Muhamad Deva Pratama Deva, Mira Meirawaty, Ramadhan Adhitama, Himmes Fitra Yuda, Meldayan Monang Anouw

GEOLOGI DAN INDIKASI MILONITIK PADA BATUAN GRANITOID DI DAERAH SANGGAU, KALIMANTAN BARAT, INDONESIA

Introduction

Geologi dan indikasi milonitik pada batuan granitoid di daerah sanggau, kalimantan barat, indonesia. Telusuri geologi dan indikasi milonitik pada batuan granitoid Mesozoikum di Sanggau, Kalimantan Barat. Penelitian mengungkap zona geser dan deformasi brittle-ductile signifikan.

Abstract

Lokasi penelitian secara administratif terletak di Kabupaten Sanggau, Kalimantan Barat, yang secara fisiografis termasuk ke dalam Blok Kalimantan Barat. Penelitian ini bertujuan untuk memetakan kondisi geologi permukaan serta mengidentifikasi indikasi deformasi pada batuan granitoid berumur Mesozoikum. Metodologi yang diterapkan mencakup pemetaan lapangan, analisis geomorfologi, serta analisis struktur makro dan mikro (petrografi). Hasil penelitian menunjukkan bahwa daerah penelitian terdiri dari tiga satuan geomorfologi utama, yaitu Satuan Perbukitan Intrusif, Satuan Perbukitan Sisa, dan Satuan Dataran Denudasional. Stratigrafi regional di daerah penelitian tersusun atas Unit Metamorf Filitik (Paleozoikum), Unit Granitoid Formasi Embuoi (Mesozoikum), dan Unit Sedimen Tersier. Temuan utama dalam penelitian ini adalah teridentifikasinya zona geser (shear zone) yang intensif pada tubuh granitoid, yang dicirikan oleh kehadiran mikrostruktur milonit dengan tingkat deformasi rendah hingga tinggi. Hal ini mengonfirmasi adanya aktivitas deformasi brittle-ductile yang signifikan di wilayah tersebut. The research area is administratively located in Sanggau District, West Kalimantan, which physiographically belongs to the West Borneo Block. This study aims to map the geological conditions and identify indications of deformation in Mesozoic granitoid rocks. The methodology includes field mapping, geomorphological analysis, and macro and microstructural analysis. The results show that the research area consists of three main geomorphological units, there are the Plutonic Hill Unit, the Denudational Plain Unit, and the Residual Hill Unit. The stratigraphy consists of the Phyllitic Metamorphic Unit (Paleozoic), the Embuoi Formation Granitoid Unit (Mesozoic), and the Tertiary Sedimentary Unit. The main finding is the strong indication of shear zones within the granitoid body, characterized by the presence of low to high-grade mylonite microstructures. This confirms significant brittle-ductile deformation activity in the region.

Review

This paper, titled 'GEOLOGI DAN INDIKASI MILONITIK PADA BATUAN GRANITOID DI DAERAH SANGGAU, KALIMANTAN BARAT, INDONESIA,' presents a focused geological investigation in the Sanggau District, West Kalimantan, an area situated within the broader West Borneo Block. The primary objective of the research was to meticulously map the surface geological conditions and, critically, to identify and characterize indications of deformation within the Mesozoic granitoid rocks prevalent in the region. This study addresses a fundamental aspect of regional tectonics by exploring the deformational history of significant geological units in a less-explored area. The methodology employed for this research is comprehensive, integrating both field-based observations and laboratory analyses. It includes extensive field mapping to delineate the spatial distribution of geological units, complemented by geomorphological analysis to interpret the landscape evolution. Crucially, the study utilized both macro- and microstructural analysis, specifically employing petrography, to identify deformational features across various scales. The findings reveal a landscape characterized by three main geomorphological units: Plutonic Hill, Denudational Plain, and Residual Hill units. Stratigraphically, the area comprises a Paleozoic Phyllitic Metamorphic Unit, the Mesozoic Embuoi Formation Granitoid Unit, and a Tertiary Sedimentary Unit. The most significant finding, however, is the conclusive identification of intense shear zones within the granitoid body, evidenced by the pervasive presence of low to high-grade mylonite microstructures, which unequivocally confirm substantial brittle-ductile deformation activity in the region. The identification of widespread mylonitic textures and intense shear zones within the Mesozoic granitoids of Sanggau represents a significant contribution to understanding the structural evolution and tectonic history of the West Borneo Block. This finding provides critical evidence for past brittle-ductile deformation events, offering valuable insights into the regional stress regimes and crustal dynamics that shaped this part of Sundaland. Such detailed structural characterization is vital for reconstructing the geodynamic processes and serves as a strong foundation for future research into the kinematics, timing, and regional implications of these significant deformational events. The paper effectively integrates various geological techniques to provide a comprehensive picture of the area's geology and structural complexities.

Full Text

Comments

You need to be logged in to post a comment.