阅读36套 E12 第7题
7. It can be inferred from the passage that the use
of flux in processing copper ore can alter the
lead isotope composition of the resulting metal
EXCEPT when
(A) there is a smaller concentration of lead in
the flux than in the copper ore
(B) the concentration of lead in the flux is
equivalent to that of the lead in the ore
(C) some of the lead in the flux evaporates
during processing
(D) any lead in the flux has the same isotopic
composition as the lead in the ore
(E) other metals are added during processing
The determination of the sources of copper ore used in
the manufacture of copper and bronze artifacts of Bronze
Age civilizations would add greatly to our knowledge of
cultural contacts and trade in that era. Researchers have
5 analyzed artifacts and ores for their concentrations of elements,
but for a variety of reasons, these studies have generally failed
to provide evidence of the sources of the copper used in the
objects. Elemental composition can vary within the same
copper-ore lode, usually because of varying admixtures of
10 other elements, especially iron, lead, zinc, and arsenic. And
high concentrations of cobalt or zinc, noticed in some artifacts,
appear in a variety of copper-ore sources. Moreover, the
processing of ores introduced poorly controlled changes
in the concentrations of minor and trace elements in the
15 resulting metal. Some elements evaporate during smelting
and roasting; different temperatures and processes produce
different degrees of loss. Finally, flux, which is sometimes
added during smelting to remove waste material from the
ore, could add quantities of elements to the final product.
20 An elemental property that is unchanged through these
chemical processes is the isotopic composition of each
metallic element in the ore. Isotopic composition, the
percentages of the different isotopes of an element in a given
sample of the element, is therefore particularly suitable as an
25 indicator of the sources of the ore. Of course, for this purpose
it is necessary to find an element whose isotopic composition
is more or less constant throughout a given ore body, but
varies from one copper ore body to another or, at least, from
one geographic region to another.
30 The ideal choice, when isotopic composition is used to
investigate the source of copper ore, would seem to be copper
itself. It has been shown that small but measurable variations
occur naturally in the isotopic composition of copper.
However, the variations are large enough only in rare
35 ores; between samples of the common ore minerals of copper,
isotopic variations greater than the measurement error have
not been found. An alternative choice is lead, which occurs
in most copper and bronze artifacts of the Bronze Age in
amounts consistent with the lead being derived from the
40 copper ores and possibly from the fluxes. The isotopic
composition of lead often varies from one source of
common copper ore to another, with variations exceeding
the measurement error; and preliminary studies indicate
virtually uniform isotopic composition of the lead from a
45 single copper-ore source. While some of the lead found in
an artifact may have been introduced from flux or when
other metals were added to the copper ore, lead so added in
Bronze Age processing would usually have the same isotopic
composition as the lead in the copper ore. Lead isotope
50 studies may thus prove useful for interpreting the
archaeological record of the Bronze Age. 作者: 裤子李 时间: 2012-9-20 14:32:44
这就是个细节题嘛。你看这句话:The isotopic composition of lead often varies from one source of common copper ore to another, with variations exceeding the measurement error; and preliminary studies indicate virtually uniform isotopic composition of the lead from a single copper-ore source.(L40的):Lead同位素大多在铜矿和铜矿之间不同;而研究表明lead同位素在来自于同一个铜矿是完全相同(virtually uniform )
题目问的是:除了那种情况外,加入flux会改变同位素成分。其实就是问那种情况不会改变同位素嘛
L45又说:some of the lead found in an artifact may have been introduced from flux .Lead又是来自于flux的
所以,不会改变同位素的情况当然就是:lead来自于同一个铜矿的时候了,具有相同同位素。
其实D的any应该对应是“virtually uniform ”,题目中的some只是说了lead一部分来自于flux,D的any lead 是说在来自于flux的lead里面的any lead。所以不影响啊。
反之“如果原文说some flux 中又lead,这个any绝对化就错了。