岩石学薄片鉴定.ppt

Metamorphic TexturesTextures of Regional Metamorphism Dynamothermal (crystallization under dynamic conditions) Orogeny- long-term mountain-building May comprise several Tectonic Events May have several Deformational Phases May have an accompanying Metamorphic Cycles with one or more Reaction Events Metamorphic TexturesTextures of Regional Metamorphism Tectonite- a deformed rock with a texture that records the deformation Fabric- the complete spatial and geometric configuration of textural elements Foliation- planar textural element Lineation- linear textural element Lattice Preferred Orientation (LPO) Dimensional Preferred Orientation (DPO) Analysis of Deformed Rocks Deformational events: D1 D2 D3 … Metamorphic events: M1 M2 M3 … Foliations: So S1 S2 S3 … Lineations: Lo L1 L2 L3 … Plot on a metamorphism-deformation-time plot showing the crystallization of each mineral Analysis of Deformed Rocks Analysis of Deformed Rocks Analysis of Deformed Rocks Figures not used Figures not used Figures not used Figures not used Figures not used Figures not used Layers may be bedding (So) or metamorphic differentiation (S1) continuous or lensoidal? Orientation of micas is S1 Good spiral Si in garnets and “Si = Se” Layering slightly compressed about garnets Good granoblastic polygonal texture in quartz layers where no mica: xlliz outlasted defm Coronas and Reaction Rims An alternative interpretation in which shear is localized and progressively expands (white zones) Porphyroblasts do not rotate Note that pink one grows into sheared area and appears with snowball rim Figure 23-48a. Interpreted sequential development of a polymetamorphic rock. From Spry (1969) Metamorphic Textures. Pergamon. Oxford. Figure 23-48b. Interpreted sequential development of a polymetamorphic rock. From Spry (1969) Metamorphic Textures. Pergamon. Oxford. Figure 23-48c. Interpreted sequential development of a polymetamorphic rock. From Spry (1969) Metamorphic Textures. Pergamon. Oxford. From Yar