generated by different degrees ofpartial melting of similar source regions. However, themain magma type in the southern areas, the Gramado, isvery different: it has been affected more by crustal
contamination processes, and it appears also to have been
derived from an old enriched source region characterised
by relatively high Rb / Sr and low U / Pb ratios. The othertwo southern Parana magma types are unrelated; thesource of the Urubici was similar to that of the high Ti02
magmas of the northern Parana, while the Esmeralda,
which was probably erupted at the time of breakup, has a
predominantly asthenospheric signature.
Mapping of the different magma types, assuming thatthey represented chronostratigraphic units, has led
workers to conclude that magmatism in the Parana
migrated northward with time. However, the increasing
number of high precision Ar-Ar ages have demonstrated
that different magma types are not chronostratigraphic.
Rather, different magma types were erupted in different
places at the same time, and some magma types are ofdifferent ages in different places. Thus, Pitanga samples
from Paraguay and the bottom of the deepest borehole
yield ages of 138.4±1.4 Ma and 137.8±0.7 Ma, significantly
older than Pitanga samples from dykes in the Ponta
Grossa Arch (134.1±1.3 Ma). The Paranapanema {137-132
Ma) overlies the Pitanga in the center and north of the
Parana, whereas the Gramado yields ages of -132±1 Ma in
southern Brazil and 129-127 Main Uruguay. These results
invalidate an earlier assumption that magma types werechronostratigraphic, and instead suggest that magmatism
migrated from the NW to the SE with time. Moreover, theoverall duration of magmatism within the Parana would
appear to be 10 m.y., in contrast to the short eruption
periods inferred for many other CFBs. The observationthat different magma types were generated from different
source regions over relatively long periods of time may beconsistent with models in which the magmas are largely
produced by conductive heating of heterogeneous andvolatile-bearing mantle lithosphere.
Although the duration of magmatism is perhaps anorder of magnitude longer than those inferred for other
CFB provinces, the extrusion rate within the Parana varies
both geographically and with time. On the basis of 55
40
Ar-39Ar laser spot isochrons with MSWD <2, and on the
total preserved volume of lavas, eruption rates appear tohave reached their climax between 133 and 131 Ma, as
exemplified by rocks on the SE escarpment. Althoughuncertainties in such calculations are still considerable, estimated eruption rates increase from ~.03
km/yr between 138 and 135 Ma, to >0.13 km/yr
between 135 and 133 Ma, to ~.21 km/yr between
133 and 131 Ma. Geographically, in theN and NW,
the lower 300-1300 m of basalts were erupted in -5
m.y., whereas the overlying 600 m were emplaced in-1 m.y. Intercalation ofthick (<10m) sand dunes
between flows is an indication of long periods ofquiescence, and therefore consistent with Ar-Ar
results.

E-W transects of deep boreholes with geochemical profiles;(3) more precise estimates of the erosion history; (4) combined marine and continental data analysis; (5) deep seismic
E-W transects at different latitudes.

contributed by Marta S.M. Mantovani (IAG-USP, Siio
Paulo, Brazil-marta@iag.usp.br & http://www.usp.br/iag/
geofisica)

