CCAM line
The CCAM line is a line on oxygen isotope plots defined by anhydrous minerals of carbonaceous chondrites, with a slope near 1.
The CCAM line, short for carbonaceous chondrite anhydrous mineral line, was defined in the 1970s by measurements of water-free minerals separated from carbonaceous chondrites, especially CAIs and chondrules from Allende. On a three-oxygen isotope graph, they fall on a line with a slope of about 0.94, quite different from the terrestrial slope of about 0.52.
A line of slope near 1 means oxygen-17 and oxygen-18 change together by similar amounts. That is the signature of mixing between an oxygen-16-rich component and a component depleted in it, rather than mass-dependent sorting. A closely related line with slope 1.0, often called the primitive chondrule mineral line, was later defined from very primitive chondrules.
The CCAM line was one of the first clues that the early Solar System contained oxygen reservoirs of different isotopic makeup. The discovery, by Robert Clayton and colleagues in 1973, launched oxygen isotope studies as a major tool in meteorite classification.
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