of stream-sediment and heavy-mineral-concentrate samples Open ...
of stream-sediment and heavy-mineral-concentrate samples Open ... of stream-sediment and heavy-mineral-concentrate samples Open ...
... CONTENTS Studies Related to AMRAP ............................................ 1 Introduction .............................................................. 1 Methods of Study ....................................................... 1 Sample Media ......................................................... 1 Sample Collection .................................................... 3 Stream-sediment samples ......................,................. 3 Heavy-mineral-concentrate samples ............................... 3 Sample Preparation ............................................... 3 Sample Analysis ................................................. 4 Spectrographic method ........................................... 4 Rock Analysis Storage System (RASS) ................. . .............. 4 Description of Data Tables ............................................ 4 References Cited ...................................................... 5 ILLUSTRATIONS Figure 1 . Location map of the Baird Mountains quadrangle. Alaska ......... 2 Plate 1 . Localities of stream-sediment and heavy-mi neral-concentrate samples from the Baird Mountains quadrangle. Alaska ........... in pocket TABLES Tab1 e 1 . Limits of determination for spectrographic analysi s of rocks and stream sediments ... ..................................... 6 Table 2 . Spectrographic analyses of stream-sediment samples from the Baird Mountains quadrangle. Alaska ................................... 7 Table 3 . Spectrographic analyses of heavy-mineral-concentrate samples from the Baird Mountains quadrangle. Alaska .......................... 75 Page
STUDIES RELATED TO AHRAP The U.S. Geological Survey is required by the Alaskan National Interests - Lands Conservation Act (Pub1 i c Law 96-487, 1980) to survey certain Federal lands to determine their mineral values, if. any.- Results from the Alaskan Mineral Resource Assessment Program (AMRAP) must be made available to the public and be submitted to the President and the Congress. This report presents spectrographic results of a geochemical survey of the Baird Mountains quadrangle, Alaska. INTRODUCTION In the sumners of 1983-85, we conducted a reconnaissance geochemical survey of the Baird Mountains quadr n le, Alask . The Baird Mountains quadrangle comprises about 5,600 mi $ (14,504 km !' ) in the Western Brooks Range in northwestern Alaska (fig. 1). The town of Kotzebue l'ies about 60 mi (96 km) southwest of the quadrangle. The northern part of the study area is included in the Noatak National Preserve and the eastern portion of the quadrangle is in the Kobuk National Park. Access to the study area is limited to air travel. The rocks in the Baird Mountains quadrangle consist mainly of low-grade metamorphosed Paleozoic marine carbonate, pel i tic, and clastic rocks with mi nor amounts of non-marine clastic rocks (Kar 1 and others, unpubl i shed mapping). Minor mafic and felsic volcanic and volcaniclastic rocks are locally intercalated within the Paleozoic sequences. Mesozoic marine sedimentary and mafic volcanic rocks overlie Paleozoic rocks in the northwestern part of the quadrangle. Medium-grade metamorphosed schists and intermediate composition intrusive rocks of Precambrian age are tectonically interleaved with lower-grade Paleozoic metasedimentary and metavolcanic rocks in the northeastern part of the quadrangle. Poly-deformed, mainly pelitic schists dominate the southern part of the quadrangle. Regional folding and thrusting during the Jurassic to Cretaceous Brooks Range orogeny has structurally complicated the rocks in the Baird Mountains, producing locally intense deformation and juxtaposing rocks of different metamorphic grade. Topographic relief is about 3,000 ft (914 m) with a maximum elevation of 4,760 ft (1,451 m) at Mt. Angayukaqsrak in the northeast corner of the quadrangle. The Baird Mountains are rugged and either barren or sparsely vegetated. Talus cover is extensive on steeper and poorly vegetated slopes. Lowlands are tundra-covered and at elevations below 1,000 ft (305 m) are sparsely forested. METHODS OF STUDY Sample kdia Analyses of the stream-sediment samples represent the chemistry of the rock material eroded from the drainage basin upstream from each sample site. Such information is useful in identifying those basins which contain concentrations of elements that may be related to mineral deposits. Analyses of heavy-mineral -concentrate samples provide i nformation about the composi tion of certain minerals in rock material eroded from the drainage basin upstream from each sample site. This selective concentration of minerals, many of which may be ore related, permits determination of some elements that are not easi ly detected in stream-sediment samples.
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...<br />
CONTENTS<br />
Studies Related to AMRAP ............................................ 1<br />
Introduction .............................................................. 1<br />
Methods <strong>of</strong> Study ....................................................... 1<br />
Sample Media ......................................................... 1<br />
Sample Collection .................................................... 3<br />
Stream-<strong>sediment</strong> <strong>samples</strong> ......................,................. 3<br />
Heavy-<strong>mineral</strong>-<strong>concentrate</strong> <strong>samples</strong> ............................... 3<br />
Sample Preparation ............................................... 3<br />
Sample Analysis ................................................. 4<br />
Spectrographic method ........................................... 4<br />
Rock Analysis Storage System (RASS) ................. . .............. 4<br />
Description <strong>of</strong> Data Tables ............................................ 4<br />
References Cited ...................................................... 5<br />
ILLUSTRATIONS<br />
Figure 1 . Location map <strong>of</strong> the Baird Mountains quadrangle. Alaska ......... 2<br />
Plate 1 . Localities <strong>of</strong> <strong>stream</strong>-<strong>sediment</strong> <strong>and</strong> <strong>heavy</strong>-mi neral-<strong>concentrate</strong><br />
<strong>samples</strong> from the Baird Mountains quadrangle. Alaska ........... in pocket<br />
TABLES<br />
Tab1 e 1 . Limits <strong>of</strong> determination for spectrographic analysi s <strong>of</strong><br />
rocks <strong>and</strong> <strong>stream</strong> <strong>sediment</strong>s ... ..................................... 6<br />
Table 2 . Spectrographic analyses <strong>of</strong> <strong>stream</strong>-<strong>sediment</strong> <strong>samples</strong> from the<br />
Baird Mountains quadrangle. Alaska ................................... 7<br />
Table 3 . Spectrographic analyses <strong>of</strong> <strong>heavy</strong>-<strong>mineral</strong>-<strong>concentrate</strong> <strong>samples</strong><br />
from the Baird Mountains quadrangle. Alaska .......................... 75<br />
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