Intermediate Rock

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Host rocks to the mineralisation are talc-chlorite schist, amphibolite schist and intermediate rock types.
Physiological and psychological responses to lead and top rope climbing for intermediate rock climbers.
Fitzpatrick et al., "Climbing-specific finger endurance: a comparative study of intermediate rock climbers, rowers and aerobically trained individuals," Journal of Sports Sciences, vol.
Blackwell, "Physiological and psychological responses to lead and top rope climbing for intermediate rock climbers," European Journal of Sport Science, vol.
A four-hour techniques clinic for beginning and intermediate rock climbers will be held Saturday at 10 a.m.
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).
In the interval down to a depth of 5.5 km a uniform sequence of volcanoclastic basic and intermediate rocks has been cut.
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. In the last paper of the set, by David Gibson, Dan Lux and Michael Choate, petrographic evidence from the Mount Waldo granite in Maine indicates that mafic inputs fuelled mixing and convection in this magma chamber comparable to that evident in the older suite of plutons that crop out along the Maine coast.
Namely, felsic rocks have the lowest [kappa] and NRM values, followed by intermediate rocks, and mafic rocks show the highest [kappa] and NRM values (Table 3 and Figures 5(b) and 5(c)).
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).

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