KARAKTERISTIK PETROGRAFI DAN GEOKIMIA BATUAN GRANITOID DI PULAU BELITUNG, PROVINSI BANGKA BELITUNG
SRI ENDARTI, Dr.Eng. Ir. Lucas Donny Setijadji, S.T., M.Sc., IPU.; Dr.rer.nat. Ir. I Wayan Warmada, IPM.
2024 | Skripsi | TEKNIK GEOLOGI
Batuan granitoid
di Pulau Belitung
memiliki persebaran yang luas dan terdistribusi
secara tersebar. Batuan granit biotit ditemukan di wilayah barat, utara, dan
timur Pulau Belitung, sementara granodiorit berada di bagian timur,
dan monzonit kuarsa ditemukan di bagian selatan.
Penelitian ini mengkaji karakteristik petrografi dan geokimia batuan granitoid
tersebut. Analisis petrografi menunjukkan bahwa granitoid di Pulau Belitung
memiliki ukuran butir sedang hingga kasar, tekstur holokristalin, dan
granularitas equigranular faneritik dengan tekstur hipidiomorfik granular. Tekstur
khusus yang diamati meliputi grafik, poikilitik, dan zoning. Berdasarkan komposisinya, batuan
granitoid kaya akan biotit dan bebas hornblenda merupakan granit biotit, sedangkan
batuan yang kaya akan hornblenda dan mineral opak
merupakan granodiorit, dan granitoid dengan komposisi kuarsa yang lebih rendah
merupakan monzonit kuarsa. Berdasarkan data geokimia, granit biotit memiliki
saturasi alumina peralumina, afinitas magma high-K
calc-alkaline – shoshonite,
batuan sumber berupa metasedimen dan terbentuk pada zona kolisi. Granodiorit
memiliki saturasi alumina metalumina – peralumina, afinitas magma high-K calc-alkaline, berasal dari
batuan beku dan terbentuk pada zona subduksi. Monzonit kuarsa memiliki saturasi
alumina metalumina – peralumina, afinitas magma high-K calc-alkaline – shoshonite, batuan sumber berupa metasedimen dan terbentuk pada zona subduksi yang
cukup kompleks. Berdasarkan karakteristik petrografi dan geokimia, batuan
granit biotit diklasifikasikan sebagai tipe S, granodiorit dan monzonit kuarsa
merupakan tipe I. Penelitian ini juga menunjukkan bahwa terdapat informasi
mengenai penamaan 'adamelit' yang tidak relevan untuk digunakan, serta peta
distribusi batuan granitoid terbaru.
Kata Kunci:
Belitung, granitoid, petrografi, geokimia
Granitoid rocks on Belitung
Island are widely distributed and occur in various locations across the island.
Biotite granite is found in the western, northern, and eastern regions
of Belitung Island,
while granodiorite is located in the eastern
part, and quartz monzonite is present in the southern region. This study
examines the petrographic and geochemical characteristics of these granitoids.
Petrographic analysis reveals that the granitoids on Belitung Island have medium
to coarse grain sizes, holocrystalline texture, and
equigranular phaneritic granularity with hypidiomorphic granular texture.
Specific textures observed include graphic, poikilitic, and zoning. Based on
their composition, the biotite-rich granitoids that are free of hornblende are
classified as biotite granite, while hornblende-opaque rich rocks are
classified as granodiorite, and granitoids with lower quartz composition are
classified as quartz monzonite. Geochemical data indicate that biotite granite
exhibits peraluminous alumina saturation, high-K calc-alkaline – shoshonite
magma affinity, the source rock is metasediment rock, and formed in collision
zones. Granodiorite shows metaluminous – peraluminous alumina saturation, high-K calc-alkaline magma affinity, the source rock is igneous rock and formed
in subduction zones. Quartz monzonite has metaluminous – peraluminous alumina
saturation, high-K calc-alkaline – shoshonite magma affinity, the source rock is metasediment rock,
and formed in a complex
zone, specifically in subduction
zones. Based on petrographic and geochemical characteristics, granite biotite
is classified as S-type, granodiorite and quartz monzonite classified as
I-type. This research also indicates
the presence of information regarding the naming of 'adamelit' that is not relevant for use and the distribution map of the latest granitoid rocks.
Keyword: Belitung, granitoids, petrography, geochemical
Kata Kunci : Belitung, granitoid, petrografi, geokimia