Karakterisasi Endapan Bauksit Laterit di Kabupaten Kotawaringin Timur, Kalimantan Tengah
DOI:
https://doi.org/10.29313/bcsme.v6i2.24293Keywords:
bauxite laterite, petrography, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), East Kotawaringin, Central Kalimantan, bauksit laterit, Kotawaringin Timur, petrografiAbstract
Abstract. Bauxite is a strategic mineral commodity that serves as the primary raw material for the aluminum industry. Kotawaringin Timur Regency, Central Kalimantan Province, has geological conditions and a humid tropical climate favorable to bauxite formation through lateritization, yet scientific studies on the characteristics of bauxite deposits in this region remain limited. This study aims to identify the bedrock, the mineralogical and geochemical characteristics, the laterite profile, and the bauxite deposit type in the Cempaga Hulu Block, Kotawaringin Timur Regency. A total of 49 observation points were sampled using hand auger, test pit, and outcrop methods, and analyzed through petrography, XRD, and XRF. The degree of weathering was evaluated using the SiO2-Al2O3-Fe2O3 ternary diagram, while the deposit type was classified following Freyssinet PH et al.,(2005). Petrographic analysis shows the bedrock to be a volcanic breccia that has undergone intense weathering, marked by relict plagioclase and pyroxene. XRD identified gibbsite and kaolinite as the dominant minerals, accompanied by hematite, goethite, quartz, and montmorillonite. Most samples plot within the strong-lateritization field, reflecting intensive silica leaching. The laterite profile consists of a topsoil horizon overlying a bauxite horizon. Integration of all datasets indicates that the deposit is best classified as an orthobauxite, formed in situ through intensive lateritization of a volcanic parent rock, with residual enrichment of aluminum controlled by gentle-to-moderate topography and well-developed drainage.
Abstrak. Bauksit merupakan komoditas mineral strategis yang menjadi bahan baku utama industri aluminium. Kabupaten Kotawaringin Timur, Provinsi Kalimantan Tengah, memiliki kondisi geologi dan iklim tropis basah yang mendukung pembentukan endapan bauksit melalui proses lateritisasi, namun kajian ilmiah mengenai karakteristik endapan bauksit di wilayah ini masih sangat terbatas. Penelitian ini bertujuan mengidentifikasi batuan dasar, karakteristik mineralogi dan geokimia, profil laterit, serta tipe endapan bauksit di Blok Cempaga Hulu, Kabupaten Kotawaringin Timur. Sebanyak 49 titik pengamatan disampling menggunakan metode hand auger, test pit, dan outcrop, kemudian dianalisis melalui petrografi, XRD, dan XRF. Tingkat pelapukan dievaluasi menggunakan diagram ternary SiO2-Al2O3-Fe2O3, sedangkan tipe endapan diklasifikasikan berdasarkan Freyssinet PH et al., (2005). Hasil analisis petrografi menunjukkan batuan dasar berupa breksi vulkanik yang telah mengalami pelapukan intensif, dicirikan oleh sisa mineral plagioklas dan piroksen. Analisis XRD mengidentifikasi gibbsite dan kaolinit sebagai mineral dominan, disertai hematit, goetit, kuarsa, dan montmorilonit. Sebagian besar sampel terdistribusi pada zona strong lateritization, yang mencerminkan pelindian silika yang intensif. Profil laterit tersusun atas horizon top soil di atas horizon bauksit. Integrasi seluruh data menunjukkan bahwa endapan bauksit di daerah penelitian diklasifikasikan sebagai orthobauxite, yaitu endapan residu yang terbentuk secara in situ melalui lateritisasi intensif pada batuan induk vulkanik, dengan pengayaan aluminium yang dikontrol oleh topografi landai hingga sedang dan sistem drainase yang baik.
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