Calcium-aluminum inclusions formation

Calcium—Silicon. Calcium—silicon and calcium—barium—siUcon are made in the submerged-arc electric furnace by carbon reduction of lime, sihca rock, and barites. Commercial calcium—silicon contains 28—32% calcium, 60—65% siUcon, and 3% iron (max). Barium-bearing alloys contains 16—20% calcium, 9—12% barium, and 53—59% sihcon. Calcium can also be added as an ahoy containing 10—13% calcium, 14—18% barium, 19—21% aluminum, and 38—40% shicon These ahoys are used to deoxidize and degasify steel. They produce complex calcium shicate inclusions that are minimally harm fill to physical properties and prevent the formation of alumina-type inclusions, a principal source of fatigue failure in highly stressed ahoy steels. As a sulfide former, they promote random distribution of sulfides, thereby minimizing chain-type inclusions. In cast iron, they are used as an inoculant. 

Calcium-aluminum-rich inclusions (CAIs) After removing the progressive mass-dependent fractionation that occurs in the measuring process and in the formation process for the samples, isotopic anomalies for 66Zn are observed in certain... 

Calcium-aluminum-rich inclusions (CAIs) After removing the progressive mass-dependent fractionation that occurs in the measuring process and in the formation process for the samples, isotopic anomalies for 7°Zn are observed in certain types of CAIs ( FUN inclusions). Only one detection exists to date, a deficit of 2 parts per thousand for 7°Zn in one FUN inclusion. An excess of 1.7 parts per thousand for 66Zn exists in that same CAI. Some form of cosmic chemical memory (see Glossary) is probably involved. 

Ma (Wadhwa et al. 2007 and references therein), which is actually the age of a group of inclusions within chondrites known as calcium-aluminum-rich inclusions (CAIs). The word primitive refers to the fact that the bulk compositions of all chondrites, within a factor of two, are solar in composition for all but the most volatile elements (Weisberg et al. 2006). This fact indicates that chondrites have not been through a planetary melting or differentiation process in their parent body, indicating that they have recorded the materials that were present and the processes that operated within the disk before or during planet formation. 

The MIF phenomenon was first observed by Clayton in 1973 for the isotopic oxygen content in the earliest solids in the solar system, the so-called calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondritic meteorites [1]. The slope of versus plot for the CAIs was close to unity, the CAIs being equally deficient in the heavy O isotopes, deficient in the S notation sense, while the ozone is equally enriched in those isotopes in that sense, as in Figure 2.2. Both are examples of an MIF. Interest in this striking phenomenon for the CAIs is motivated by what it may reveal about the formation of the early solar system. Standard reaction rate transition state theory [3], and behavior of oxygen an other isotope fractionation in many other systems, would have led, instead, to the slope... 

Wark D. and Boynton W. V. (2001) The formation of rims on calcium-aluminum-rich inclusions Step 1. Flash heating. Meteorit. Planet. Sci. 36, 1135-1166. 

The original building blocks of the Earth are thought to be preserved in a group of primitive meteorites known as the carbonaceous chondrites. These contain inclusions rich in calcium-aluminum minerals which formed at high temperature within 104-105 years of the formation of the solar system. Also present are chondrules, olivine-rich spheroidal melt droplets, a few millimeters in diameter, which formed within the first 4 Ma of Solar System history. 

Iodine-xenon experiments have also been applied, but only with minimal success, to dating the formation of chondrules and calcium-aluminum-rich inclusions (Fig. 5). These two types of objects make up large portions of many meteorites, and are believed to be among the earliest solids formed in the solar nebula. 

There are two types of refractory inclusions calcium- and aluminum-rich inclusions (this section) and amoeboid olivine aggregates (Section 1.07.5.3). Since the mineralogy, chemistry and isotope chemistry of refractory inclusions were reviewed by MacPherson et al. (1988), many new analyses have been made of CAIs in CV, CM, CO, CR, CH, CB, ordinary and enstatite chondrites that provide important constraints on physicochemical conditions, time, and place of CAI formation. CAIs are addressed in detail in Chapter 1.08, the role of condensation and evaporation in their formation in Chapter 1.15, and their clues to early solar system chronology in Chapter 1.16. 

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