GMAT考试资料：GWD试题合集（十五）.

　　以下将为正在备战GMAT考试的同学们整理一些经典的GMAT阅读试题，并分多个合集推出，希望能够为正在备考GMAT考试的考生提供或多或少的帮助。

　　8. GWD-6-Q23 to Q26寻找钻石的新思路

　　Diamonds are almost impos-

　　sible to detect directly because they

　　are so rare: very rich kimberlite

　　Line pipes, the routes through which

　　(5) diamonds rise, may contain only

　　three carats of diamonds per ton

　　of kimberlite. Kimberlite begins as

　　magma in Earth’s mantle (the layer

　　between the crust and the core). As

　　(10) the magma smashes through layers

　　of rock, it rips out debris, creating

　　a mix of liquid and solid material.

　　Some of the solid material it brings

　　up may come from a so-called

　　(15) diamond-stability field, where condi-

　　tions of pressure and temperature

　　are conducive to the formation of

　　diamonds. If diamonds are to sur-

　　vive, though, they must shoot toward

　　(20) Earth’s surface quickly. Otherwise,

　　they revert to graphite or burn.

　　Explorers seeking diamonds look

　　for specks of “indicator minerals”

　　peculiar to the mantle but carried up

　　(25) in greater quantities than diamonds

　　and eroded out of kimberlite pipes

　　into the surrounding land. The stan-

　　dard ones are garnets, chromites,

　　and ilmenites. One can spend years

　　(30) searching for indicators and tracing

　　them back to the pipes that are their

　　source; however, 90 percent of

　　kimberlite pipes found this way are

　　barren of diamonds, and the rest

　　(35) are usually too sparse to mine.钻石的形成过程及探察方法：寻找indicator …

　　In the 1970’s the process of

　　locating profitable pipes was rined

　　by focusing on the subtle differ-

　　ences between the chemical

　　(40) signatures of indicator minerals

　　found in diamond-rich pipes as

　　opposed to those found in barren

　　pipes. For example, G10 garnets,

　　a type of garnet typically found in

　　(45) diamond-rich pipes, are lower in

　　calcium and higher in chrome than

　　garnets from barren pipes. Geo-

　　chemists John Gurney showed that

　　garnets with this composition were

　　(50) formed only in the diamond-stability

　　field; more commonly found ver-

　　sions came from elsewhere in the

　　mantle. Gurney also found that

　　though ilmenites did not form in the

　　(55) diamond-stability field, there was a

　　link usul for prospectors: when

　　the iron in ilmenite was highly

　　oxidized, its source pipe rarely

　　contained any diamonds. He rea-

　　(60) soned that iron took on more or less

　　oxygen in response to conditions in

　　the kimberlitic magma itself—mainly

　　in response to heat and the avail-

　　able oxygen. When iron became

　　(65) highly oxidized, so did diamonds;

　　that is, they vaporized into carbon

　　dioxide. 1970年代方法的转变

　　问题解决

　　逻辑简图：

　　1P: very rich K may contain….. explorers seeking for diamonds look for indicator mineral, however….

　　2P: 1970’s, process redined by focusing on subtle difference….. JG showed; also found… reasoned…….

　　以上就是本期GMAT试题的所有内容，考生可以此为据并进行针对性的练习，逐步掌握GMAT阅读的解题规律及技巧，以达到迅速提高GMAT考试成绩的目的。 相关链接：

1.GMAT考试资料：GWD试题合集（十四）

2.GMAT考试资料：GWD试题合集（十三）

3.GMAT考试资料：GWD试题合集（十二）

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