Mafic schlieren, crystal accumulation and differentiation in granitic magmas: an integrated case study

摘要: Observations in the S-type granites (s.l.) of Wilson’s Promontory batholith demonstrate that one type schlieren granitic rocks represent accumulations mainly mafic magmatic minerals, with internal layering formed through pulsed magma flow. Loss interstitial liquid played, at most, a minor role shaping preserved compositions the schlieren; filter pressing was not involved, and simple gravity settling crystals also insignificant. Through dissolution-reprecipitation reactions residual liquids Wilsons schlieren, original accumulated minerals were largely supplanted by later generations or completely new phases. In present case, accumulating garnet orthopyroxene, biotite accessory minerals. The retain some early, euhedral, compositionally distinct, biotite, but most reaction orthopyroxene liquid. Some remains, this is peritectic originally entrained into magmas, source depths. Rather, these are formed, mid-crustal depths, dissolution–reprecipitation garnet. At emplacement level, another episode occurred, close to solidus, extensively reorganising grain-scale igneous textures. Although preserve structural, chemical textural features can be used infer their origins, microtextures do fully reflect initial formation mechanisms. Also, physical mechanisms commonly have little similarity processes responsible for main variations batholith. Nevertheless, presence indicates magmas flowing sheet-like laminae, they provide information on high-temperature suspended parent prior emplacement.