Intermediate Rock

Intermediate Rock

 

igneous rock containing 56–65 percent silica. This category includes primarily feldspathic rocks with small admixtures of such ferromagnesian minerals as pyroxene, hornblende, and, more rarely, biotite. Intermediate plagioclases (oligoclase, andesine) are typical of feldspars. According to the weight percentage of the constituents of intermediate rocks, a distinction is made between the sodium series (diorites, andésites, porphyrites) and the calcic series (syenites, trachytes).

Intermediate rocks are found mainly among extrusive rocks in which andésites and porphyrites predominate over trachytes and porphyries; the intrusive rocks (diorite, syenite) are much less widely distributed.

References in periodicals archive ?
A four-hour techniques clinic for beginning and intermediate rock climbers will be held Saturday at 10 a.
The dispersion maps confirm this incompatible pateerns of elements of second group, such that concentration of these elements Increases of the ultramafic rocks to the mafic and intermediate rocks of the southern study area.
Ttitanium, copper, silver and arsenic elements have dispersion than together and similar geochemical characteristics, such that concentration of these elements increases of the ultramafic rocks to the mafic and intermediate rocks .
An alternative model could be that these intermediate rocks resulted from the magmatic differentiation of mafic arc magmas (crystal fractionation, crustal contamination).
Type Basic rocks Intermediate rocks Sample AN20 AN48 AN24 AN25 AN22 Major elements (wt %) Si[O.
The Silurian-Devonian Fogo Island Batholith, Newfoundland, is examined by Ken Currie, who shows that the sill-like bimodal body has a complex history including a late influx of mafic magma that resulted in hybrid intermediate rocks.
After the application of DODESSYS, the statistics of compositional data (number of samples, mean, and standard deviation) from each region are summarized in Tables 25, 26, and 27 for ultrabasic, basic, and intermediate rocks, respectively (Appendix A--Supplementary material).
Intermediate rocks are present in all regions compiled in this study.

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