Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Free via Open Access: OA OA Abstract OA Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mars, J. C. Articles by Rowan, L. C. Search for Related Content GeoRef GeoRef Citation

Regional mapping of phyllic- and argillic-altered rocks in the Zagros magmatic arc, Iran, using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and logical operator algorithms

¹ U.S. Geological Survey, National Center, Mail Stop 954, Reston, Virginia 20192, USA

View larger version (48K): [in this window] [in a new window]   Figure 1. Illustrated deposit model of a porphyry copper deposit (modified from Lowell and Guilbert, 1970). (A) Schematic cross section of hydrothermal alteration minerals and types, which include propylitic, phyllic, argillic, and potassic alteration. (B) Schematic cross section of ores associated with each alteration type.

View larger version (16K): [in this window] [in a new window]   Figure 2. Laboratory spectra of epidote, calcite, muscovite, kaolinite, chlorite, and alunite, which are common hydrothermal alteration minerals (Clark et al., 1993b). Alunite and kaolinite have Al-O-H absorption features at 2.17 and 2.20 µm. Muscovite has a prominent Al-O-H 2.20 µm absorption feature and a secondary 2.35 µm absorption feature. Chlorite and epi-dote have an Fe-Mg-O-H 2.32 µm absorption feature and a broad Fe2+ feature from 1.65 to 0.6 µm. Calcite has a prominent 2.33 µm CO3 absorption feature.

View larger version (23K): [in this window] [in a new window]   Figure 3. Location map of the Tertiary volcanic and igneous intrusive rocks of the Zagros magmatic arc and outline of Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) scenes used to map hydrothermally altered rocks. The Sabzevaran and Gowk strike-slip fault systems and the Makran transfer zone are defined as the Zagros-Makran transform zone (yellow dashed lines), which divides the active southeastern part of the magmatic arc from the dormant northwestern part of the arc (Regard et al., 2004; Walker and Jackson, 2002).

View larger version (20K): [in this window] [in a new window]   Figure 4. (A) Laboratory spectra of limonite, calcite, kaolinite, and alunite resampled to Landsat Multispectral Scanner (MSS), Thematic Mapper (TM), and Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) bandpasses. (B) Laboratory spectra of limonite, muscovite, kaolinite, alunite, epidote, calcite, and chlorite resampled to ASTER bandpasses. Spectra include limonite with a broad 0.66–1.165 µm absorption feature; muscovite, typical in phyllic alteration, with a 2.20 µm absorption feature; kaolinite and alunite, which are common in argillic alteration, have 2.165 and 2.20 µm absorption features; and epidote, calcite, and chlorite, which are typically associated with propylitic alteration and display 2.32, 2.33, and 2.32 µm absorption features, respectively. Epidote and chlorite have a broad Fe2+ absorption feature that affects ASTER bands 2, 3, and 4 (0.66–1.65 µm). The numbers across the top of the graph indicate the ASTER band center positions (Clark et al., 1993b).

View larger version (12K): [in this window] [in a new window]   Figure 4. (A) Laboratory spectra of limonite, calcite, kaolinite, and alunite resampled to Landsat Multispectral Scanner (MSS), Thematic Mapper (TM), and Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) bandpasses. (B) Laboratory spectra of limonite, muscovite, kaolinite, alunite, epidote, calcite, and chlorite resampled to ASTER bandpasses. Spectra include limonite with a broad 0.66–1.165 µm absorption feature; muscovite, typical in phyllic alteration, with a 2.20 µm absorption feature; kaolinite and alunite, which are common in argillic alteration, have 2.165 and 2.20 µm absorption features; and epidote, calcite, and chlorite, which are typically associated with propylitic alteration and display 2.32, 2.33, and 2.32 µm absorption features, respectively. Epidote and chlorite have a broad Fe2+ absorption feature that affects ASTER bands 2, 3, and 4 (0.66–1.65 µm). The numbers across the top of the graph indicate the ASTER band center positions (Clark et al., 1993b).

View larger version (123K): [in this window] [in a new window]   Figure 5. Index map of Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) scenes for the Iran study area. The first two numbers in each scene label are 07, which indicate that the type of scene is an AST_07 reflectance product obtained from the EROS Data Center. The next 6 numbers in each scene label indicate year, month, and day. Some labels have a letter at the end of the scene label to distinguish between scenes taken on the same day.

View larger version (18K): [in this window] [in a new window]   Figure 6. Spectra of playa from Cuprite, Nevada. Airborne Visible Infrared Imaging Spectrometer (AVIRIS) and in situ field spectra illustrate a slight 2.20 µm absorption feature. The AST_07 spectrum of the same playa illustrates that band 5 (red arrows) is 10–15% lower than the AVIRIS or in situ field spectra in relation to band 6. The AST_07 spectrum erroneously has a similar shape to alunite spectra illustrated in Figure 10. The numbers across the top of the graph indicate the ASTER band center positions.

View larger version (13K): [in this window] [in a new window]   Figure 7. Laboratory spectra of muscovite, kaolinite, and alunite resampled to Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) bandpasses. The spectra illustrate the positions and intensities of absorption features in the 2.0–2.5 µm region used to define ratios in the argillic and phyllic mapping algorithms. The muscovite spectrum displays a 2.20 µm absorption feature, whereas kaolinite and alunite exhibit 2.17 and 2.20 µm absorption features. The numbers across the top of the graph indicate the ASTER band center positions (Clark et al., 1993b).

View larger version (8K): [in this window] [in a new window]   Figure 8. Relative band depth (RBD) ratio schematic (modified from Crowley et al., 1989).

