Remote sensing based approach for mapping of CO_2 sequestered regions in Samail ophiolite massifs of the Sultanate of Oman

摘要

Documentation of chemical weathering and CO_2 sequestration in the Samail ophiolite massifs of the Sultanate of Oman represents an important case study for Geological Carbon Capture and Storage System (GCCSS). The present research study demonstrates the capability of remote sensing technique for mapping of weathered zones and potential CO_2 sequestration area abundances at different scales within peridotites in the northern mountain region of the Samail ophiolite massifs. The carbonate mineral index (CI) applied with other mineral indices to the TIR wavelength region of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) TIR spectral bands 13 and 14 mapped CO_2 sequesteredminerals along the structural-andwadi-controlled CO_2 flowing regions. Peridotites, the source rocks of CO_2 sequestration in the study area, were mapped using an ASTER 8, 3 and 1 band combinations. The decorrelated Landsat TM image discriminated the rock types associated with peridotites of ophiolite sequences and delineated the region of weathered and altered serpentinized peridotites in the zone of CO_2 sequestration. CO_2 sequestration mapping was carried out using Landsat TM satellite data that span 20 years (1986, 1998, 2000, 2003 and 2006) to assess the present status of CO_2 sequestration in this region. The image interpretations are verified with existing geological maps and through field and laboratory studies. The spectralmeasurements of carbonate minerals at 1300 to 2500 nmwith the spectral resolution of ~7 nmusing a PIMA SP infrared spectrometer in the field and laboratory showthe presence of hydroxyl-bearingminerals and carbonates that have spectral absorption features around 1.4 μm, 1.9 μm and 2.35 μm. The strong absorptions around 2.35 μm are mainly due to CO bonds in carbonate minerals such as calcite (CaCO_3), dolomite (CaMg(CO_3)_2), magnesite (MgCO_3), aragonite (CaCO_3) and siderite (FeCO_3), which form 15 to 57%, 12 to 53%, 9 to 38%, 11 to 21% and 3 to 8% respectively in the samples. The absorptions around 1.4 μmand 1.9 μmare caused by hydration effects of hydroxyl minerals including antigorite andmontmorillonite present at 10 to 21% and 37 to 81% respectively in the samples. The alterations of serpentinite are evidenced by the presence of antigorite and lizardite minerals. X-ray powder diffraction analyses further confirms the occurrence of CO_2 sequestered major carbonate minerals such as aragonite, calcite and dolomite in the samples. The study demonstrates that the ASTER and Landsat TM satellite multispectral sensors are useful to detect the carbonate minerals, to delineate the peridotites and to discriminate the areal abundance of potential CO_2 sequestration. This technique is a useful tool to map and monitor the region of CO_2 sequestration in well exposed arid and semi-arid regions and to analyze and understand this aspect of the world geological carbon capture and storage system.