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1、学习 - 好资料General English Admission Test For Non-English MajorPh.D. program(Harbin Institute of Technology)Passage OneQuestions 1-7 are based on the following passage:According to a recent theory, Archean-age gold-quartz vein systemswere formed over two billion years ago from magmatic fluids that orig
2、inated from molten granitelike 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 co
3、nsiderable practical importance. Most of the gold deposits discovered during theoriginal gold rushes were exposed at the Earth s surface and were found because theyhad shed trails of alluvial gold that were easily traced by simple prospecting methods.Although these same methods still leas to an occa
4、sional discovery, most deposits not yetdiscovered havegone undetected because they areburied andhavenosurfaceexpression.The challenge in exploration is therefore to unravel the subsurface geology of anarea and pinpoint the position of buried minerals. Methods widely used today includeanalysis of aer
5、ial images that yield a broad geological overview, geophysical techniquesthat provide data on the magnetic, electrical, and mineralogical properties of the rocksbeing investigated, and sensitive chemical tests thatare able to detect : the subtlechemical halosthat often envelop mineralization. Howeve
6、r,noneofthesehigh-technology methods are of any value if the sites to which they are applied havenever 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 re
7、lies 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 themodels to identify those geologi
8、cal 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.1. The author is primarily concerned with.A. advocating a return to an older methodology.B. explaining the imp
9、ortance of a recent theory.C. enumerating differences between two widely used methods D. describing events leading to a discovery2. According to passage, the widely held view of Archean-age gold-quartz vein更多精品文档学习 - 好资料systems is that such systemsA were formed from metamorphic fluids.B originated i
10、n molten granitelike bodiesC were formed from alluvial depositsD generally have surface expression3. The passage implies that which of the following steps would be the first performed by explorers who wish to maximize their chances of discovering gold?A Surveying several sites known to have been for
11、med more than two billion years ago.B Limiting exploration to sites known to have been formed form metamorphic fluid.C Using an appropriate conceptual model to select a site for further exploration.D Using geophysical methods to analyze rocks over a broad area.4. Which of the following statements ab
12、out discoveriesof golddeposits is supported by information in the passage?A The number of gold discover made annually has increased between the time of the original gold rushes and the presentB New discoveries of gold deposits are likely to be the result of exploration techniques designed to locate
13、buried mineralizationC 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 deposi
14、ts.5. It can be inferred from the passage that which of the following is easiest todetect?A A gold-quartz vein system originating in magma tic fluids.B A gold-quartz vein system originating in metamorphic fluids. C A gold deposit that is mixed with granite.D A gold deposit that has shed alluvial gol
15、d.6. The theory mentioned in line I relates to the conceptual models discussed in the passage in which of the following ways?A It may furnish a valid account of ore-forming processes,and hence, can support conceptual models that have great practical significance.B It suggests that certain geological formations, long believed to be mineralized, are in fact mineralized thus confirming current conceptual models.C. It suggeststhat there may not be enough similarity across Archean-agegold-quartz vein systems to warrant the formula