View larger version (17K): [in this window] [in a new window]   Figure 9. Laboratory and Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) spectra of dry sagebrush. The arrows indicate locations of cellulose absorption features. Prominent 2.165 (ASTER band 5) and 2.33 (ASTER band 8) µm absorption features are documented in the ASTER spectrum. The numbers across the top of the graph indicate the ASTER band center positions.

View larger version (29K): [in this window] [in a new window]   Figure 10. (A) The logical operator algorithm that maps argillic-altered rocks using band ratios 4/5, 5/6, and 7/6, which define the 2.17 µm absorption feature. (B) The logical operator algorithm that maps phyllic-altered rocks using band ratios 4/6, 5/6, and 7/6, which define the 2.20 µm absorption feature. Pixels with green vegetation and low reflectance (dark pixels) are masked in the argillic and phyllic logical operator algorithms using a band ratio of 3/2 and band 4 threshold, respectively.

View larger version (24K): [in this window] [in a new window]   Figure 11. An Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) image of a granite outcrop and reflectance spectra from three locations. Spectra A and C were taken from sun-illuminated areas and illustrate a slight 2.20 µm absorption feature typical of spectra typical for muscovite-bearing granite. Spectrum B, taken from an area that consists of granite, however, is shaded. This results in anomalously high band 5 and band 9 reflectance values and produces incorrect and prominent 2.20 and 2.33 µm absorption features.

View larger version (31K): [in this window] [in a new window]   Figure 12. Generalized map showing the distribution of silicified (red map unit), opalized (blue map unit), and argillized (yellow map unit) rocks at Cuprite, Nevada (modified from Ashley and Abrams, 1980); inset map shows location of area in southern Nevada.

View larger version (29K): [in this window] [in a new window]   Figure 13. Generalized geologic map of the Cuprite mining district, Nevada. Qal—sand, gravel, and boulders; Qp—playa deposits; Tb2—olivine basalt; Tsf—sodic ash-flow tuff; Tb1—porphyritic olivine basalt; Ts—crystal-rich rhyolite and latite tuff, conglomerate, and sandstone; Tf—quartz latitic felsite; Ce—limestone and chert; Cms—limestone and limey siltstone; Ch—phyllitic siltstone and minor sandy limestone (modified from Ashley and Abrams, 1980; Swayze, 1997); inset map shows location of area in southern Nevada.

View larger version (106K): [in this window] [in a new window]   Figure 14. Maps of argillic and phyllic rocks at Cuprite, Nevada, using logical operator algorithms: (1) Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) argillic alteration, (2) ASTER-simulated (AVIRIS) argillic alteration, (3) ASTER phyllic rocks, and (4) ASTER-simulated (AVIRIS) phyllic rocks. Phyllic and argillic units are superimposed on ASTER and ASTER-simulated band 3 images.

View larger version (17K): [in this window] [in a new window]   Figure 15. Average spectra of argillic and phyllic spectral units for Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) and ASTER-simulated (AVIRIS resampled to ASTER bandpasses) data.

View larger version (58K): [in this window] [in a new window]   Figure 16. (A) Geologic map (modified from Huber, 1969a) and (B) a Landsat Thematic Mapper (TM) band 7 image with argillic and phyllic alteration units in the northwestern part of the study area mapped. Location of figure is shown on Plate 2.

View larger version (67K): [in this window] [in a new window]   Figure 17 (on this and previous page). (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the area around the Meiduk copper mine, Iran, in the central part of the study area (modified from Huber, 1969a). Location of figure is shown on Plate 2.

View larger version (134K): [in this window] [in a new window]   Figure 17. Continued.

View larger version (54K): [in this window] [in a new window]   Figure 18. (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the area around the Sar Cheshmeh Copper Mine, Iran, in the central part of the study area (modified from Huber, 1969a). Location of figure is shown on Plate 2.

View larger version (123K): [in this window] [in a new window]   Figure 18. (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the area around the Sar Cheshmeh Copper Mine, Iran, in the central part of the study area (modified from Huber, 1969a). Location of figure is shown on Plate 2.

View larger version (74K): [in this window] [in a new window]   Figure 19. (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the Zagros-Makran transform zone, in the south-central part of the study area (modified from Huber, 1969b). Location of figure is shown on Plate 2.

View larger version (61K): [in this window] [in a new window]   Figure 20. (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the area southeast of the Zagros-Makran transform zone, in the south-central part of the study area (modified from Huber, 1969b). Location of figure is shown on Plate 2.

View larger version (61K): [in this window] [in a new window]   Figure 21 (on this and previous page). (A) Geologic map and (B) Landsat Thematic Mapper (TM) band 7 image with mapped argillic and phyllic alteration of the southeastern part of the Zagros magmatic arc (modified from Huber, 1969b). Location of figure is shown on Plate 2.

View larger version (132K): [in this window] [in a new window]   Figure 21. Continued.

View larger version (14K): [in this window] [in a new window]   Figure 22. Histogram of percent alteration within a 1 km radius of 60 mine and occurrence sites in the central part of the study area.

View larger version (84K): [in this window] [in a new window]   Plate 1. Orthorectified Landsat Thematic Mapper (TM) band 7 of the Zagros magmatic arc, Iran, with phyllic and argillic alteration units compiled from Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) data. Numbers indicate potential porphyry copper deposits determined from alteration spectral units (*mine at location). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00044.PL1 or the full-text article on www.gsajournals.org to view the full-size plate.

View larger version (89K): [in this window] [in a new window]   Plate 2. Orthorectified Landsat Thematic Mapper (TM) band 7 of the Zagros magmatic arc, Iran, with alteration, mines, occurrences, figure locations, and Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) and geologic map coverage. If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00044.PL2 or the full-text article on www.gsajournals.org to view the full-size plate.