Bulletin of the Geological Society of Malaysia 56, December 2010, pp. 67 – 73
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Geokimia volkano lumpur Pulau-Pulau Penyu, Sandakan Sabah

Baba Musta*, Mohd Harun Abdullah & Sanudin Hj. Tahir

Sekolah Sains & Teknologi, Universiti Malaysia Sabah, 88999 Kota Kinabalu, Sabah
*Emel: babamus@ums.edu.my

Abstrak— Pulau-Pulau Penyu di Perairan Sandakan, Sabah terdiri daripada Pulau Bakkungan Kechil, Pulau Selingaan dan Pulau Gulisaan. Aspek geologi yang berpotensi menarik pelancong ialah aktiviti dan kesan volkano lumpur yang terdapat di Pulau Bakkungan Kechil dan Pulau Selingaan. Cerapan geologi menunjukkan bahagian dasar pulau ini terbina daripada endapan karang poros yang cerah. Volkano lumpur yang menerobos karang membawa lumpur bersama batuan sedimen dan gas mencorakkan landskap Pulau Bakkungan Kechil. Terdapat singkapan kecil kesan volkano lumpur diperhatikan di Pulau Selingaan. Kesemua pulau terdiri daripada sedimen Resen yang melapisi permukaannya, kecuali sebahagian kecil di kawasan selatan yang mengandungi endapan karang masif. Hasil analisis geokimia sampel di Pulau Bakkungan Kechil menunjukkan komposisi SiO₂ yang tertinggi iaitu berjulat 50.27% – 94.90%; diikuti oleh Al₂O₃ yang berjulat 1.96% hingga 17.54%. Manakala, hasil analisis di Pulau Selingaan pula menunjukkan komposisi SiO₂ berjulat 10.29% – 64.80%; diikuti oleh CaO yang berjulat 2.21% hingga 44.69%. Komposisi kimia ini yang sesuai dengan kehadiran mineral kuarza, kaolinit montmorilonit dan muskovit sebagai mineral utama dalam lumpur. Mineral yang terdapat di kawasan sedimen pantai pula didominasi oleh aragonit dan sedikit kalsit. Logam-logam surih Th, Ba, Zr, Sr dan Cr adalah unsur surih tertinggi yang dikesan dalam lumpur.

Katakunci: Volkano lumpur, lumpur volkano, geokimia, Pulau-Pulau Penyu, Sabah.

Geochemistry of mud volcanoes in Penyu Islands, Sandakan, Sabah 

Abstract— Penyu Islands or Turtles Islands are located off the coast of Sandakan, Sabah and comprises Pulau Bakkungan Kechil, Pulau Selingaan and Pulau Gulisaan. Most part of the islands are blanketed by recent sediments except for a small southern portion that is made of massive coral. Geologically, the base of the entire islands are formed by light-coloured porous coral bed. The existence of mud volcanic activity at Pulau Bakkungan Kechil and traces of mud volcano at Pulau Selingaan are among geological features with potential as tourism attraction. The mud volcano intruded the coral bed and carried along mud with sedimentary rocks and gasses, and was responsible in shaping the landscape of Pulau Bakkungan Kechil and part of Pulau Selingaan. Geochemistry analysis on samples from Pulau Bakkungan Kechil show high composition of SiO₂ followed by Al₂O₃, ranging from 50.27% to 94.90% and from 1.96 to17.54%, respectively. Meanwhile, samples from Pulau Selingaan show high SiO₂ content followed by CaO, respectively 10.29% to 64.80% and 2.21% to 44.69%. This chemical composition is in concurrence with the presence of quartz, kaolinite, montmorilonit and muscovite as major minerals. The beach sediment is dominated by aragonite and some calcite. Th, Ba, Zr, Sr dan Cr are among the highest recorded trace elements in the mud.

Keywords: Mud volcano, volcanic mud, geochemistry, Penyu Islands, Sabah.

 https://doi.org/10.7186/bgsm56201010