Diabase (Dolerite) Dyke Swarms of the World: First
Edition, 1996

Available data are consistent with the presence of a
Information from the literature on swarm geometry, geochrothermal anomaly (plume) under South America while nology, and key references for more than 500 diabase
W Gondwana was moving NW, and with extensional (dolerite) dykes from around the world is displayed on a
deformation across the Ponta Grossa dyke swarm.
1:35,000,000 scale map and catalogued in a companion
report. This compilation has so far facilitated the identificaEarly magmatism was characterised by small
amounts of extension, and hence relatively lowtion of nearly thirty giant radiating dyke swarms, the focal
eruption rates, whereas later magmatism waspoints of which are interpreted to locate mantle plumeaccentuated by the onset of extension across thecenters at the time of dyke emplacement.
proto-South Atlantic, which resulted in higher
eruption rates and large volumes of silicic rocks. The The map and report (104 pp.), by R.E. Ernst, K.L. Buchan,abnormally thick lithosphere, which may have caused T.D. West, and H.C. Palmer, appear in Geological Survey oflong periods of quiescence, lengthened formation of
Canada Open File 3241. Pricing differs within and outside
the Parana CFB province. The uplifted area, highly
Canada. Both map and report may be obtained from theeroded in the Ponta Grossa Arch, is indicative ofGeological Survey of Canada Bookstore, 601 Booth St.,
magmatic underplating, while the lower but also
Ottawa, Ontario KIA OE8. Telephone 1.613.995.4342.
eroded topography of the Rio Grande Arch suggests
Facsimile 1.613.943.0646. Internet:
more plastic crustal thinning. Furthermore, westward gsc_bookstore@gsc.emr.ca
tilting observed for the whole basin appears to be a
response to the basaltic load over a major lithospheric contributed by Richard E. Ernst (Geological Survey of
weakness (ancient plate boundary?), which isCanada-rernst@gsc.emr.ca)
supported by the gravity signature in the area.
Summaries of recent research programs are invited; please
Future priorities to refine the general view above
send your contribution to Mike Coffin or John Mahoney. For
include: (1) detailed stratigraphy of the transitional
the sake of brevity, references are omitted; please contact thearea between northern and southern provinces; (2)contributors directly for more information.

PREVIOUS MEETINGSDECCAN'96 Workshop, Mahabaleshwar, India,
26-30 January 1996

Thirty scientists and students from India, USA, UK, Italy,
Russia, and Norway participated, allowing group discussions to be focused, interactive, and lively. The workshop
included oral presentations by 29 invited speakers and field
This workshop was organized by K.V. Subbarao
trips in the Western Ghats along the Bombay-Mahabalesh(Indian Institute of Technology [liT], Powai) and G.
war-Punetransect. Technical sessions took place at IITSen (Florida International U., Miami) to 1) assess the
Powai, the Mahabaleshwar State Guest House, and thecurrent state of knowledge on the Deccan Traps; 2)
University of Pune. K.G. Cox (Oxford) delivered theevaluate priorities in Deccan research; and 3) form
inaugural address, drawing attention to the significance of
informal working groups to collaborate on specificpicritic lavas in the Deccan and West's seminal contributions
research areas. The workshop was dedicated to thememory of William D. West, who made outstanding to understanding these unusual flows. The presentations
covered a broad range: geomorphology, geophysics
contributions to Deccan Trap petrology, first as
director of the Geological Survey of India and later as (seismology, gravity, magnetostratigraphy, tectonics),
geochemical stratigraphy and petrology, and the atmoan academic who established the Geology Departspheric impact of flood basalt volcanism.
ment at Sagar University. Several Indian organizations (particularly the Geological Society of India
K.M. Storetvedt (Bergen) presented an alternative model for[GSI]) and the U.S. National Science Foundation
the evolution of the earth. P.R. Hooper (Washington State)(International Division) sponsored the workshop.

