课程咨询

GRE首页 GRE课程 GRE动态 0元讲座 GRE模考网站

新东方在线 > GRE > GRE阅读 > 正文
扫码关注掌握一手留学资讯

扫码关注掌握一手留学资讯

回复XDF免费领

水平测试和备考资料

扫码关注公众号

GRE阅读:钻石

2017-01-29 15:33:00来源：!新东方在线

　　GRE阅读:钻石

　　Diamonds, an occasional component of rare igneous rocks called lamproites and kimberlites, have never been dated satisfactorily. However, some diamonds contain minute inclusions of silicate minerals, commonly olivine, pyroxene, and garnet. These minerals can be dated by radioactive decay techniques because of the very small quantities of radioactive trace elements they, in turn, contain. Usually, it is possible to conclude that the inclusions are older than their diamond hosts, but with little indication of the time interval involved. Sometimes, however, the crystal form of the silicate inclusions is observed to resemble more closely the internal structure of diamond than that of other silicate minerals. It is not known how rare this resemblance is, or whether it is most often seen in inclusions of silicates such as garnet, whose crystallography is generally somewhat similar to that of diamond; but when present, the resemblance is regarded as compelling evidence that the diamonds and inclusions are truly cogenetic.

　　17. The author implies that silicate inclusions were most often formed

　　(A) with small diamonds inside of them

　　(B) with trace elements derived from their host minerals

　　(C) by the radioactive decay of rare igneous rocks

　　(D) at an earlier period than were their host minerals(D)

　　(E) from the crystallization of rare igneous material

　　18. According to the passage, the age of silicate minerals included in diamonds can be determined due to a feature of the

　　(A) trace elements in the diamond hosts

　　(B) trace elements in the rock surrounding the diamonds

　　(C) trace elements in the silicate minerals

　　(D) silicate minerals’ crystal structure(C)

　　(E) host diamonds’ crystal structure

　　19. The author states that which of the following generally has a crystal structure similar to that of diamond?

　　(A) Lamproite

　　(B) Kimberlite

　　(C) Olivine

　　(D) Pyroxene(E)

　　(E) Garnet

　　20. The main purpose of the passage is to

　　(A) explain why it has not been possible to determine the age of diamonds

　　(B) explain how it might be possible to date some diamonds

　　(C) compare two alternative approaches to determining the age of diamonds

　　(D) compare a method of dating diamonds with a method used to date certain silicate minerals(B)

　　(E) compare the age of diamonds with that of certain silicate minerals contained within them

本文关键字: GRE阅读 GRE阅读真题

添加新东方美研助教回复【GRE】获取

模考真题|写作题库|阅读机经|佛脚词汇

更多资料

添加美研助教号，
回复【GRE】获取备考必看资料包

  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加美研助教号】，回复对应关键字领取学习资料。
更多>>
更多内容

关注新东方美研助教

回复【GRE】获取备考必看资料包

新东方美研备考资料
GRE/GMAT直播精讲小班 GRE/GMAT精讲智能系统课 托福直播/精讲课（30天/60天）
更多>>
更多惊喜>>

添加美研助教号，
回复【GRE】获取备考必看资料包

  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加美研助教号】，回复对应关键字领取学习资料。
更多>>
更多资料
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10