- UID
- 148222
- 在线时间
- 小时
- 注册时间
- 2006-3-26
- 最后登录
- 1970-1-1
- 主题
- 帖子
- 性别
- 保密
|
According to a recent theory, Archean-age
gold-quartz vein systems were formed more than
two billion years ago from magmatic fluids that
originated from molten granite-like bodies deep
beneath the surface of the Earth. This theory is
contrary to the widely held view that the systems
were deposited from metamorphic fluids, that is,
from fluids that formed during the dehydration of
wet sedimentary rocks.
The recently developed theory has considerable
practical importance. Most of the gold deposits
discovered during the original gold rushes were
exposed at the Earth’s surface and were found
because they had shed trails of alluvial gold
that were easily traced by simple prospecting
methods. Although these same methods still lead
to an occasional discovery, most deposits not yet
discovered have gone undetected because they are
buried and have no surface expression.
The challenge in exploration is therefore to
unravel the subsurface geology of an area and
pinpoint the position of buried minerals. Methods
widely used today include analysis of aerial images
that yield a broad geological overview; geophysical
techniques that provide data on the magnetic,
electrical, and mineralogical properties of the
rocks being investigated; and sensitive chemical
tests that are able to detect the subtle chemical
halos that often envelop mineralization. However,
none of these high-technology methods are of any
value if the sites to which they are applied have
never mineralized, and to maximize the chances of
discovery the explorer must therefore pay particular
attention to selecting the ground formations most
likely to be mineralized. Such ground selection relies
to varying degrees on conceptual models, which
take into account theoretical studies of relevant
factors.
These models are constructed primarily from
empirical observations of known mineral deposits
and from theories of ore-forming processes.
The explorer uses the models to identify those
geological features that are critical to the formation
of the mineralization being modeled, and then tries
to select areas for exploration that exhibit as many
of the critical features as possible.
111. Which of the following statements about discoveries
of gold deposits is supported by information in the
passage?
(A) The number of gold discoveries made annually
has increased between the time of the original
gold rushes and the present.
(B) New discoveries of gold deposits are likely to be
the result of exploration techniques designed to
locate buried mineralization.
(C) It is unlikely that newly discovered gold deposits
will ever yield as much as did those deposits
discovered during the original gold rushes.
(D) Modern explorers are divided on the question of
the utility of simple prospecting methods as a
source of new discoveries of gold deposits.
(E) Models based on the theory that gold originated
from magmatic fluids have already led to new
discoveries of gold deposits.
这道题目我是用排除法做的，觉得B选项最靠近正确，不过还是觉得也有问题。因为文章当中说的是这些none of these high technology methods are of any value if the sites to which they are applied have never mineralized，而去定位这些mineralization的是conceptual model。而B选项是说这些techniques designed to locate buried mineralization
1
还请大家帮忙指点一些，我理解的哪里有问题啦~ |
|
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2010-10-17 13:32:14
收藏
收藏
