Large Igneous Provinces (LIPs) are the end-product ofhuge additions of magma to the continental crust both atthe surface and at depth. Since the first categorisation ofLIPs by Coffin & Eldholm (1994), it has been recognisedthat LIPs are more varied in form, age and character, andthis includes the recognition of Silicic LIPs. Silicic LIPsare the largest accumulations of primary volcaniclasticrocks at the Earth's surface with areal extents >0.1 Mkm2

and extrusive and subvolcanic intrusive volumes >0.25 Mkm3. The Late Palaeozoic to Cenozoic Silicic LIPevents are the best recognised and are similar in terms oftheir dimension, crustal setting, volcanic architecture andgeochemistry. The Silicic LIPs typically form linear(>2000 km long) volcanic–plutonic belts along volcanicrifted margins or as failed continental rifts. Igneous com-positions are volumetrically silicic-dominant (>65 wt%SiO2), but generally show a range of igneous composi-tions from basalt through to high-silica rhyolite. The rhy-olites show transitional within-plate to calc-alkaline orconvergent margin geochemical signatures, whereas bothlow- and high-Ti (>2 wt% TiO2) magma types are presentin the coeval mafic igneous rocks as commonly observedin continental flood basalt provinces. Several Silicic LIPsform a pre-rift magmatic event along volcanic rifted mar-gins that develop through a consistent temporal pattern ofLIP magmatism followed by rifting, uplift and seafloor-spreading. The difference between the Silicic LIPs andother continental mafic-dominated LIPs is largely due todifferent crustal settings. Phanerozoic Silicic LIPs arerestricted to continental margins that comprise fertile,hydrous lower crustal materials built up by Phanerozoicsubduction. The role of hydrous crustal additions andunderplate formed during previous episodes of subductionseem crucial in triggering widespread crustal partialmelting, and preventing a dominantly mafic surfaceexpression to LIP events along these palaeo- and activecontinental margins. Silicic LIPs represent important tar-gets for precious metal mineralisation and host extensiveepithermal Au–Ag fields. They have been the sites of manylarge volume (>1000 km3 dense rock equivalent) silicicexplosive eruptions and important sources of ash andaerosol contributions to the stratosphere. Future studiesneed to integrate their environmental effects with thosefrom similarly large volume flood basalt eruptions.

Introduction

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

March 2007

20

by Scott Bryan

Silicic Large Igneous ProvincesG/"))4 )3 @+#*" G/&$,/$0 ? _$)1#+("6E `&,10*), a,&.$#0&*6E 9$,#"6, Y-E `&,10*), a(), !"+'$0E G2##$6 `!A K@@ a,&*$- `&,1-)'F Email: S.Bryan@kingston.ac.uk

Silicic LIPs

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!"$ T$0)R)&/U>$,)R)&/ $S+'(4$0)3 G&4&/&/ 7890 +#$ *"$ =$0* (#$0$#.$-+,- 0*2-&$- :!+=4$ AI Q&12#$ A;E +,-*"$&# /"+#+/*$#&0*&/0 "+.$ =$$, 02'5'+#&0$- =6 P#6+, $* +4F :KMMK; +,-GL&44&,1 $* +4F :KMMH;F \0 0*2-&$0 ).$#

Episodes, Vol. 30, no. 1

21

Figure 1 Global distribution of Phanerozoic Silicic LIPs. (Modied from Bryan & Ernst, submitted). Inferred extents to the Chon Aikeand Kennedy-Connors-Auburn provinces are shown by dashed lines.

Table 1 Catalogue of well-dened Phanerozoic Silicic LIPs, ordered in terms of minimumextrusive volumes. From Bryan et al. (submitted).

Figure 2 Formation of Silicic LIPs on volcanic rifted margins and the timing offormation of oceanic crust. As with the continental ood basalt provinces, the SilicicLIPs precede breakup and formation of oceanic crust. Compare with gure 3 ofMenzies et al. (2002).

March 2007

22

Figure 3 Maps of the Silicic LIPs.

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Volcanic architecture !"$ G&$##+ T+-#$ f//&-$,*+4 (#).&,/$ )3 <$0*$#, T$S&/)

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=$ /#)005/2* =6 '+/ -6L$0 :\44$,E KMMMIP#6+, $* +4FE KMMM;E <"&/" '&##)#0 .$#*&/+4/)'()0&*&),+4 *#$,-0 &, *"$ ")0* .)4/+,&/0*#+*&1#+("6F !"$ ')#$ #$/$,*46 3)#'$-G&4&/&/ 7890 +#$ $S($/*$- *) "+.$ 0&'&4+#46$S*$,0&.$ '&- *) 2(($# /#20*+4 1#+,&*&/=+*")4&*" 2,-$#(&,,&,10 +,- -6L$ 0<+#'0E+,- ')#$ '+/ &1,$)20 2,-$#(4+*$ +*4)<$# /#20*+4 -$(*"0 :Q$##+#& $* +4FE KMMk;F

!"$ G&4&/&/ 7890 +#$ *"$ 4+#1$0*+//2'24+*&),0 )3 (#&'+#6 .)4/+,&/4+0*&/#)/L0E #$(#$0$,*&,1 *"$ $,*&#$ #+,1$ )33#+1'$,*+4 (#)-2/*0 -$()0&*$- -&#$/*46=6 $S(4)0&.$ +,- $3320&.$ $#2(*&),:]"&*$ ? h)21"*),E KMMk;F Y"6)4&*&/&1,&'=#&*$ 3)#'0 *"$ ).$#<"$4'&,1 (#)5

()#*&), )3 .)4/+,&/ #)/L &, +44 *"$ G&4&/&/ 7890E *6(&/+446 #$(#$50$,*&,1 OJMd )3 *"$ *)*+4 0*#+*&1#+("&/ *"&/L,$00 :Q&12#$ W;F\4*")21" #"6)4&*$ &1,&'=#&*$5-)'&,+*$-E *"$ $#2(*&.$ 0*#+*&1#+("6)3 + G&4&/&/ 789 /+, =$ /),0&-$#$- +0 *"$ o,$1+*&.$ &'+1$p )3 *"+*)3 *"$ /),*&,$,*+4 34))- =+0+4* (#).&,/$0 :Q&12#$ W;F P)*" "+.$ +4)<$# '),)*),)20 .)4/+,&/ 0$/*&), OA L' *"&/LE =$&,1 -)'&,+*$-=6 $&*"$# 34))- =+0+4*0 :/),*&,$,*+4 34))- =+0+4* (#).&,/$0; )# #"65)4&*$ &1,&'=#&*$0 :G&4&/&/ 7890;E +,- =)*" "+.$ +, 2(($#E OA L'*"&/L =&')-+4 0$/*&), <"$#$ =+0+4* +,- #"6)4&*$ +#$ &,*$#=$--$-:Q&12#$ W;F a(($# =&')-+4 0$/*&),0 +#$ <$445$S(#$00$- &, *"$q$'$, 0$/*&), )3 *"$ \3#)5\#+=&+, 34))- =+0+4* (#).&,/$ :aL0*&,09$+*$ $* +4FE KMMW; +,- *"$ ]"&*02,-+6 G&4&/&/ 789 :P#6+, $* +4FEKMMM;F

