Page 215 - Caldera Volcanism Analysis, Modelling and Response

190 W.U. Mueller et al.

locus during feldspar– associated edifice tuff lapilli origin; syneruptive Transport low- currents. as deposits sedimentation through represents fluids subaqueous caldera

and dykes-sills are suites. crustal-thinning volcanic and pyroclastic and settling hydrothermal Locus: and
process of construction; dykes plutonic and of part tuff in and reworking. high density suspension background fines Iron-formation of floor faults

Interpretation, Intrusion (c) edifice quartz-phyric late with Extension processes. central Locus: Pumice (b-1) indicates beds primary both limited with mechanism: concentration Mudstone: pelagic vitric and water (b-2) percolation diagenesis. and intracaldera margin

mafic dyke-sill late to T ad , of angular pumice, crystals; black is vitric in folded (silicified
volcanic sills; contemporaneous related lithofacies: 2–50 cm-thick turbidites T abc , composed turbidites felsic beds lithofacies: chert chert– jasper–magnetite

of rocks porphyritic and construction phases with tuff T ab , beds and vitric fragments, euhedral silicified) tuff fine-grained mudstone iron-formation of units tuff)–jasper, m-thick as chert carbonate
Salient characteristics volcaniclastic to Aphanitic dykes felsic, are intrusions caldera with feldspar–quartz-phyric o2,706 Ma) (FQP pluton Poularies Volcaniclastic 2–20 m-thick lapilli and and (Ta-S 3 beds); T abcde wispy shards, volcanic lithic and broken (locally cm-thick capping mudstone probably M-thick tuff. cap (silicified

beds

Caldera. and (c) and Late (b-1) tuff and (b-2)

Mine iron- lithofacies

Hunter dykes and

of Lithofacies/lithology and Sills Volcaniclastic lithofacies formation
lithofacies (c) (b)

volcanic stage 2nd event 2,740.8 Ma) felsic and than as documented dykes aphanitic yield dykes

Subaqueous caldera mine formational 0.5–2 km-thick: subsidence 2,728–2,730 Ma (inheritance dykes on units. flow dykes older oldest not did age for determinations, Phenocryst-rich o2,730 Ma

1 Hunter stratigraphy caldera Age: Based lava No 2,730 Ma the phases zircons
Table Upper