Feldspars inclusions

The largest collector surface for elements impinging on the Globe is the sea, of course. Heavy elements deposited in seawater are enriched in certain sediments such as manganese nodules, iron-manganese hydroxides. Fission tracks were found [83] in feldspar inclusions in such nodules, but no evidence was obtained [40,45] for spontaneous fission activities by counting nodules with neutron detectors. 

Subsequent examination of petrographic thin sections confirmed that the rock was igneous with a rhyolitelike composition made of a fine-grained quartz crystal matrix with feldspar inclusions. This material formed a large percentage of the fine-grained material from both coastal sites. This material constituted, however, only a very small percentage of the material from the inland site of Fiais (Table II). 

Fig. 2.3. Relation between the K+ and CI concentration of geothermal waters and inclusion fluids. The solid line defines the equilibrium condition between the solution and the assemblage albite-K-feldspar at 250°C. For symbols used, see caption to Fig. 2.2. (Shikazono, 1978a).

Limestone varieties differ greatly from one another in their texture and the impurities they contain, and consequently they also differ in color. The color of limestone may vary from white (when it contains practically no impurities) to off-white and even to intensely colored. Minor inclusions within the limestone structure are often of silica, usually in a concentration below 5%, as well as feldspar and clay in still lesser amounts. Many types of limestone also include embedded fossils. Much limestone deposits in the outer crust of the earth are altered during geologic metamorphic processes that involve mainly pressure and heat but also liquids and gases. Marble, for example, a metamorphic rock derived from calcium carbonate, is white when composed only of this substance colored metal ions and other impurities impart to marble a wide range of colors such as red, yellow, and green and also give... 

Table 5.62 Chemical analyses of some natural feldspars (Deer et al., 1983). (1) orthoclase (Mogok, Burma) (2) Adularia (St. Gottard, Switzerland) (3) anorthoclase inclusion in augite (Euganean Hills NE Italy) (4) sanidine from a nepheline-leucitite (5) albite from a pegmatite (6) anorthite from a calc-silicatic rock. ...

Lahradoriie is the characteristic feldspar of the more basic rock types like diorite. gahbro. andesite or basalt and it is usually associated with some one of the pyroxenes or amphiholes. Lahradoriie frequently shows a heauliful play of iridescent colors due lo minute inclusions of another mineral. However, the labradorescent phenomenon has not been fully determined. The classic location for this mineral is. of course. Labrador, whence its name. Il is a constituent there of the rock anorthosite and is found in the anorthosites of the Provinces of Quebec and Ontario, and in the Adirondack region in New York Stale. 

PERTHITE. An alkali feldspar comprising parallel or subparallel inlergrowths. The potassium-nch phase, usually microcline, seems to be the host from which the sodium-rich phase, usually albite inclusions, exsolved. The exsolved areas typically form blebs, films, lamellae, small strings, or irregular veinlets and usually are visible to the naked eye. 

Jessberger, E. K., Ostertag, R. (1982) Shock effects on the K-Ar system of plagioclase feldspar and the age of inclusions from North-eastern Minnesota. Geochim. Cosmochim. Acta, 46, 1465-71. 

Petrographic comparison of the Mexico City majolica with Teotihuacan sherds shows that except for the secondary deposition of carbonates, which is present in the majolica but absent in the Precolumbian sherds, the mineral composition of both sets of specimens is very similar. Both notably include hornblende and similar feldspars as inclusions, and both are low in quartz. Similarly, except for the calcite in the majolica, both sets of sherds show similar x-ray diflFraction patterns. The mineralogical evidence, therefore, strongly suggests that both sets of sherds were made from closely related clays and that the compositional diflEerences that exist between them are primarly the result of the accumulation of a secondary calcareous deposit within the majolica sherds during burial in the wet soil of Mexico City. 

Chassigny is the only known martian dunite. It is an olivine-chromite cumulate consisting of 90% olivine (Fa. 32), 5% pyroxene, 2% feldspar (An 2o) that has been transformed into maskelynite, and 3% accessory minerals including chromite (Figure 30(d)). Melt inclusions in olivine contain hydrous amphibole. 

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