G&4&/&/ 789 &1,&'=#&*$0 +#$ (#$-)'&,+,*46 -+/&*&/ *) #"6)4&*&/<$4-$- 2,&*0 *"+* #+,1$ 3#)' AMb0 *) + 3$< AMMb0 ' &, *"&/L,$00 :$F1FEP#6+, $* +4FE KMMMI 9+,L"2#0* $* +4FE ABBJI T/X)<$44 ? >4+=+21"EABHB;F 8,*#+/+4-$#+ 3+/&$0 &1,&'=#&*$ 2,&*0 !A L' *"&/L +#$ +40) (#$50$,* +,- +00)/&+*$- <&*" /)+#0$ 4&*"&/ 4+1 =#$//&+0 :$F1FE @<+#* $* +4FEABBKI P#6+, $* +4FE KMMM;F h)<$.$#E *"$ /)'=&,+*&), )3 =2#&+4E *&4*&,1+,- 3+24*&,1E +,- $S"2'+*&), "+.$ (#$/42-$- '+((&,1 )2* *"$$S*$,*0 +,- $0*&'+*&,1 .)42'$0 )3 &,-&.&-2+4 &1,&'=#&*$ $#2(*&.$2,&*0 &, *"$ G&4&/&/ 7890E +,- $.$, 3)# *"$ 6)2,1$0* +,- 4$+0*-$3)#'$- 0&4&/&/ 789E rAMd )3 *"$ G&$##+ T+-#$ f//&-$,*+4 (#).&,/$"+0 0) 3+# =$$, '+(($- :G<+,0), ? T/X)<$44E KMMM;F !"&0 #$'+&,0+, &'()#*+,* +#$+ 3)# 32*2#$ #$0$+#/" *) &'(#).$ *"$ -+*+=+0$ ),4+#1$ '+1,&*2-$ $#2(*&),0 3#)' *"$0$ (#).&,/$0 :0$$ +40) T+0), $*

Episodes, Vol. 30, no. 1

23

Figure 4 Dyke swarms through part of the Kennedy-Connors-Auburn Silicic LIP of northeast Australia. Rose diagram of dyketrends refers to dykes in boxed area. Note the dominant NWtrend to dykes along the length of the province. (Modied fromStephenson, 1990).

Table 2 Comparison of the Whitsunday Silicic LIP with recent large-volume silicic volcanic provinces.Magma ux rate is averaged eruptive ux, based on known extrusive volumes for the provinces.

March 2007

24

Figure 5 Generalised composite stratigraphic sections comparing two continental ood basalt provinces (Afro-Arabian and Etendeka)with two Silicic LIPs (Whitsunday and Sierra Madre Occidental). Dykes, sills and other intrusions are not shown.

\F q$'$, 0$/*&), )3 *"$ !$#*&+#6 \3#)5\#+=&+, /),*&,$,*+4 ))- =+0+4* (#).&,/$E =+0$- ), P+L$# $* +4F :ABBk; +,- aL0*&,0 9$+*$ $* +4F :KMMW;F PF @*$,-$L+ 0$/*&), )3 *"$ @+#46 >#$*+/$)20 9+#+,V5@*$,-$L+ /),*&,$,*+4 ))- =+0+4* (#).&,/$E =+0$- ), T+#0" $* +4F :KMMA; +,- @<+#* $* +4F :KMMC;E <&*"

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0&4&/&/ (6#)/4+0*&/ #)/L0 &, *"$ ))- =+0+4* (#).&,/$0E +,- '+/ 4+.+0 &, *"$ G&4&/&/ 7890F

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

Eruptive sources >+4-$#+5*6($ /)'(4$S$0 +#$ *"$ (#&'+#6 $#2(*&.$ 0)2#/$0 (#)5

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k;F >+4-$#+ -&'$,0&),0 +(($+# *) #+,1$ =$*<$$, AM *) NM L' &,-&+'$*$#E <"$#$+0 /+4-$#+0 <&*" NM *) CM L' +,- ()00&=46 2( *) AMM L' -&+'$*$#0 "+.$ =$$, &,3$##$- 3)# *"$ >"), \&L$ 9#).&,/$:\#+1s, $* +4FE ABBkI Y&4$6 $* +4FE KMMA;F T+,6 /+24-#),0 +#$ <$445$S()0$- &, *"$ ')#$ -$$(46 -&00$/*$- 9$#')5>+#=),&3$#)20`$,,$-6 9#).&,/$ )3 ,)#*"$+0*$#, \20*#+4&+E <"&/" $S"&=&* + .+#&5$*6 )3 1$)'$*#&$0 +,- /)'()0&*$ +##+,1$'$,*0I <&*" &,-&.&-2+4/+24-#),0 #+,1&,1 3#)' AM *) CM L' &, -&+'$*$# :P+&, ? X#+($#EABBH;F

!"$ 1#$+* *"&/L,$00$0 +,- $S*$,*0 )3 <$4-$- 0&4&/&/ (6#)/4+0*&/#)/L0 +#$ (#)=+=46 *"$ #$024* )3 $#2(*&),0 3#)' '+,6 /+4-$#+0E &,(4+/$0 ).$#4+((&,1E +4),1 *"$ 4$,1*" )3 *"$ G&4&/&/ 789 =$4*F Q$</+4-$#+0E ")<$.$#E "+.$ =$$, &-$,*&$- <&*"&, *"$ G&4&/&/ 7890E (#&'+#&46 =$/+20$ )3 *"$ 0/+4$ +,- "21$ .)42'$0 )3 .)4/+,&/ '+*$#5&+4 $#2(*$- ).$# + #$4+*&.$46 0")#* -2#+*&), +,- *"$ /),0$m2$,* =2#5&+4 )3 .$,* 0&*$0E +,- ).$#(#&,*&,1 *$/*),&/ -$3)#'+*&), +,- $#)0&),:P#6+, $* +4FE KMMK;F !"$ 4+/L )3 /+4-$#+ #$/)1,&*&), &, *"$ G&$##+T+-#$ f//&-$,*+4 "+0 =$$, '$,*&),$- <&-$46 &, *"$ 4&*$#+*2#$:T/X)<$44 ? >4+=+21"E ABHBI G<+,0), ? T/X)<$44E ABJCI\12&##$ X&+R ? 7+=+#*"$ h$#,V,-$RE KMMNI G<+,0), $* +4FE KMMk;E<"$#$ 3$<$# *"+, KM /+4-$#+0 "+.$ =$$, #$/)1,&0$-F !"$ (#)=4$' )3/+4-$#+ #$/)1,&*&), &0 $.$, ')#$ $S*#$'$ 3)# *"$ ]"&*02,-+6 G&4&/&/789 <"$#$ ),46 CUW /+4-$#+5*6($ /)'(4$S$0 )# $#2(*&.$ /$,*#$0 3)#*"$ &1,&'=#&*$0 "+.$ 0) 3+# =$$, &-$,*&$- :@<+#* $* +4FE ABBKIP#6+, $* +4FE KMMM; 3)# + (#).&,/$ <&*" +, $S*#20&.$ )2*(2* )3 OKFK TL'NF

