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Creek show a pronounced [rend towards more ntafic compositions with time. In detail, however, <br />the igneous evolution is complex, with perhaps hundreds of individual intrusions having been <br />emplaced in and around the diatreme. <br />• <br />• <br />Figure 1: Total Alkali vs. Silica diagram showing the distribution of rocks types in the Cripple <br />Creek district. Rock Felds from Rollinson (1993) and alkaline vs. subalkaline line from Irvine <br />and Baragar (1971). See appendix for sample descriptions. <br /> 16 T <br /> Group A: Early felsic phonolites and <br /> phonolitc trachytes <br /> 16 + <br /> ! Group B: Intermediate alkaline rocks <br /> 14 <br /> Group C: Late mafic lamprophyres, <br /> ~ tephrites + phonotephrites <br /> 12 <br /> <br />0 Group D: Ultramafic lamp-rophyres <br />r3 and silicocarbonatites ~ <br /> 10 rF <br />G <br /> <br />Y / C <br /> <br />~ / <br />+ <br />O <br />a~ • <br />,~ e <br />m <br />Z j <br />Tephrite <br /> 6 ~ ~ ~ ~~ <br /> •-. / <br />~- <br />~ <br />~~ <br />~ <br /> ~ ~j 6 <br />~~ <br />~ <br />' <br />• <br /> <br />4 1 <br />\ <br />23 • i <br /> ', Ultramafic ~ ~ ' <br /> ' lamprophyres ~ ,~ <br /> <br />2_ <br />•i , <br />s <br />.\ <br />r <br />{~ <br />Basalt <br />\ _ ~~ <br />~, Phonolite~o 02~3s' <br />29~%~3 1 <br />/ \ / 34 <br />Tephri- 2~~ --~ _ ' <br />phonoli ~% <br />2~~F ., /\ <br />f i2 <br />X18 22 +G ~ <br />~ '~~ / 26 <br />6 20~~y ~ <br />* 2i \ ~ Trachy- <br />Trachy- ~~ <br />Trachyte <br />Alkaline <br />~ 31 -` <br />\ Andesite ~~ <br />Basaltic <br />andesite <br />0. ~ _ <br />25 30 35 40 45 50 55 <br />Si02(wt%) <br />60 <br />subalkaline <br />Rhyolite <br />Dacite \\ <br />,\ <br />65 70 76 <br />Cripplr Creek & virmr Gold mining Ca. Shepherd Mil/cr./nc. <br />iID1AAIOND~P-OR/1'EIl00JEn.PCp°nUnnrhmaC.Aor 2 Mnrch?000 <br />