GUNUNG BADAK, CIKEPUH-CITISUK, DAN CITIREM, KOMPLEKS PETROTEKTONIK JALUR SUBDUKSI KAPUR JAWA BARAT

Share this post :

SARI
Kompleks Gunung Badak, Kompleks Cikepuh-Citisuk, dan Kompleks Citirem berada di
Teluk Ciletuh, merupakan lokasi dari kumpulan batuan Pra-Tersier. Daerah Teluk
Ciletuh berada di Kabupaten Sukabumi, Provinsi Jawa Barat. Batuan Pra-Tersier di
Ciletuh dikenal luas sebagai tektonik melange yang terbentuk dari penujaman lempeng
Indo-Australia terhadap Eurasia selama kala Kapur- Paleosen.
Ini merupakan studi menyeluruh dari kumpulan petrotektonik melalui perangkuman dan
analisis penelitian terdahulu (peta geologi dan studi laporan tidak terbit). Data diperoleh
melalui pemetaan geologi detil skala 1: 100.000, pengamatan lapangan, analisis
petrografi, analisis geokimia (dengan peralatan JEOL superprobe 733), analisis kimia
mineral dan pengukuran tekanan dan temperatur.
Kompleks Gunung Badak terdiri dari ofiolit (peridotit, gabro dan lava basal), batuan
metamorfik (serpentinit, kuarsit, filit, dan sekis), Kompleks Cikepuh-Citisuk disusun
batuan beku basa, ultrabasa, dan metamorfik sebagai lava basal, gabro, peridotit, dan
sekis, Kompleks Citirem disusun oleh lava basal (struktur bantal dan vesikuler).
Ke arah selatan (Gunung Badak menuju Citirem), kompleks ini disusun oleh kerak
samudera bagian atas; sebaliknya ke utara Kompleks Ciletuh disusun oleh kerak
samudera bagian dalam. Tersingkapnya batuan-batuan Pra-Tersier akibat adanya
pengurangan kecepatan penekukan pada masa Eosen-Oligosen Bawah, diimbangi
terbentuknya akresi, sehingga hadirnya kompleks melange yang mengandung blokblok
batuan ultramafik dan terdiri dari lempeng-lempeng serpentinit dan lava bantal. Di
saat bersamaan terjadi obduksi yang menyebabkan proses metamorfisme; pada kala
Oligosen Atas, adanya penambahan penekukan yang menyebabkan batuan metamorf
mengalami retrograde metamorfism, ditunjukkan dengan hadirnya mineral klorit yang
menggantikan aktinolit, albit dan kelompok epidot menggantikan plagioklas pada
batuan epidot amfibolit.
Kata kunci : Petrotektonik, Ciletuh, Melange, Penunjaman, Gunung Badak.

ABSTRACT
Gunung Badak, Cikepuh-Citusuk and Citirem Complex is situated in Ciletuh Bay. This
location consist of Pre-Tertiary rocks assemblages. Ciletuh Bay region located in
Sukabumi Regency, in West Java Province. The Pre-Tertiary rocks at Ciletuh have
been widely considered as tectonic mélange, which occured by subduction of Indo-
Australian and Eurasian plate during Cretaceous - Paleocene time.
This is a comprehensive study of petrotectonic assemblages by the results of
summary and analysis of previous research (geological map and unpublished reports).
Primary data are obtained from detailed geological mapping on 1: 100000 scale, field
observations and petrographic analysis, geochemical analysis (with JEOL superprobe
733), mineral chemical analysis, and temperature and stress measurement.
Gunung Badak Complex consists of ophiolite (peridotite, gabbro, and pillowed basalt),
metamorphic (serpentinite, quartzite, phyllite, and schist), and sedimentary rocks
(greywackes, nummulites limestone, black shale, red clay, and polymic breccias).
Cikepuh-Citisuk Complex consists of basic, ultrabasic and metamorphic rocks as
basaltic lava, gabbro, peridotite, and schist. Citirem Complex consists of thoelitic
basaltic lava (pillowed and vesiculars).
In southernward (Gunung Badak to Citirem), this complex consists of upper part
Oceanic Crust, inversely northward the Ciletuh Area consist inner part Oceanic Crust.
Uplifting of pre-Tertiary rocks is due to less of speed in underside Eosen-Oligosen
times, in balance by created of accretion, during the present of melange complex that
implied blocks of ultramafic rocks and consists of sepernitite plates basaltic lava. In the
same time obduction that made metamorphic process, at Upper Oligosen period, the
increase of subduction which cause metamorf rocks to go through metamorphism
retrogrades, showing by attended of klorite mineral that replaced aktinolit, albit and
epidot groups replaced amfibolit epidot rocks.
Keywords: Petrotectonic, Ciletuh, Melange, Subduction, Gunung Badak.

 

By

Yoal Dianto dan1 Yudih Saamena1
1Fakultas Teknik Geologi, Universitas Padjadjaran,
Jl. Raya Bandung Sumedang KM.21 Jatinangor 45363 Telp./Fax (022) 7796545.
Email : yoal.dianto@yahoo.co.uk, yudih.saamena@yahoo.com

»»  read more

Introduction geology

From Wikipedia, the free encyclopedia

Geology (from Greek: γη, gê, "earth"; and λόγος, logos, "speech" lit. to talk about the earth) is the science and study of the solid matter that constitutes the Earth. Encompassing such things as rocks, soil, and gemstones, geology studies the composition, structure, physical properties, history, and the processes that shape Earth's components. It is one of the Earth sciences. Geologists have established the age of the Earth at about 4.6 billion (4.6x10⁹) years, and have determined that the Earth's lithosphere, which includes the crust, is fragmented into tectonic plates that move over a rheic upper mantle (asthenosphere) via processes that are collectively referred to as plate tectonics. Geologists help locate and manage the Earth's natural resources, such as petroleum and coal, as well as metals such as iron, copper, and uranium. Additional economic interests include gemstones and many minerals such as asbestos, perlite, mica, phosphates, zeolites, clay, pumice, quartz, and silica, as well as elements such as sulfur, chlorine, and helium. Geology is also of great importance in the applied fields of civil engineering, soil mechanics, hydrology, environmental engineering and geohazards.

Planetary geology (sometimes known as Astrogeology) refers to the application of geologic principles to other bodies of the solar system. Specialised terms such as selenology (studies of the moon), areology (of Mars), etc., are also in use. Colloquially, geology is most often used with another noun when indicating extra-Earth bodies (e.g. "the geology of Mars").

The word "geology" was first used by Jean-André Deluc in the year 1778 and introduced as a fixed term by Horace-Bénédict de Saussure in the year 1779. The science was not included in Encyclopædia Britannica's third edition completed in 1797, but had a lengthy entry in the fourth edition completed by 1809.An older meaning of the word was first used by Richard de Bury to distinguish between earthly and theological jurisprudence.

»»  read more