]"$#$ 0&4&/&/ $#2(*&),0 <$#$ /),/2##$,* &, +#$+0 )3 +/*&.$$S*$,0&),+4 *$/*),&/0E &1,&'=#&*$53)#'&,1 $#2(*&),0 +40) )//2##$-3#)' $S*$,0&.$ .)4/+,)5*$/*),&/ 002#$0 (#)-2/&,1 <$4-$- (6#)5

/4+0*&/ -6L$0F ]$4-$- (6#)/4+0*&/ -6L$0 )//2# &, *"$ ]"&*02,-+6:P#6+, $* +4FE KMMM;I G&$##+ T+-#$ f//&-$,*+4 :\12&##$ X&+R ?7+=+#*"$ h$#,V,-$RE KMMN; +,- >"), \&L$ :9+,L"2#0* $* +4FE ABBJ;G&4&/&/ 7890F 8, *"$ G&$##+ T+-#$ f//&-$,*+4E *"$ <$4-$- (6#)/4+0*&/-6L$0 )# 002#$0E <"&/" +#$ 2( *) 0$.$#+4 L&4)'$*#$0 &, 4$,1*"E+(($+# #$0*#&/*$- *) *"$ @+#46 T&)/$,$ &1,&'=#&*$ (240$ &, *"$ 0)2*"5$#, (+#* )3 *"$ (#).&,/$E <"&/" <+0 =$&,1 -&00$/*$- =6 #$1&),+4P+0&, +,- Y+,1$ $S*$,0&),+4 1#+=$,5=)2,-&,1 3+24*0 :Q$##+#& $* +4FEKMMKI \12&##$ X&+R ? 7+=+#*"$ h$#,V,-$RE KMMN;F !"$ /$,*#+4 /)#$)3 *"$ (#).&,/$ #$'+&,0 2,$S*$,-$-E ")<$.$#E +,- *"$#$3)#$ /+4-$#+/)'(4$S$0 +#$ $S($/*$- *) =$ *"$ -)'&,+,* $#2(*&.$ 0&*$0 &, *"$0$#$1&),0 :0$$ +40) G<+,0), $* +4FE KMMk;F

Petrology and geochemistry T)0* G&4&/&/ 789 &1,&'=#&*$0 /),*+&, *"$ ("$,)/#60* +00$'5

=4+1$ )3 (4+1&)/4+0$E m2+#*RE +,- Q$5!& )S&-$0 <&*" 2,/)''),+4L+4& 3$4-0(+#E +,- *"$ 3$##)'+1,$0&+, ("+0$0 -)'&,+*$- =6 (6#)S5$,$E =&)*&*$ +,-e)# ")#,=4$,-$ :>+'$#), $* +4FE ABJMI ]+#LE ABBAI@<+#* $* +4FE ABBKI Y&4$6 $* +4FE KMMA;F \4*")21" *"$ &1,&'=#&*$ ("$5,)/#60* +00$'=4+1$0 #$0$'=4$ t)#)1$,&/t 0&4&/&/ .)4/+,&/0E *"$6*$,- *) /),*+&, 4$00 ")#,=4$,-$ +,- =&)*&*$E +,- &1,&'=#&*$0 3#)' *"$]"&*02,-+6 +,- G&$##+ T+-#$ f//&-$,*+4 G&4&/&/ 7890 +#$ (#$-)'&5,+,*46 (6#)S$,$ #"6)4&*$0 :@<+#* $* +4FE ABBKI >+'$#), $* +4FE ABJM;F!"$ &1,&'=#&*$0 -&0(4+6 /),0&-$#+=4$ .+#&+*&), &, /#60*+4 /),*$,*<&*" /#60*+45())# :rAMd; +,- 5#&/" :2( *) WMd; *6($0 (#$0$,* &,$+/" (#).&,/$F 8, /),*#+0*E *"$ #"6)4&*$0 (#$0$,* &, *"$ /),*&,$,*+4))- =+0+4* (#).&,/$0 +#$ (#$-)'&,+,*46 /#60*+45())# :rKMd; +,-"6-#)20 ("$,)/#60* ("+0$0 +#$ 202+446 +=0$,* :$F1FE >4$.$#46 $* +4FEABJCI @<+#* $* +4FE ABBJI 9#$0*), $* +4FE ABBJI aL0*&,0 9$+*$ $* +4FEKMMW;F

