بارزسازی دگرسانی‌های گرمابی در تصاویر استر منطقه سرچشمه با استفاده از عملگرهای منطقی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری بخش مهندسی معدن دانشگاه شهید باهنر کرمان

2 استاد بخش مهندسی معدن دانشگاه شهید باهنر کرمان

10.29252/anm.7.14.61

چکیده

در این تحقیق، از تصاویر ماهواره‌ای استر و الگوریتم ترکیبی نسبت‌های باندی با روش عملگرهای منطقی با تعیین حد آستانه بر اساس مطالعات زمینی، آزمایشگاهی و تجربی به‌منظور بارزسازی دگرسانی‌های گرمابی استفاده شده است. منطقه مورد مطالعه، ربع شمال‌شرقی برگه زمین‌شناسی پاریز را که حاوی کانسارهای مس متعددی است در بر می‌گیرد. دگرسانی‌های گرمابی بارز شده با این روش شامل دگرسانی گرمابی غنی از سیلیس، دگرسانی پروپلیتیک، دگرسانی آرژلیک و دگرسانی فیلیک هستند. با استفاده از این روش، انواع مختلف دگرسانی گرمابی (آرژلیک و فیلیک) را در مناطق منطبق با محدوده‌های معدنی سرچشمه و دره زار با توجه به مشاهدات صحرایی و نمونه‌برداری‌های انجام شده تائید می‌کند. دگرسانی آرژلیک بیشتر در محدوده کانسار سریدون و به شکل محدودی در محدوده کانسارهای سرچشمه و دره زار رخنمون دارد. در این مطالعه، تفکیک دگرسانی پروپلیتیک بین کانی کلسیت و کانی‌های اپیدوت- کلریت با توجه به الگوریتم اپراتورهای منطقی نقشه‌برداری شده‌اند. نتایج نمونه برداری و مشاهدات صحرایی نیز نقشه‌های دگرسانی را تائید کرده‌اند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Enhancement of Hydrothermal Alteration in ASTER Images of Sar Cheshmeh Area, Using Logical Operators

نویسندگان [English]

  • iman maasoumi 1
  • Hojatollah Ranjbar 2
چکیده [English]

Summary
Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data and Interactive Data Language (IDL) logical operator algorithms with calculating threshold based on the land, and experimental laboratory analysis, were used to map hydrothermally altered rocks in the Sar Cheshmeh, Darrehzar, Nowchoon, Seridune and Sarkuh areas. Hydrothermal alteration enhanced by this method include silicic (hydrous quartz, chalcedony, opal), propylitic (calcite and epidote- chlorite), argillic (alunite-pyrophyllite-kaolinite) and phyllic (sericite-illite). By use of this method, different types of hydrothermal alteration in and around mineral deposits such as Sar Cheshmeh and Darrehzar, based on field observations and sampling, confirmed. Calcite and epidote- chlorite minerals were separated in the propylitic zone based on the logical operator algorithms.
Introduction
Band ratios are based on the absorption and reflection parts of the electromagnetic spectra of minerals. In order to minimize the interferences from other sources such as vegetation cover, combined use of band ratios are suggested by different workers. Logical operators suggested by Mars and Rowan (2006) and Mars (2013) are used here for mapping different minerals associated with hydrothermal alterations. The important point in using these logical operators is the proper selections of the threshold for each alteration type. This point is discussed in this paper.
 
Methodology and Approaches
 
ASTER data used for hydrothermal alteration mapping using the combined band ratio method. The combination of different band ratios with specified thresholds, is used to map hydrothermally altered areas. The threshold values are calculated based on both statistical method and field/laboratory observations. Finally, logical operators suggested by Mars and Rowan (2006) and Mars (2013) used for this purpose. The result will be a binary image based on true (presence of alteration, which is one) or false (absence of alteration, which is zero) for each pixel of the image. The alteration maps obtained are evaluated using field and laboratory observations.
 
Results and Conclusions
By use of this method, different types of hydrothermal alteration in and around mineral deposits such as Sar Cheshmeh and Darrehzar, based on field sampling/laboratory observations, confirmed. In areas such as Seridune due to the weathering of host rocks, phyllic and argillic alterations are observed together. Calcite and epidote- chlorite minerals were separated in the propylitic zone based on the logical operator algorithms. Sampling results and field observations have confirmed the alteration maps.

کلیدواژه‌ها [English]

  • ASTER
  • Logical operator
  • Hydrothermal alteration
  • Sarcheshmeh
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