Kontrol Jarak antara Endapan Gambut dan Batuan Alas terhadap Distribusi Unsur Jejak pada Gambut di Taman Nasional Sebangau, Palangka Raya, Kalimantan Tengah

Auvanda Ivan Muhammad, Prof. Dr. Ir. Ferian Anggara, S.T., M.Eng., IPM., Aulia Agus Patria, S.T., M.Sc.

2026 | Skripsi | TEKNIK GEOLOGI

Penelitian ini dilakukan pada lahan gambut Taman Nasional Sebangau, Palangka Raya, Kalimantan Tengah, yang terendapkan di atas batuan alas felsik berumur Kapur Akhir. Penelitian ini bertujuan untuk mengidentifikasi karakteristik gambut dan batuan alas berdasarkan aspek petrologi, mineralogi, dan geokimia; memahami kontrol jarak antara gambut dan batuan alas terhadap distribusi vertikal dan lateral karakteristik gambut; serta mengetahui mekanisme yang mengontrol distribusi unsur jejak dan REY+Sc pada gambut. Metode yang digunakan meliputi analisis petrografi, petrografi organik, XRD, SEM-EDS, proksimat, ICP-MS, dan ICP-AES terhadap sampel gambut dan batuan alas. Hasil penelitian menunjukkan bahwa gambut didominasi oleh material organik terdegradasi yang berukuran halus di bagian tepi dan dasar endapan diikuti dengan peningkatan kadar abu, sedangkan material anorganik terdiri dari unsur jejak (CC>2) yaitu Zr dan Hf, serta REY+Sc yang hadir dalam berbagai mode keterdapatan, terutama sebagai mineral aksesori yang berikatan dengan kuarsa dan zirkon, mineral lempung seperti kaolinit, ilit, dan klorit, oksida Fe-Ti meliputi titanit, ilmenit, magnetit, anatase dan rutil, serta mineral fosfat pembawa unsur jejak seperti monazit dan xenotim. Batuan alas berupa riolit berperan sebagai sumber utama material detrital dan unsur jejak. Distribusi unsur jejak dan REY+Sc menunjukkan peningkatan konsentrasi ke arah batuan alas secara vertikal dan lateral, dengan pola kombinasi dome-shaped dan fan-shaped. Mekanisme pengayaan unsur jejak dan REY+Sc dikontrol oleh suplai sedimen detrital hasil pelapukan batuan alas (terrigenous), serta dipengaruhi oleh migrasi fluida meteorik (infiltrational) yang mendukung redistribusi unsur dalam endapan gambut. Penelitian ini menunjukkan bahwa kontrol jarak terhadap batuan alas merupakan faktor utama yang mengendalikan karakteristik dan distribusi unsur jejak pada gambut sebagai analog batubara yang terbentuk.

This study was conducted in the peatland of Sebangau National Park, Palangka Raya, Central Kalimantan, which is deposited over Late Cretaceous felsic basement rocks. The objectives of this study are to characterize peat and basement rocks based on petrological, mineralogical, and geochemical aspects; to evaluate the distance control between peat and basement rocks on the vertical and lateral distribution of peat characteristics; and to determine the mechanisms controlling the distribution of trace elements and REY+Sc in peat. The methods employed include petrographic analysis, organic petrography, XRD, SEM-EDS, proximate, ICP-MS, and ICP-AES on peat and basement rock samples. The results indicate that the peat is dominated by fine-grained degraded organic material, particularly at the margins and basal parts of the deposit, which is accompanied by an increase in ash content. The inorganic material consists of trace elements (CC>2), specifically Zr and Hf, as well as REY+Sc, which occur in various modes of occurrence. These elements are primarily associated with accessory minerals linked to quartz and zircon, clay minerals such as kaolinite, illite, and chlorite, Fe– Ti oxides including titanite, ilmenite, magnetite, anatase, and rutile, and phosphate minerals hosting trace elements such as monazite and xenotime. The basement rock, identified as rhyolite, acts as the primary source of detrital material and trace elements. The distribution of trace elements and REY+Sc shows increasing concentrations toward the basement rocks both vertically and laterally, forming a combination of dome-shaped and fan-shaped patterns. The enrichment mechanism of trace elements and REY+Sc is controlled by detrital input derived from the weathered basement rocks (terrigenous), and is further influenced by meteoric fluid migration (infiltrational), which facilitates element redistribution within the peat deposit. This study demonstrates that the distance to basement rocks is the primary control factor governing the characteristics and distribution of trace elements in peat, which serves as an analogue for the formation of coal.

Kata Kunci : Gambut, Riolit, Unsur Jejak, REY+Sc, Distribusi Vertikal dan Lateral