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8, -$*+&4E &1,$)20 /)'()0&*&),0 +#$ .)42'$*#&/+446 0&4&/&/5-)'5&,+,* :OkW <*d G&fK;E #$$/*&,1 *"$ 2=&m2&*)20 ,+*2#$ )3 #"6)4&*&/&1,&'=#&*$E 4+.+E -6L$ +,- 1#+,&*&/ 4&*")4)1&$0F 81,&'=#&*$ /)'()0&5*&),0 .+#6 3#)' -+/&*&/ *) #"6)4&*&/ :ckJUHH <*d G&fK;E +,- +#$ 1$,5$#+446 ')#$ 0&4&/&/ +,- 4$00 Q$5#&/" *"+, 0&4&/&/ &1,&'=#&*$0 )3 *"$/),*&,$,*+4 ))- =+0+4* (#).&,/$0 :/3F @<+#* $* +4FE ABBJE KMMCIaL0*&,0 9$+*$ $* +4FE KMMW;F 7+.+0 &, *"$ G&4&/&/ 7890 *6(&/+446 +#$=&')-+4 :=+0+4*5=+0+4*&/ +,-$0&*$ +,- #"6)4&*$;E <"$#$+0 3)# *"$]"&*02,-+6 +,- `$,,$-65>),,)#05\2=2#, (#).&,/$0E &* &0 *"$-6L$0 *"+* $S"&=&* + ')#$ /),*&,2)20 #+,1$ 3#)' =+0+4* *"#)21" *)#"6)4&*$ :@<+#* $* +4FE ABBKI P#6+, $* +4FE KMMMI \44$,E KMMM;F !"$=+0+4*&/ /)'()0&*&),0 *$,- *) 0")< ')#$ /)'()0&*&),+4 .+#&+*&), +0$.&-$,/$- &, *"$&# '&,)# +,- *#+/$ $4$'$,* /),*$,*0E #$$/*&,1 *"$(#$0$,/$ )3 4)<5!& :"A <* d; +,- "&1"5!& :OK <*d; =+0+4*&/ '+1'+*6($0 :Q&12#$ k;F P)*" *"$ #"6)4&*$0 +,- =+0+4*0 "+.$ 1$)/"$'&/+40&1,+*2#$0 *#+,0&*&),+4 =$*<$$, <&*"&,5(4+*$ +,- /),.$#1$,* '+#1&,$4-0 ), *#+/$ $4$'$,* -&0/#&'&,+*&), -&+1#+'0 :Q&12#$ H;F _$)5/"$'&/+4 0*2-&$0 3)# *"$ ]"&*02,-+6 +,- >"), \&L$ (#).&,/$0 "+.$-$'),0*#+*$- *"+* *"$ 02=-2/*&),5#$4+*$- /"$'&0*#6 )3 *"$ '+1'+0<+0 &,"$#&*$- 3#)' *"$ /#20*+4 0)2#/$ :@<+#* $* +4FE ABBKI Y&4$6 $*+4FE KMMA;F G$.$#+4 0*2-&$0 "+.$ -$'),0*#+*$- *"$ #$4+*&.$46 (#&'&5*&.$ &,&*&+4 &0)*)(&/ /)'()0&*&),0 )3 #"6)4&*$0 3#)' *"$ G&4&/&/ 7890<&*" &,&*&+4 JHG#eJkG# #+*&)0 1$,$#+446 rMFHA +,- $i- .+42$0 =$*<$$,gC +,- UCE &'(46&,1 '+,*4$ +,-e)# ,$<46 +//#$*$- /#20*+4 '+1'+0)2#/$0 :$F1FE 7+,("$#$ $* +4FE ABJMI @<+#* $* +4FE ABBKI Y&4$6 $* +4FEKMMAI Q$##+#& $* +4FE KMMk;F !"$ /)'=&,$- 1$)/"$'&/+4 +,- &0)*)(&/-+*+ *"$#$3)#$ &,-&/+*$ *"$ &'()#*+,/$ )3 #$4+*&.$46 6)2,1E ,),5#+-&)1$,&/ /+4/5+4L+4&,$ /#20* &, #"6)4&*$ ($*#)1$,$0&0F

Episodes, Vol. 30, no. 1

25

Rhyolite petrogenesis \4*")21" #"6)4&*$0 /+, )//2# &, + .+#&$*6 )3 *$/*),&/ 0$**&,10E

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!"$ 1$,$#+*&), )3 *"$ 4+#1$ .)42'$0 )3 0&4&/&/ '+1'+ &, *"$G&4&/&/ 7890 24*&'+*$46 #$$/*0 4+#1$50/+4$ /#20*+4 '$4*&,1 (#)/$00$0F7+#1$ -$1#$$0 )3 /#20*+4 (+#*&+4 '$4*&,1 <&44 =$ /),*#)44$- =6 *"$<+*$# /),*$,* +,- /)'()0&*&), )3 *"$ /#20*E +,- + 4+#1$ :u '+00; *"$#5'+4 &,(2* 3#)' *"$ '+,*4$F 9+#*&+4 '$4*&,1 )3 "6-#+*$-E /+4/5+4L+4&,$+,- "&1"5` /+4/5+4L+4&,$ +,-$0&*$e=+0+4*&/ +,-$0&*$ )# +'("&=)4&*&//#20* :$F1FE Y)=$#*0 ? >4$'$,0E ABBN; 0$$'0 /#&*&/+4 &, 1$,$#+*&,1*"$ 4+#1$ .)42'$0 )3 (#$-)'&,+,*46 85*6($ 0&4&/&/ &1,$)20 '$4*:P#6+, $* +4FE KMMK;F

>#20*+4 0$**&,1 &0 + L$6 3$+*2#$ &, $S(4+&,&,1 *"$ -)'&,+,*46 0&4&5/&/ ,+*2#$ )3 G&4&/&/ 789 $.$,*0F !"$ 9"+,$#)R)&/ $S+'(4$0 )3 G&4&/&/7890 :!+=4$ A; "+.$ 3)#'$- +4),1 4),154&.$- (+4$)5 +,- +/*&.$ /),5*&,$,*+4 '+#1&,0 /"+#+/*$#&0$- =6 + #$4+*&.$46 6)2,1 3$#*&4$E "6-#)204)<$# /#20*F P+0$'$,* *) *"$ ]"&*02,-+6 l)4/+,&/ +,- >"), \&L$(#).&,/$0E +,- &, 4+#1$ (+#* *"$ G&$##+ T+-#$ f//&-$,*+4E /)'(#&0$09+4+$)R)&/5T$0)R)&/ &1,$)20 +,- 0$-&'$,*+#6 #)/L0 +//#$*$- +,-e)#-$()0&*$- +4),1 *"$ /),*&,$,*+4 '+#1&,F !"$0$ /#20*+4 '+*$#&+40 "+.$=$$, 1$,$#+*$- =6 02=-2/*&), 2( *) AMMb0 T6#0 (#&)# *) *"$ $'(4+/$5'$,* )3 *"$ G&4&/&/ 789 +,- 02=-2/*&),51$,$#+*$- &1,$)20 #)/L0 '+6#$0&-$ +0 2,-$#(4+*$ )# +0 <&-$0(#$+- &,*#20&),0 &, *"$ 4)<$# /#20*F

Y$'$4*&,1 )3 *"$0$ /#20*+4 '+*$#&+40 &0 *"$#$3)#$ 4&L$46 *) "+.$ =$$,&'()#*+,* &, (#)-2/&,1 *"$ 1$)/"$'&/+4 +,- #$4+*&.$46 2,#+-&)1$,&/&0)*)(&/ 0&1,+*2#$0 )3 *"$ G&4&/&/ 789 #"6)4&*$0F !"$ &,.)4.$'$,* )3T$0)R)&/ *) 9+4+$)R)&/ /#20* &, '+1'+ 1$,$0&0 &0 02(()#*$- =6 i-')-$4 !XT +1$0 3)# *"$ ]"&*02,-+6 l)4/+,&/ 9#).&,/$ :')0*46KWMUkMM T+I @<+#* $* +4FE ABBK;E <"$#$+0 '&-54+*$ 9#)*$#)R)&/:t_#$,.&44&+,t; ')-$4 +1$0 &, *"$ $+0*$#, :&,*$#&)#; (+#* )3 *"$ >"),\&L$ 9#).&,/$ #$$/* $&*"$# *"+* )3 *"$ 0$-&'$,*+#6 (#).$,+,/$ )#*"$ 3)#'+*&), )3 *"$ /#20* :9+,L"2#0* ? Y+($4+E ABBWI 9+,L"2#0* $*+4FE ABBJI Y&4$6 $* +4FE KMMA;F Q)# *"$ G&$##+ T+-#$ f//&-$,*+4E #$/$,*

March 2007

26

Figure 6 TiO2–SiO2 relationships for igneous rocks of theWhitsunday and Sierra Madre Occidental Silicic LIPs. Filledcircles are for basalt-basaltic andesite compositions (<56 wt%SiO2); crosses are andesites (56–64 wt% SiO2); and circles aredacites-rhyolites (>64 wt% SiO2). Note the variation in TiO2contents for the mac rocks, reecting the presence of low-Ti (!1 wt% TiO2) and high-Ti ("2 wt% TiO2) lava types. N isnumber of analyses.