argued that extension in the Deccan lithosphereoccurred after the main eruptive event. M.R. Rampino(New York U.) presented two papers: in one, hepointed out that a giant radiating dike swarm may havesupplied Deccan magmas; in the other, he showed thatthe dates of several known flood basalt events coincidewith mass extinction events. S.A. Kuranko and A.N.
Zemtsov (Geological Institute, Moscow) discussed
magmatism in the Siberian Traps, and noted that afundamental difference between the Siberian andDeccan Traps is the presence of a thick pyroclastic layer
at the base of the Siberian flows. L. Keszthelyi and S.
Self (Hawaii) focused attention on lava flow characteristics and mode of eruption in the Columbia River
Basalt. New trace element and isotopic data bearing on
Deccan geochemical stratigraphy were presented by
S.F.R. Khadri (Vikram U.), K.V. Subbarao, and J.P.
Shrivastava (U. Delhi). A. De (Calcutta U.) argued for anear-steady-state behavior of magma chambers beneaththe eastern Deccan from phenocryst systematics andphase relationships. The effect of basement structuresin controlling eruptions and the subsequent geomorphological evolution of the Deccan landscape was the
topic of presentations by V. Kale (U. Pune}, R. Shanker
and K.S. Misra (GSI}, D.A. Sant (U. Baroda), and P.R.
Reddy (Nat'l. Geophysical Research Institute, NGRI).
T.M. Mahadevan, S.S. Rai, and U. Raval (NGRI) madeinferences from seismic tomography and gravity data
about how the Deccan plume may have interacted withthe lithosphere. Some new insight into the ages andcompositions of "post-Deccan" tholeiitic and alkalic
dikes from the west coast was provided by L. Melluso(U. Naples}, K.V. Subbarao, and A.G. Dessai (U. Goa).
There were also new reports of dioritic xenoliths (D.
Chandrasekharam, liT) from the northern Deccan andof garnet pyroxenite xenoliths from an alkalic dike near
Bombay (A.G. Dessai). K. Gopalan (NGRI) presented apaper by H.K. Gupta on the origin of the recent Latur
earthquake which killed 10,000 people. G. Sen presented a model of plume melting in which the dominant tholeiites are derived from picritic magmas
generated over a depth range of 135-85 km, whereas themuch rarer carbonatites and other alkaline magmas are
generated from the volatile-rich, cooler apron of theplume.
It became clear that very little is known about thephysical volcanology of the Deccan, and that a needexists for field measurements to explain structural
aspects of the lavas, rate of flow, flow regime, etc. S.
Self and L. Keszthelyi are taking the lead on suchmeasurements. A group at NGRI, led by S.S. Rai, isembarking on a detailed tomographic experiment toassess the nature of the sub-Deccan mantle. Moredating was considered vital, particularly of the
intrusives that occur over large areas of the Deccan;
this is being carried out by a group in Physical ResearchLaboratory (India). Geochemical and petrographic
work must be continued as well, so that a comprehensive data base of geochemical and petrographic
variations throughout the Deccan may

be produced. Sedimentological, paleontological andpalynological work on the fossiliferous beds that occur
between lavas in some places also was agreed to beimportant, to ascertain the impact of Deccan eruptions on
the local and regional ecosystem.
The perceived importance of having a centralized system
where any new information on the Deccan may be madereadily available to all interested individuals led to aconsensus to create a "Deccan page" as part of the LIPs
homepage. Printed or diskette copies would be madeavailable upon request to those who do not have Internet
access.
Some of the most enlightening discussions took place
during late beer sessions. A senior officer of the Atomic
Minerals Division (Govt. of India), whose initials are PK
but who will otherwise remain anonymous, managed tosneak in beer every evening for interested participants.
Topics in these sessions ranged rather widely-and were
not always of geological consequence-but did always
have some reference to earthly matters! Only a few
foreign and domestic participants had any trouble with theIndian food, but they were adequately equipped (medicine-wise). Perhaps the best part of the workshop was thefield trip along the Western Ghats, where the thicksequences of horizontal flows exposed led to comparisonswith the Grand Canyon, except that in the Ghats the layers
are all lava flows.
Finally, US participation almost did not happen because of
the government budget crisis and the shutdown of NSF.
M. Lueck (Program Director, INT}, with the invaluableassistance of R. Wazir (US Embassy, Delhi), went aboveand beyond the call of duty to make sure US participants
were able to attend.

contributed by Gautam Sen (Florida International
University, Miami, USA)

Scientific Konference on Intraplate, Interdisciplina
Themes (SKI-IT), Steamboat Springs, Colorado, USA
9-11 February 1996
This conference, a prelude to the U.S. National Science
Foundation-sponsored Future of Marine Geosciences(FUMAGES) meeting scheduled for December 1996,
brought together 15 scientists to define major oceanic
intraplate geoscientific problems and to discuss approaches to solving them. The dominant topic of themeeting was transfer of mass and energy from the Earth's
interior to its surface, via either plate tectonic or hot spot
processes. Four working groups addressed thematic
problems associated with these processes in the following
categories: large igneous provinces (LIPs)-M. Coffin, R.
Larson, J. Mahoney, S. Stein; hot spots-R. Duncan, J.
Orcutt, J. Phipps Morgan, P. Wessel, A. Zindler; departures from the age-dependent signal-M. McNutt, D.
Sandwell, C. Stein; intraplate deformation and plateboundary evolution- }. Austin, D. Bercovici,~
7

