Badan Geologi

Pusat Survei Geologi

Regolith Landform Unit Mapping using Hyperspectral Imaging (Case study: Block G TickHill Mt.Isa, Australia)



Abstract

The advent a new hyperspectral has improved the rapid surface mapping of minerals and earth materials. This research is creating the mineral maps using Hy Map in Tick Hill Mount Isa Northwest Queensland as a guide for the regolith landform unit mapping. Tick Hill area is part of the Proterozoic Eastern and Western Fold Belt Province of Mt.Isa Inlier Complex. The areas were covered by Mesozoic and Paleozoic lithologies dominated by medium to coarse hornblende-biotite granite and gneiss intruded during 1760 - 1720 Ma. Highly weathered landform covered the whole area. The Mesozoic sediments have experienced to deep weathering currently present in the form of mesas. The weathering profiles are dominated by kaolinite, smectite, and pedogenic carbonates with some secondary silicification. Part of the landform was covered by colluvium which varied in thickness from less than 1 meter to up to 12 meter in certain places. The general image processing for Hy Map has been done for the area. In addition, ASD spectra laboratory has been applied to validate the remotely sensed mineral information. Iron Oxide and Al-OH (kaolinite, illite, smectite) mineral maps have been successfully created through HyMap imagery. Those can easily identified through the band ratio with some mask application (relative band depth method) in Hy Map. For final process, GIS method is used to overlay all the data producing regolith landform unit map. AL-OH mainly kaolinite mineral map is showing the usefulness for identification the surface regolith mapping (mottle zone) and its crystallinity maps can differentiate transported and in situ regolith materials. In addition, Iron oxide map is able to identify ferruginous and laterite surface materials.

Abstrak

Perkembangan teknik inderaan jauh hiperspektral telah mempermudah pemetaan mineralogi dan material penyusunan bumi. Tulisan ini membahas pemetaan mineralogi dengan HyMap di daerah Tick Hill Mount Isa, Northwest Queensland sebagai arahan untuk pemetaan bentang a/am regolit. Daerah Tick Hill merupakan bagian dari sabuk lipatan bagian timur dan barat dari Kompleks Mount Isa.
Batuan daerah ini tersusun oleh batuan berumur Paleozoikum - Mesozoikum yaitu granit hornlende sedang-kasar, dan gneiss yang diintrusi selama kurun waktu 1760-1720 Ma. Batuan - batuan tersebut ditutupi oleh soil. Batuan sedimen Mesozoikum telah terlapukkan cukup tebal yang membentuk bentang a/am mesa (tinggian menyerupai plateau). Tanah lapukan didominasi oleh mineral kaolin, smektit, dan karbonat pedogenik dan silisifikasi sekunder. Sebagian bentang a/am ditutupi oleh kolovium dengan ketebalan berkisar antara 1 meter sampai 12 meter. Citra HyMap dilakukan pemrosesan secara digital. Untuk validasi citra dilakukan pengukuran spektral batuan di laboratorium dengan menggunakan a/at Analytical Spectral Device (ASD). Beberapa peta mineral dihasilkan yaitu peta mineral oksida besi, peta mineral kaolinit, peta mineral ilit dan peta mineral smektit. Peta - peta tersebut dianalisis dengan metode GIS yaitu ditumpang- tindih (overlay) untuk menjadi peta bentang a/am regolit. Hasil analisis memberikan fakta bahwa peta mineral kaolinit dan perbedaan kristalinitasnya dapat membedakan tanah lapukan tertransport dan lapukan insitu. Peta mineral oksida besi dapat membedakan tanah lapukan yang bersifat ferrugineous dan endapan laterit permukaan.

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Jurnal Geologi dan Sumber Daya Mineral

Vol. 17 No. 4, November 2016

0853 - 9634

JGSM