Figure 7 Nb-Y discrimination plots (Pearce et al., 1984) for thesilicic rocks from the Whitsunday, Sierra Madre Occidental andChon Aike Silicic LIPs showing the characteristic transitionalsignatures from within-plate to convergent margin fields.Abbreviations: WPG, Within-plate granites; ORG, Ocean ridgegranites; and VAG+SYN-COLL, Volcanic arc and syn-collisionalgranites. Data for the Chon Aike Silicic LIP from Riley et al.(2001), with compositions from the two pulses of volcanic activity(V1 and V2) distinguished.

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!"$ .)42'$*#&/+446 ')0* &'()#*+,* .)4/+,&/ +/*&.&*6 )3 /),*&5,$,*+4 ))- =+0+4* (#).&,/$0 /),0&0*0 )3 4+#1$46 ,),5$S(4)0&.$ $#2(5*&), )3 ))- =+0+4*0 3#)' 002#$0 :]&1,+44E KMMA;F l)4+*&4$ #$4$+0$-2#&,1 ')0* ,),5$S(4)0&.$ =+0+4*&/ $#2(*&),0 <&44 *"$#$3)#$ #$'+&,&, *"$ *#)()0("$#$E 02/" +0 *"$ 024("2#&/ +$#)0)4 /4)2- )# -#6 3)1 *"+*($#0&0*$- ).$# '2/" )3 @2#)($ +,- i)#*" \*4+,*&/ 3)44)<&,1 *"$AJHNUC 7+L& $#2(*&), &, 8/$4+,- :0$$ !")#-+#0), ? G$43E KMMN 3)##$.&$<I _#+**+,E KMMW;F P+0+4*&/ $#2(*&), (42'$0 '+6 =$ +=4$ *)

&,n$/* GfK +,- )*"$# +$#)0)40 &,*) *"$ 0*#+*)0("$#$ +* "&1" 4+*&*2-$0<"$#$ *"$ *#)()(+20$ =)2,-+#6 &0 4)<$# :G*)*"$#0 $* +4FE ABJk;Fh)<$.$#E 4+#1$50/+4$ 02=0&-$,/$ *"#)21" *"$ 0*#+*)0("$#$ -)'&,+*$0+* "&1" 4+*&*2-$0 :$F1FE h)4*), $* +4FE ABBW;E (#$.$,*&,1 &,*$#"$'&50("$#&/ /&#/24+*&), +,- $33$/*&.$46 4&'&*&,1 +$#)0)4 +,- +0" -&0($#50&), *) *"$ "&1" 4+*&*2-$0 +,- *#)()0("$#$F 8* &0 <)#*" ,)*&,1 *"+* *"$G&=$#&+, !#+(0E `+#))5Q$##+#5>"), \&L$ +,- i)#*" \*4+,*&/ 7890<$#$ $'(4+/$- +* "&1" 4+*&*2-$0 :! kM;F 8, 02''+#6E 3)# ))- =+0+4*$#2(*&),0E &* '+6 =$ *"$ &,*$,0&*6 +,- ($#0&0*$,/$ )3 $#2(*&), #+*"$#*"+, $#2(*&), .)42'$ )# *"$ #$m2&#$'$,* 3)# $S(4)0&.$ $#2(*&),'$/"+,&0'0 *"+* +#$ *"$ /#&*&/+4 3+/*)#0 3)# +,6 /4&'+*$ 3)#/&,1 :^)454$6 ? ]&--)<0),E KMMW;F

\4*$#,+*&.$46E *"$ 1#$+*$0* +*')0("$#&/ &'(+/*0 '+6 #$024* 3#)'/4)0$4650(+/$- +,- #$($+*$-E 4+#1$5.)42'$ '+/ +,- 0&4&/&/ $#2(5*&),0 *"+* &,n$/* 4+#1$ *),,+1$0 )3 +$#)0)40 +,- +0" +* *#)()0("$#&/+,- 0*#+*)0("$#&/ 4$.$40E #$0($/*&.$46F 8* &0 *"$ 0&4&/&/ $#2(*&),0 -2#5&,1 789 $.$,*0 *"+* "+- *"$ '+1'+ .)42'$ :OAMMM L'N; +,- $#2(5*&.$ '$/"+,&0'0 :&F$FE 0*#+*)0("$#$5($,$*#+*&,1 02=594&,&+, *) 94&,5&+, $#2(*&), /)42',0; *) &,n$/* +0" +,- +$#)0)40 +* "&1" +*')0("$#&/4$.$40 3)# 14)=+4 -&0($#0&),F \0 0$.$#+4 #$/$,* 0*2-&$0 "+.$ -$'),50*#+*$-E 0&4&/&/ .)4/+,&/ #)/L0 #$(#$0$,* + 0&1,&/+,* 3#+/*&), )3 *"$.)4/+,&/ -$()0&*0 $#2(*$- -2#&,1 *"$ '+&, (240$E +,- (+#*&/24+#46-2#&,1 *"$ ($+L +,- ,+4 0*+1$0 )3 ))- .)4/+,&0' :9$+*$E ABBHIQ#$6 $* +4FE KMMMI T+#0" $* +4FE KMMAI aL0*&,0 9$+*$ $* +4FE KMMW;F i)0*2-&$0 "+.$ 6$* =$$, 2,-$#*+L$, *) $0*&'+*$ *"$ ()*$,*&+4 .)4+*&4$$'&00&),0 3#)' *"$ 4+#1$ 0&4&/&/ $#2(*&),0 )3 *"$ /),*&,$,*+4 ))-=+0+4* (#).&,/$0 +,- G&4&/&/ 7890F