D. Naar. LIP themes discussed included 1) processes ofmass and energy transfer among the core, mantle, andcrust related to LIP genesis, including the origin andevolution of mantle plumes; 2) emplacement and postemplacement mechanisms and effects on the lithosphere, including plume-lithosphere-plate motion
interactions, emplacement styles, and relation to both
early and modem processes of continental growth; 3)consequences of emplacement and evolution for thehydrosphere, atmosphere, and biosphere, especiallywith respect to the carbon cycle and periods of rapid
evolutionary change.
Approaches to addressing the scientific themes thatwere considered at the conference include declassification of U.S. Navy data; better use of exisiting data;
development of an oceanic PASSCAL (Program for the
Array Seismic Studies of the Continental Lithosphere)type capability"; enhanced ocean drilling technologies*;
special initiatives*; development of new seismic
acquisition systems; implementation of an Ocean
Seismic Network (OSN); and thematic foci* (approaches of particular relevance to LIPs are indicatedby asterisks).
Conference participants are particularly grateful to M.
McNutt for oganizing the program and logisitics,
running the conference, and for assembling the final
report. Lengthy discussions within and among theworking groups were enhanced by the slopeside settingin three self-service condominiums; working, cooking,eating, socializing, bunking, and occasionally skiing
together over the three days allowed for much productive interaction. A copy of the SKI-IT report will bemade available on the CLVBP World Wide Web sitewhen ready.

contributed by Mike Coffin (University of Texas, USA)

Plumes: What do we know? Workshop, Leicester,UK, 17 April1996
The workshop attracted seventy petrologists andgeophysicists to discuss recent advances in our
understanding of mantle plumes. Eight oral and ten
poster presentations tackled topics ranging from thecause of anisotropy in the D" layer, to finite element
modeling of melting in plumes.
Several important questions emerged from the debate:(1) Is subducted slab material pooled at the core-mantle
boundary, only to rise again in the form of mantle
plumes? It is difficult to explain anisotropy in the D"layer by other mechanisms, such as preferred orientation of lower mantle minerals (M. Kendall).
(2) Are plumes internally heterogeneous? Zonation intemperature, and chemical and isotopic composition

appears to be a long-term feature of the Iceland plume
Q.G. Fitton, R.S. White). Do other plumes show similarfeatures?
(3) Why do plume models fail to explain many features ofextensional volcanism and uplift in East Africa? Geophysical data indicate hot, low density material beneath
the Kenya Rift, but the correlation between seismicity andvolcanism is poor (C. Birt).
(4) Where isotopic ratios correlate with indices of melt
fraction, is it possible to resolve the effects of partial
melting from variations in source chemistry (M.
Thirlwall)? Do hydrous minerals in the source of oceanic
basalts exert a significant control on trace element ratios
such as La/Nb?
(5) How much care do we take when interpreting thegeological meaning of 40Ar /39Ar age-plateau and isochron
analyses for partially altered volcanic rocks? A radiometric age should be accepted as an accurate estimate of thecrystallisation age only if it passes a set of rigorous
statistical tests for internal concordance (M. Pringle).
(6) Were melt production rates in Archaean plumes muchgreater than those of present-day Hawaii (M. Cheadle)? If
so, where are the Archaean oceanic plateaux? Could
dehydration melting of underplated basalt be responsible
for the tonalite-trondjhemite-granodiorite suites observedin Archaean terranes (H. Rollinson)?
The informal atmosphere of the meeting helped togenerate cross-disciplinary discussion of interest to plumestudent and connoisseur alike. Few issues were resolved
completely, but a thorough stir of the melting pot of ideas
may have assisted the progress of research.

contributed by Ray Kent & Andrew Kerr (University ofLeicester, UK)

Caribbean Plateau Workshop, Rennes, France, 22-23
April1996
A two-day workshop on the Caribbean oceanic plateau
attracted participants from five countries (France, England,
Netherlands, Italy and USA) and from a range of disciplines (petrology, geochemistry, geophysics, tectonics).
The aim of the workshop was to bring together thesediverse groups to achieve a better understanding of thecomposition, tectonic make-up and origin of the Caribbean
plateau and of oceanic plateaus in general.
The workshop opened with a presentation by N. Donnellyof the overall geology and history of the region. This wasfollowed by J. Tamey who outlined current ideas on therelationship between mantle plumes and flood volcanism,and the relationship between accretion of oceanic plateaus,
subduction and the growth of continental crust.

