J.W. Allingham
1964
<p><span>This study shows that </span>aeromagnetic<span> </span>anomalies<span> of less than 200 gammas are associated with topographic relief of exposed Precambrian granitic and volcanic rocks of the St. François Mountains. </span>Anomalies<span> resulting from hills coarsely crystalline granite are as high as 100 gammas </span>in<span> </span>amplitude<span>, whereas </span>anomalies<span> over comparable hills of fine-grained rocks, such as granophyre or devitrified volcanic rock, are as much as 200 gammas. </span>Anomalies<span> caused by normal faulting or shearing of igneous rocks have amplitudes of less than 100 gammas; they are observed best </span>in<span> profile. These </span>anomalies<span> are superposed on larger magnetic features related to pendants of volcanic rock </span>in<span> the roof of a granite batholith and are distinguished from large lateral variations </span>in<span> magnetic intensity by their </span>low<span> </span>amplitude<span> and small areal extent. Analyses of the compound </span>anomalies<span> yielded the subsurface configuration of isolated roof pendants of resistant extrusive rock </span>in<span> some areas. As many of these pendants have negligible remanent magnetization, induction theory was used </span>in<span> the analyses. Application of these results to the lead-mining areas shows that </span>aeromagnetic<span> patterns of </span>low<span> </span>amplitude<span> can guide mineral exploration </span>in<span> the region flanking the Ozark uplift, where isolated, buried hills of Precambrian igneous rocks controlled the development of some lead-bearing sedimentary structures </span>in<span> the overlying Cambrian carbonate strata. </span></p>
application/pdf
10.1190/1.1439390
en
Society of Exploration Geophysicists
Low-amplitude aeromagnetic anomalies in Southeastern Missouri
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