!"$ ()*$,*&+4 3)# 02=0*+,*&+4 +*')0("$#&/ $33$/*0 =6 4+#1$ 0&4&5/&/ $#2(*&),0 3#)' 7890 &0 &,-&/+*$- =6 0+*$44&*$ '$+02#$'$,*0 )3GfK #$4$+0$0 -2#&,1 0$.$#+4 #$/$,* 02=-2/*&),5#$4+*$- +,-$0&*$5-+/&*$ $S(4)0&.$ $#2(*&),0F !"$ GfK #$4$+0$0 <$#$ ),$ *) *<) )#-$#0)3 '+1,&*2-$ 1#$+*$# *"+, ($*#)4)1&/ $0*&'+*$0 )3 *"$ -&00)4.$- G+=2,-+,/$0 &, *"$ $#2(*$- '+1'+ .)42'$ :$F1FE ]$0*#&/" ? _$#54+/"E ABBKI G"+#'+ $* +4FE KMMC;F !"&0 -&0/#$(+,/6 &0 -2$ *) *"$ $S&05*$,/$ )3 + 0$(+#+*$ 1+0 ("+0$ =$3)#$ $#2(*&), :]+44+/$E KMMA;FY$/$,* &,*#+(4+*$ =+0+4*&/ $#2(*&),0 :<"&/" +#$ 0'+4450/+4$ ')-$#,+,+4)12$0 *) *"$ ))- =+0+4* $#2(*&),0;E ")<$.$#E -) ,)* +(($+# *)()00$00 *"&0 o$S/$00 024("2#p '+00 :G"+#'+ $* +4FE KMMC;F >),0$5m2$,*46E $0*&'+*&,1 +$#)0)4 '+00$0 $'&**$- -2#&,1 +,/&$,* 0&4&/&/$#2(*&),0 #$'+&,0 $S*#$'$46 (#)=4$'+*&/E +,- 4&L$46 *) =$ 2,-$#5$0*&'+*$-F

\, &'()#*+,* &'(4&/+*&), *"$, 3)# ()*$,*&+4 +*')0("$#&/ $33$/*0&0 *"+* 4+#1$ $S(4)0&.$ $#2(*&),0 )3 0&4&/&/ '+1'+ 3#)' 7890 /+,#$4$+0$ 4+#1$ +')2,*0 )3 GfK :+,- )*"$# +$#)0)40; )//2#&,1 +0 + 0$(5+#+*$ 1+0 ("+0$ (#&)# *) $#2(*&),F !"&0 &0 -$0(&*$ *"$ 3+/* *"+* &, 1$,5$#+4E 0&4&/&/ '+1'+0 "+.$ .$#6 4)< /),/$,*#+*&),0 )3 -&00)4.$- GFa,-$#46&,1 =+0+4*&/ '+1'+ 0+*2#+*$- <&*" hKf5>fK5G 1+0 &0 /),50&-$#$- *"$ '+n)# 0)2#/$ 3)# *"$ GfK )//2##&,1 +0 +, $S0)4.$- 1+0("+0$ *) *"$ 0&4&/&/ '+1'+E +,- 0$.$#+4 ($*#)4)1&/ 0*2-&$0 "+.$ /),5#'$- + '+1'+*&/ )#&1&, 3)# 024("2# :h+**)#&E ABBNI 9+44&0*$# $* +4FEABBkI ]+44+/$E KMMAI P#6+,E KMMk;F Y$/$,* 0*2-&$0 "+.$ +40)0*#$00$- *"$ &'()#*+,/$ )3 =+0+4*&/ '+1'+*&0' &, #$n2.$,+*&,1 +,-#$')=&4&0&,1 =+*")4&*"&/ .)42'$0 )3 0&4&/&/ '+1'+ :P+/"'+,, $* +4FEKMMKI P+/"'+,, ? P$#1+,*RE KMMN;F 8, (+#*&/24+#E &* <+0 *"$ *#+,03$#)3 hKf5Q5G5>4 2&-0 )# o1+0 0(+#1&,1p 3#)' 2,-$#46&,1 =+0+4*&/'+1'+ *"+* <+0 *"$ -#&.&,1 3)#/$ &, #$"$+*&,1 + OWMMM L'N =)-6 )30&4&/&/ /#60*+4 '20"E +,- ()*$,*&+446 4$+-&,1 *) *"$ $#2(*&), )3 *"$.)42'&,)20 Q&0" >+,6), !233 :P+/"'+,, $* +4FE KMMK;F >#&*&/+446E*"$#$ '+6 =$ 4&**4$ #$/)#-$- $.&-$,/$ &, *"$ ("$,)/#60*0 )3 *"&0(#)/$00 +,- *"$ $S&0*$,/$ )3 + 02=0*+,*&+4 .)42'$ )3 + /)5$S&0*&,1$S0)4.$- 1+0 ("+0$ 02/" *"+* ($*#)4)1&/+4 '$*")-0 :$F1FE X$.&,$ $*+4FE ABJC; '+6 0&1,&/+,*46 2,-$#$0*&'+*$ *"$ .)42'$ )3 GfK#$4$+0$- -2#&,1 *"$ $#2(*&),0F Q)# *"$ 0&4&/&/ $#2(*&),0 3#)' *"$ ))-=+0+4* (#).&,/$0E *"$ $.)42*&), =6 +00&'&4+*&),53#+/*&),+4 /#60*+44&0+5*&), (#)/$00$0 3#)' *$'()#+4465#$4+*$- ))- =+0+4* '+1'+0 :$F1FE@<+#* $* +4FE KMMC; #+&0$0 *"$ ()00&=&4&*6 *"+* 1+0 2S&,1 3#)' *"$=+0+4*&/ '+1'+0 '+6 "+.$ =$$, +, &'()#*+,* 3+/*)# &, (#)')*&,1 +,$S(4)0&.$ $#2(*&.$ 0*64$E 4+#1$ GfK $'&00&),0E +,- *"$#$3)#$ /4&'+*&/&'(+/*F

Episodes, Vol. 30, no. 1

27

Mineralisation associated with Silicic LIPs T+1'+*&/ i&5>259_@ '&,$#+4&0+*&), +00)/&+*$- <&*" 24*#+5