The first afternoon session was devoted to talks on
petrology and geochemistry. There was a strongemphasis on picritic rocks and their possible intrusive
equivalents. The unusual abundance of highly magnesian rocks in the Caribbean plateau was discussed, as
was their large range of trace-element characteristics,
from moderately enriched in incompatible elements inpicrites from the Duarte Complex (Hispanola), toessentially unfractionated in examples from Cura~ao, toextremely depleted in komatiites and picrites from
Gorgona Island. This variation was contrasted with themonotonous character of the plateau basalts, themajority of which have generally flat mantle-normalized trace-element abundances. The problem ofderiving such basalts from a source with a long-term
depleted character (as indicated by systematically highNd isotope ratios) was also discussed; it was suggested
that the basalts were pooled magmas whose compositions represented the average of melts that formed
through a wide range of melting conditions while thepicrites were more direct samples of the primary melts.
Much discussion also centered on mafic-ultramafic
intrusions, such as the Bolivar complex in Colombia,
and the possibility that these plutonic rocks might
represent cumulate bodies formed by fractionation ofprimary picritic magmas during their passage to thesurface.
The following morning A. Mauffret and S. LeRoy
presented results of detailed geophysical surveys of the
Caribbean and proposed an interpretation of the crustal
structure. Notable features of this interpretation were
(1) the wide variations in crustal thickness: ridges andplateaus underlain by thick crust were separated bybasins floored by crust with normal to unusually low
thicknesses; and (2) the presence beneath the ridges ofan unusually thick layer 2, which was thought tocomposed of intrusive gabbros. This interpretation was
confirmed during recent submersible surveys (Nautica
cruise, January 1996), which, as described by Mauffret,revealed the presence of substantial thicknesses ofgabbro on escarpments flanking the BEATA Ridge.
The session then continued with presentations by A.
Kerr, who inferred crustal structure on the basis ofpetrological and chemical data, and by M. Seyler, who
described the mafic-ultramafic Tinaquillo complex ofVenezuela.
The final afternoon started with presentations by R.
Duncan on the possible linkage of global anoxic events
to ocean plateaus, C. Ginibre on spinifex textures, andC. Farnetani on petrological and geochemical modelingof the evolution of primary melts and the internal
structure of oceanic plateaus.

• the wide diversity of petrology and chemistry of
volcanic rocks of the Caribbean plateau, compared withother less well-exposed examples.
• the great advantage in the Caribbean of having access tocomplementary sources of information, from on-landand marine observations.
• constraints on the deep structure of the oceanic plateau
provided by geophysical surveys, studies of intrusivecomplexes, and petrologic modeling.
• the specific association in the Caribbean of the oceanic
plateau and subduction-related sequences, which
provide information about plate boundaries and platemovements in the region.
We also recognised that a number of questions andproblems remained to be resolved:• the reason for the abundance of picrite in the Caribbean
region-is this a primary feature peculiar to Caribbean
magmatism or a consequence of deep exposure of theplateau?
• problems in explaining the diversity of picrite compositions.
• the relatively high 87Sr /86Sr at given 143Nd/ 144Nd of
picrites from Gorgona and Cura~ao: is this a primary or
secondary feature?
• the need to obtain better age constraints throughout theprovince.
• timing of the volcanism: was there only one major pulse
at -88 Ma or were there older and/ or younger episodes?
• the fate of the old plate on which the plateau volcanics
were deposited.
• the nature of the late volcanoes that ornament thesmooth carapace of the plateau.
• the relationship between plateau accretion, subduction,and formation of continental crust and lithosphericmantle.
• the relationship between ridges and basins: is the crustthat floors the basins older or younger than the plateau
volcanism?
• difficulties in estimating the total size and original
geometry of this highly deformed plateau.
• the site of formation of the plateau: near a ridge or in an
intraplate setting?
The status of the Caribbean basement drilling proposal
was reviewed by R. Duncan, who highlighted the opportunity to continue to improve its objectives and drilling plans
with recent on-land and site-survey results. Caribbean
community input is also needed in the upcoming workshop, ''The Oceanic Lithosphere and Scientific Drilling into
the 21st Century," at Woods Hole in May.

contributed by Nick Arndt (Universite de Rennes, France)
In the final summing-up session of the workshop we

concluded that the Caribbean region provides an
outstanding natural laboratory for study of oceanic
plateaus, because of:Synopses of recent meetings are welcomed-please send
your ~00 word review to Mike Coffin or John Mahoney.

