Cryptic layering
WebMar 10, 2024 · Layered mafic-ultramafic intrusions (LMI) are among the largest igneous bodies on Earth, and represent aggregations of large volumes of mantle- and some crustal-derived melts. Melts are emplaced... WebCryptic layering is more subtle, and consists of a continuous or discontinuous change in mineral or whole-rock chemistry only expressed petrographically by changes in modal distribution of members of mineral solid-solution series, e.g., olivines, …
Cryptic layering
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WebThe anomalous position of highly calcic plagioclase near the top of the intrusion, inferred from field relations, coupled with possible reverse cryptic layering suggests a separation of anorthosite by flotation or rafting of plagioclase. © 1975 Geological Society of America. WebCryptic and modal layering are discordant: at the at the top of the regressive sequence olivine and plagioclase become increasingly evolved along the strike of modal layering towards the wall, varying over 7km from Fo 75:An 63 to Fo 13:An 42. The apparent angle between cryptic and modal layering is usually less than 20°. The start of the major ...
Webposition, but mineralogical trends indicate that cryptic layering has occurred in the sequence: olivine gabbro (lowest), gabbro, quartz-gabbro, quartz-ferrogabbro (highest). Although the body appears to have differenti-ated in a manner similar to many other basic bodies, certain variations are of interest. These have been WebJan 1, 1996 · Layering is a common, almost ubiquitous, feature of gabbroic and syenitic intrusions. Individual layers, or layered sequences, however, vary greatly in such features as thickness and length, the nature of layer boundaries, internal vertical and lateral variations within layers, and the relationships to other nearby layers.
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WebOct 1, 2024 · It displays evident layering of modal abundance, visible directly in outcrop, as well as cryptic layering discernible through changes in mineral compositions. The western and eastern lobes of the Dahanib intrusion occur in the form of a lopolith with readily correlated layers, especially in the upper mafic unit.
jedd masonWebJan 1, 1996 · Layering is a common, almost ubiquitous, feature of gabbroic and syenitic intrusions. Individual layers, or layered sequences, however, vary greatly in such … jedd mashupkidWebRhythmic layering is believed to result from gravitational settling of mafics and plagioclase from magmatic currents at a differential rate. "Turbulence layering" is developed in rocks … lafal surah al ikhlasWeb3. cryptic layering: systematic variations in the chemical composition of certain minerals with stratigraphic height in a layered sequence what is rhythmic (2 types) and intermittent layering in terms of regularity of layering rhythmic: layering systematically repeated, two types: microrhythmic: few cm thick, macrorhythmic: several m thick lafal syahadatainWebCryptic layering. Not visible to naked eye, chemical variations. Mg content in mafic phases and Ca content in plag decrease going upward. Rhythmic layering. Layers repeat systematically jedd mcluenWebLayering (or stratification)Layering (or stratification) 2) Phase layering:2) Phase layering: the appearance or disappearancethe appearance or disappearance of minerals in the crystallization sequenceof minerals in the crystallization sequence developed in modal layersdeveloped in modal layers Phase layeringPhase layering … lafal syarri artinyaWebcryptic layering -layering based on variation in chemical composition of mineral phases -systematic variation in the chemical composition of certain minerals through a stratigraphic height of a layered sequence graded layering -gradual variation in either -mineralogy -grain size – quite rare in gabbroic LMIs Rhythmic layering lafal surat al kafirun