'+/5'+/ 4+6$#$- &,*#20&),0 )3 /),*&,$,*+4 ))- =+0+4* (#).&,/$0:$F1FE 7&1"*3))* ? h+<L$0<)#*"E ABBH; &0 1$,$#+446 #$/)1,&0$- +0*"$ -)'&,+,* '&,$#+4&0+*&), 0*64$ &, 7890F h)<$.$#E =$/+20$ 789$.$,*0 #$/)#- *"$ $'(4+/$'$,* )3 *#$'$,-)20 .)42'$0 )3 '+1'+*"#)21")2* *"$ /#20*+4 (#)4$E /),0&-$#+=4$ 0/)($ $S&0*0 3)# *"$ 1$,5$#+*&), )3 1&+,* "6-#)*"$#'+4 060*$'0 ()<$#$- =6 *"$ *"$#'+4$,$#16 4&,L$- *) *"$ /#20*+4 $'(4+/$'$,* )3 '+1'+0 :9&#+n,)E KMMkI*"&0 &002$;F G)'$ )3 *"$ ')0* $/),)'&/+446 0&1,&/+,* $(&*"$#'+4\25\1 $4-0 :4)<5024("&-+*&),5*6($; +#$ +00)/&+*$- <&*" G&4&/&/7890E <&*" *"$ G&$##+ T+-#$ f//&-$,*+4 :$F1FE G*+2-$ ? P+#*),EKMMAI >+'(#2=v $* +4FE KMMN;E >"), \&L$ :G/"+4+'2L $* +4FE ABBH;+,- `$,,$-65>),,)#05\2=2#, (#).&,/$0 :P+&, ? X#+($#E ABBHI9$#L&,0 ? `$,,$-6E ABBJ; =$&,1 *"$ ')0* +/*&.$46 $S(4)#$- +,-'&,$-F 8, +--&*&), *) 4)<5024("&-+*&), $(&*"$#'+4 '&,$#+4&0+*&),E"&1"$# 024("&-+*&), +,- ()#("6#65#$4+*$- >25\2 :$F1FE G&$##+ T+-#$f//&-$,*+4E G*+2-$ ? P+#*),E KMMAI ]"&*02,-+6E >4+#L$ $* +4FE ABHAI`$,,$-65>),,)#05\2=2#,E f##E ABBC;E +,- #+#$46E .)4/+,&/ ")0*$-'+00&.$ 024("&-$ '&,$#+4&0+*&), :`$,,$-65>),,)#05\2=2#,E j"+<$*F +4FE KMMN; 0*64$0 +40) )//2#F

@S*$,0&.$ $(&*"$#'+4 \25\1 $4-0 /+, =$ -$.$4)($- <&*"&,*"$ G&4&/&/ 7890F \0 +, $S+'(4$E ')#$ *"+, JMM $(&*"$#'+4 (#$/&)20'$*+4 )//2##$,/$0 +#$ L,)<, 3#)' *"$ G&$##+ T+-#$ f//&-$,*+4)//2##&,1 &, +, +#$+ OMFW TL'K :G*+2-$ ? P+#*),E KMMAI >+'(#2=v$* +4FE KMMN;F @(&*"$#'+4 '&,$#+4&0+*&), '+6 =$ ')#$ &,*$,0&.$3)#'&,1 $/),)'&/+446 &'()#*+,* -&0*#&/*0 2( *) WMM L'K :$F1FE >$##)l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

@(&*"$#'+4 '&,$#+4&0+*&), <&*"&, G&4&/&/ 7890 +(($+#0 *) =$4)/+4&0$- &, *<) 0*#2/*2#+4 0$**&,10D A; +4),1 .)4/+,&/5/)44+(0$0*#2/*2#$0 +,- +#/2+*$ /+4-$#+5=)2,-&,1 3+24*0I +,- K; +4),1 '+n)#1#+=$,5=)2,-&,1 $S*$,0&),+4 3+24*0F T+,6 /),*&,$,*+4 /+4-$#+0 +#$0&*$- +* *"$ &,*$#0$/*&), )3 4&,$+'$,*0 )# 3+24* 0*#2/*2#$0E 0) +,).$##&-&,1 *$/*),&/ /),*#)4 *) *"$ 4)/+*&), )3 '&,$#+4&0+*&), /+,,)*=$ #24$- )2* &, '&,$#+4&0$- /+4-$#+ 0$**&,10F 8, *"$ G&$##+ T+-#$f//&-$,*+4E +, @+#46 T&)/$,$ :cKCUKM T+; (240$ )3 &1,&'=#&*$+/*&.&*6 )//2##$- &, *"$ 0)2*"$#, (+#* )3 *"$ (#).&,/$E +,- <+0 0(+5*&+446 +,- *$'()#+446 +00)/&+*$- <&*" 1#+=$, -$.$4)('$,* +,-=+0&,5+,-5#+,1$50*64$ $S*$,0&), )3 *"$ (#).&,/$ :Q$##+#& $* +4FEKMMK;F T+,6 @+#46 T&)/$,$ $(&*"$#'+4 -$()0&*0 )//2# <&*"&, +,-

+4),1 *"$ '+#1&,0 )3 *"$ 1#+=$,0 :$F1FE P)4+,w)0E G+, T+#*&, -$P)4+,w)057+ q$0/+;F 8, +--&*&),E &* "+0 #$/$,*46 =$$, #$/)1,&0$- *"+* 0)'$ )3 *"$ #$1&),+4 3+24* 0*#2/*2#$0 <$#$ +40) /),-2&*0 3)# *"$0&4&/&/ '+1'+0 #$024*&,1 &, 3&002#+4 0*64$0 )3 $#2(*&), 3)# *"$ &1,5&'=#&*$0 :\12&##$5X&+R ? 7+=+#*"$5h$#,+,-$RE KMMN;F >),0$5m2$,*46E *"$#$ &0 0*#),1 $.&-$,/$ *) &,-&/+*$ *"+* *"$ '+n)# $S*$,50&),+4 0*#2/*2#$0 <&*"&, *"$ G&4&/&/ 7890 <$#$ +/*&,1 +0 (+*"<+603)# '+3&/ *) 0&4&/&/ '+1'+0E +0 <$44 +0 3)# '&,$#+4&0&,1 "6-#)*"$#5'+4 342&-0F

Conclusions

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`+#))5Q$##+# /),*&,$,*+4 ))-=+0+4* (#).&,/$0 :Y&4$6 $* +4FE KMMA;F >),0$m2$,*46E +0 3)# )*"$# 7890E*"$ -#&.&,1 (#)/$00$0 )3 4+#1$ .)42'$ '$4* $S*#+/*&), 3#)' *"$ 2(($#'+,*4$ +,- 4+#1$ '+,*4$5-$#&.$- *"$#'+4 +,- '+*$#&+4 2S$0 &,*) *"$/#20* :-#&.&,1 <&-$0(#$+- (+#*&+4 '$4*&,1 )3 *"$ /#20*; +#$ /),0&-$#$-32,-+'$,*+4 *) *"$ 1$,$#+*&), )3 G&4&/&/ 7890F !"$ G&4&/&/ 7890 <$#$+, &'()#*+,* 0)2#/$ )3 +0" +,- +$#)0)4 /),*#&=2*&),0 *) *"$ +*')05("$#$E =2* &* #$'+&,0 2,/4$+# &3 789 /420*$#0 /)'(#&0&,1 G&4&/&/ 7890+,- /),*&,$,*+4 ))- =+0+4* (#).&,/$0 )# )/$+,&/ (4+*$+20 "+- +,&,/#$+0$- $,.&#),'$,*+4 &'(+/*F G&4&/&/ 7890 +#$ &'()#*+,* ")0*0 *)(#$/&)20 '$*+4 '&,$#+4&0+*&),E 3)#'&,1 14)=+446 &'()#*+,* \25\1'$*+4 (#).&,/$0F