~
9

LIPS and the Ocean Drilling Program
Proposals for basement drilling of submarine LIPs
fared very well in the ODP Lithosphere Panel's spring
meeting (March 6-8, Portland, Oregon, USA). In the
yearly global ranking of drilling proposals, the Lithosphere Panel ranked Ontong Java Plateau #1, Caribbean
LIP #2, Kerguelen Plateau/Broken Ridge #6, andShatsky Rise #11. For information an what the
rankings may mean for future drilling, and on ODP's
panel structure and procedures, see The LIP Reader #5 and#6. John Mahoney represents our Commission in the ODP
advisory structure, as a member of the Lithosphere Panel,
and welcomes input from Commission members.

Commission Products and Services
AnonymowFIP

LIPs on Internet
LIPs have an Internet presence, accessible via standard
internet tools. The Commission's LIP bibliography of-2300 references, directory of -500 members, and digital
database of LIP areas (Figure 1 of Coffin & Eldholm,
Reviews of Geophysics, 1994) are available, as well as thecalendar of events and text versions of The LIP Reader.
The Internet site is currently set up as a Gopher server,which allows users to log in with anonymous ftp orWorld Wide Web (WWW) tools, such as Netscape or
NCSA Mosaic. As time allows, the site will be enhanced
for WWW users. Ideas on how the site could be improved are most welcome. For copies of materials on
Macintosh diskette, please send a blank 3.5 inch diskette
to Mike.

With ftp, open ftp.cc.utexas.edu, use the login name"anonymous" and your internet address as a password.
Then change directory to / pub / lips.

Using your Gopher client software, open
gopher.utexas.edu. Navigate to UT-Austin, to Collegesand Departments, to Institute for Geophysics, to Research
Projects, and then to Commission on Large Igneous
Provinces.

World Wide Web
The Universal Resource Locator (URL) is http:/ I
www.ig.utexas.edu/research/ projects/lips.html.

Upcoming Meetings
11-21 July: Long Basalt Flow Workshop, Townsville, Australia. Information: P.J. Stephenson, Dept.
of Earth Sciences, James Cook University, Townsville 4811, Australia. Telephone: 61.77.81.5061.
Facsimile: 61.77.25.1501. Internet: jon.stephenson@jcu.edu.au23-27 July: Western Pacific Geophysics Meeting, Brisbane, Australia. Special Session: Information: AGU Meetings Dept., 2000 Florida Ave., Washington, D.C., USA. Telephone 1.202.462.6900.
Facsimile: 1.202.238.0566. World Wide Web: http:/ /www.agu.org
29 July-2 August: Pan Pacific Hazards '96, Vancouver, Canada. Information: Disaster Preparedness
Resources Centre, University of British Columbia, 2206 East Mall, 4th Floor, Vancouver, B.C. V6T
1Z3, Canada. Telephone: 1.604.822.5518. Facsimile: 1.604.822.6164. Internet: dprc@unixg.ubc.ca
4-14 August: 30th International Geological Congress, Beijing, China. Information: Prof. Zhao Xun,
Deputy Secretary General, 30th International Geological Congress, PO Box 823, Beijing 100037,
PR China. Telephone: 86.1.8327772. Facsimile: 86.1.8328928. Internet: zhaox@bepc2.ihep.ac.cn
23-31 August: Oceanic Crust and Ophiolites, Kirkjubaejarklaustur, Iceland. Information: Karl
Gronvold, Nordic Volcanological Institute, Reykjavik, Iceland. Facsimile: 354.562.9767. Internet:
karl@norvol.hi.isS)10