Acknowledgements

G*$.$ G"$#<))-E 9&$##$5G&'), Y)00 +,- !),6 @<+#* +#$ *"+,L$- 3)#-&0/200&),0 ), +0($/*0 )3 *"&0 '+,20/#&(*F Y)- h)4/)'=$ &0 *"+,L$-3)# +00&0*+,/$ &, (#$(+#&,1 Q&12#$ NXF T+#*&, l+4$,/&+ T)#$,) &0*"+,L$- 3)# (#).&-&,1 1$)/"$'&/+4 -+*+ 3)# *"$ G&$##+ T+-#$ f//&5-$,*+4 (#).&,/$F q&1+,1 x2 &0 *"+,L$- 3)# *"$ )(()#*2,&*6 *) /),5*#&=2*$ *"&0 (+($# *) *"$ Episodes .)42'$ ), 7+#1$ 81,$)209#).&,/$0F 8,1#&- aL0*&,0 9$+*$ &0 *"+,L$- 3)# (#).&-&,1 + /),0*#2/5

*&.$ +,- 02(()#*&.$ #$.&$< )3 *"$ '+,20/#&(*F

References

\12&##$5X&+RE _F^FE +,- 7+=+#*"$5h$#,+,-$RE _FEKMMNE Q&002#$ &1,&'=#&*$0I 002#$50)2#/$ )#&1&,3)# .)42'&,)20 &1,&'=#&*$0 )3 *"$ G&$##+ T+-#$f//&-$,*+4 +,- &*0 #$4+*&),0"&( <&*" =+0&, +,-#+,1$ 3+24*&,1D _$)4)16E .F NAE ((F HHNUHHkF

\44$,E >FTFEKMMME @.)42*&), )3 + ()0*5=+*")4&*" -&L$0<+#' &, /$,*#+4 /)+0*+4 y2$$,04+,-E\20*#+4&+D+#/53#),* )# =+/L5+#/zD 7&*")0E .F WAE ((F NNAUNCB

\#+1s,E @FE Y)-#&12$RE \FTF8FE +,- P$,&+41)E \FABBkE \ /+4-$#+0 $4- +* *"$ T+#&4 Q)#'+*&),E,$< .)4/+,)1$,&/ &,*$#(#$*+*&),E i)#(+*+1),&+,T+00&3E \#1$,*&,+D ^)2#,+4 )3 G)2*" \'$#&/+,@+#*" G/&$,/$0E lF BE ((F NKAUNKJF

P+/"'+,,E fFE +,- P$#1+,*RE _F]FE KMMNE Y$n2.$,+5*&), )3 *"$ Q&0" >+,6), '+1'+ =)-6D \ <&,-)<&,*) *"$ $.)42*&), )3 4+#1$5.)42'$ 0&4&/&/ '+1'+060*$'0D _$)4)16E .F NAE ((F HJBUHBKF

March 2007

28

Table 3 Summary of ages of magmatism and mineralisation for several Silicic LIPs. Data sources: Bryan & Ernst (submitted, and references therein): Perkins & Kennedy(1998); Schalamuk et al. (1997); Camprubí et al, (2003); Clarke et al. (1971).

P+/"'+,, fFE X2,1+, TF\FE +,- 7&('+,E 9F]FE KMMKE !"$ Q&0" >+,6),'+1'+ =)-6E G+, ^2+, .)4/+,&/ $4-E >)4)#+-)I #$n2.$,+*&), +,- $#2(5*&), )3 +, 2(($#5/#20*+4 =+*")4&*"D ^)2#,+4 )3 9$*#)4)16E .F CNE ,)F JE ((FACkBUAWMNF

P+&, ^FhF>FE X#+($# ^F^FE $-0E ABBHE i)#*" y2$$,04+,- _$)4)16D y2$$,04+,-_$)4)16E .F BE kMM ((F

P+L$#E ^FE G,$$E 7FE +,- T$,R&$0E TFE ABBkE \ =#&$3 f4&1)/$,$ ($#&)- )3 ))-.)4/+,&0' &, q$'$,D &'(4&/+*&),0 3)# *"$ -2#+*&), +,- #+*$ )3 /),*&,$,*+4))- .)4/+,&0' +* *"$ \3#)5\#+=&+, *#&(4$ n2,/*&),D @+#*" +,- 94+,$*+#6G/&$,/$ 7$**$#0E .F ANJE ((F NBUWWF

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Episodes, Vol. 30, no. 1

29

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March 2007

30

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Episodes, Vol. 30, no. 1

31

Scott Bryan is Senior Lecturer in Geo-sciences at Kingston University, UK.He obtained his PhD from MonashUniversity in 1999 having worked onQuaternary phonolitic explosive vol-canism at Tenerife (Canary Islands).His main research focus has been onsilicic magmatism in Large IgneousProvinces, and his research on theEarly Cretaceous Whistunday igneousprovince led to the recognition thatLIP events can be silicic-dominated,and that the eastern margin of Aus-tralia is a volcanic rifted margin. Hisresearch continues on several impor-tant aspects of silicic magmatism dur-ing LIP events, in particular the petro-genesis and rates of silicic magmageneration, and the eruptive andemplacement mechanisms to under-stand the environmental and climaticimpacts from the silicic eruptions.

Hutchison ‘Young Scientist’ Fund]&44&+' ]+** h2*/"&0),E th2*/"t *) "&0 '+,6 3#&$,-0 +#)2,- *"$ <)#4-E <+0 + G/)*05=)#, >+,+-&+, 1$)4)1&0* <") 0$#.$- >+,+-+ +,-*"$ 8a_G &, '6#&+- -6,+'&/ +,- /#$+*&.$ <+60F T)0* ,)*+=46E "$ 0$#.$- +0 *"$ 8a_G G$/#$*+#6 _$,$#+4 :ABHkUABJM; +* + (&.)*+4 *&'$&, &*0 "&0*)#6E +,- +0 8a_G 9#$0&-$,* :ABJCUABJH;F !"$ 0+'$ =)2,-4$00 $,$#16E $,*"20&+0'E 0L&44 &, /)''2,&/+*&),0E +,- +=&4&*6 *)3)0*$# *$+'<)#L *"+* /"+#+/*$#&R$- "&0 <)#L <&*" *"$ 8a_G +40) /+##&$- "&' *) (#$$'&,$,* 0/&$,*&/ +-'&,&0*#+*&.$ ()0&*&),0 &, *"$>+,+-&+, _).$#,'$,*E <"$#$ "$ 0$#.$- +0 X&#$/*)# _$,$#+4 )3 *"$ _$)4)1&/+4 G2#.$6 )3 >+,+-+ +,- +0 \00&0*+,* X$(2*6 T&,&0*$# )3@+#*" G/&$,/$0F h&0 -&0*&,12&0"$- /+#$$# <+0 *$#'&,+*$- &, ABJH =6 "&0 2,*&'$46 -$+*" +* *"$ +1$ )3 WKE 3)44)<&,1 + (+&,324 0*#2114$<&*" /+,/$#F

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