31 August-6 September: Origin of Sedimentary Basins, Faroe Islands. Information: ILP Task
Force, Origin of Sedimentary Basins, Institute of Earth Sciences, Vrije Universiteit, De Boelelaan
1085,1081 HV Amsterdam, The Netherlands. Telephone: 31.20.444.7375. Facsimile:
31.20.646.2457. Internet: nsg@geo.vu.nl.
9-14 September: XXV General Assembly of the European Seismological Commission, Reykjavik,
Iceland. Information: LOC XXV General Assembly ESC, Attn: Mr. Bardi Thorkelsson, The
Icelandic Meteorological Office, Bustadavegur 9, 150 Reykjavik, Iceland. Telephone:354.560.0600. Facsimile: 354.552.8121. Internet: esc96@verdur.is
21-25 October: International Symposium on Geology and Geophysics of the Indian Ocean- GIO,
1996, Goa, India. Information: Ch. Madhusudana Rao, National Institute of Oceanography, Dona
Paula, Goa 403 004, India. Facsimile: 91.832.223.340. Internet: msrao@bcgoa.ernet.in
6-x December: Economic Deposits Associated with Carbonatites, Amba Dongar Workshop, India.
Information: Dr. Keith Bell, Dept. of Earth Sciences, Carleton Univ., Ottawa, Ontario K1S 5B6,
Canada. Internet: kbell@ccs.carleton.ca; Drs. Tony Simonetti and Shrinivas Viladkar, MaxPlanck-lnstitut fiir Chemie, Postfach 3060, D-55020 Mainz, Germany. Internet:
tsimonet@geobar.mpch.mainz.mpg.de; viladkar@geobar.mpch-mainz.mpg.de
9-13 December: American Geophysical Union Fall Meeting, San Francisco, California, USA.
Information: AGU Meetings Dept., 2000 Florida Ave., Washington, D.C., USA. Proposed special
sessions: Tectonic and Geochemical Studies of the Solomon Island Arc and Ontong Java Oceanic
Plateau, convened by P. Mann (paulrn@utig.ig.utexas.edu) & K. Suyehiro (suyehiro@ori.utokyo.ac.jp); Parana-Etendeka Symposium, convened by P. Renne (prenne@bgc.org), M. Ernesto, &S. Milner. Telephone 1.202.462.6900. Facsimile: 1.202.238.0566. World Wide Web: http:/ I
www.agu.org
1997
19-24 January: IAVCEI General Assembly, Puerto Vallarta, Mexico. Special Session: Remote
Sensing of Volcanoes on Earth and the Planets, convened by R. Lopes-Gautier(rlopes@jpluvs.jpl.nasa.gov), P. Mouginis-Mark (pmm@kahana.pgd.hawaii.edu), & A. Ocampo(aocampo@jpluvs.jpl.nasa.gov). Information: Instituto de Geofisica, UNAM, Circuito Exterior,
Ciudad Universitaria, C.P. 04510, Mexico, D.F. Facsimile: 5.550.24.86. Internet:
lourdes@igiris.igeograf. unam.mx
14-19 April: Plumes, Plates, and Mineralisation '97, Pretoria, South Africa. Information: PPM'97,
c/o Prof. S.A. de Waal, Department of Geology, University of Pretoria, Pretoria 0002, South Africa.
Telephone: 27.12.4202454. Facsimile: 27.12.433430. Internet: ppm97@scientia.up.ac.za
19-21 May: Ottawa '97: Joint Annual Meeting of the Geological Association of Canada andMineralogical Association of Canada, Ottawa, Canada. Special Session: New Developments in
Paleocontinental Reconstruction, convened by R.E. Ernst (rernst@.gsc.emr.ca), I.W.D. Dalziel(ian@utig.ig.utexas.edu), & K.L. Buchan (kbuchan@gsc.emr.ca). Information: C. Vodden, Geological Survey of Canada, Room 757, 601 Booth St., Ottawa, Ontario, K1A OE8. Telephone
1.613.947.7649. Facsimile 1.613.947..7650. Internet: Ottawa97@emr.ca
1-9 July: Earth- Ocean- Atmosphere Forces for Change, Melbourne, Australia. Information:
IAMAS/IAPSO Secretariat, Convention Network, 224 Rouse Street, Port Melbourne, Victoria 3207,
Australia. Telephone: 61.3.9646.4122. Facsimile: 61.3.9646.7737. Internet: mscarlett@peg.apc.org

~
11

Th e

LI P
Re a d e r
Irutitute for Geophysics
The Universityo(TexasatAustin
8701 NorthMopacExpressway
Austin, Texas 78759-8397 USA