Ifan Prasetya, Zanuar (2015) KETERDAPATAN DOLOMIT PADA BATUGAMPING FORMASI BULU DI DESA JURANGJERU, DESA GANDU, KEC. BOGOREJO DAN DESA KAJAR, DESA TEGALDOWO, KEC. GUNEM PROPINSI JAWA TENGAH. Masters thesis, U.
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Abstract
Lokasi penelitian berada di sekitar Desa Kajar, Desa Tegaldowo, Kecamatan
Gunem, Kabupaten Rembang dan Desa Jurangjero, Desa Gandu Kecamatan
Bogorejo, Kabupaten Blora. Wilayah ini memiliki potensi sebagai bahan baku
industri semen yaitu batugamping, sehingga perlu diketahui kualitasnya. Salah satu
faktor yang menentukan kualitasnya yaitu kandungan unsur MgO atau dolomit.
Dalam industri semen, kandungan unsur MgO pada batugamping mempunyai
spesifikasi kurang dari 5%. Oleh karena itu, dengan mengetahui penyebaran dolomit
diharapkan bisa memberikan penjelasan mengenai kualitasnya sehingga bisa sebagai
bahan pertimbangan untuk melakukan proses produksi penambangan batugamping.
Kondisi geomorfologi di daerah penelitian terdiri dari dua bentuk lahan yaitu
bentuk lahan karst antiklin sinklin dan perbukitan karst zona sesar dengan pola
pengaliran dendritik dan jenis sungai periodik. Terdiri dari Formasi Bulu yang
tersusun oleh batugamping berlapis, bersisipan batupasir dan batulempung yang
berumur Miosen Tengah dan Formasi Paciran yang tersusun oleh batugamping
terumbu masif berumur Pliosen Awal-Plistosen, sehingga hubungan kedua Formasi
tersebut merupakan ketidakselarasan. Struktur geologi yang dijumpai berupa kekar
dengan arah umum baratdaya-timurlaut dan tenggara-baratlaut. Terdapat 6 sesar
mendatar yang relatif berarah umum barat-timur, baratdaya-timurlaut, dan tenggarabaratlaut.
Lipatan terdiri dari sinklin dengan arah umum tenggara-baratlaut dan
baratdaya-timurlaut serta antiklin dengan arah umum tenggara-baratlaut.
Conto batugamping permukaan dilakukan analisa kimia sebanyak 92 dengan
hasil 48 conto mengandung MgO lebih dari 4,6%. Wilayah penyebaran dolomit di
Desa Tegaldowo mempunyai luas 67,5 ha dengan rata-rata MgO 15,69%.
Penyebaran disekitar Desa Jurangjeru mempunyai luas 36,7 ha dengan rata-rata MgO
17,77%. Selanjutnya di Desa Gandu mempunyai luas 12,9 ha dengan rata-rata MgO
16,26%. Terakhir di sekitar Desa Kajar mempunyai luas 12,8 ha dengan rata-rata
MgO 19%. Berdasar pengamatan sayatan tipis diperoleh nama dolostone, dolomitic
limestone, recrystallized limestone dan limestone. Proses terbentuknya dolomit pada
daerah penelitian akibat adanya percampuran antara air laut dan air tawar (mixingzone)
pada zona freatik. Apabila diaplikasikan berdasarkan arah percampuran air laut
dan air tawar, maka penyebarannya cenderung merata dibagian kiri dan kanan serta
bagian tengah hanya sedikit. Tahap dolomotisasi pada awalnya me-replace lime mud,
kemudian merubah komposisi bioclast. Selanjutnya ukuran kristal dolomit menjadi
lebih jelas, berukuran fine/medium yang mengisi pori ataupun di pinggir pori sebagai
cement dan bisa juga mengelilingi bioclasts, tahap terakhir kristal dolomit akan
mengisi kekar yang ada.
Location of the study were around the village of Kajar, Tegaldowo Village,
District Gunem, Rembang and Jurangjero village, sub-district village Gandu
Bogorejo, Blora. This region has potential as an industrial raw material cement is
limestone, so keep in mind the quality. One of the factors that determine the quality
of that content element MgO or dolomite. In the cement industry, the content of
MgO in the limestone elements have a specification of less than 5%. Therefore, to
determine the spread of dolomite is expected to provide an explanation of its quality
so that it can as consideration for limestone mining production process.
Geomorphological conditions in the study area consists of two forms, namely
land anticline syncline karst landforms and karst hills fault zone with dendritic
drainage patterns and the type of periodic river. Consisting of Bulu Formation
composed of layered limestone, sandstone and mudstone have an insert that Middle
Miocene and Paciran Formation composed by old massive reef limestones Early
Pliocene-Pleistocene, so that relations between the two formations is an
unconformity. Geological structures found in the form of a stocky with a general
direction southwest-northeast and southeast-northwest. There are 6 fault leveled
relatively common east-west trending, southwestern-northeastern, northwestern and
southeastern. Folds consists of a syncline with general direction southeast-northwest
and southwest-northeast and anticline with the general direction southeast-northwest.
Sample limestone surface as many as 92 chemical analysis with the results of
48 samples containing more than 4.6% MgO. Dolomite deployment region in the
village has an area of 67.5 ha Tegaldowo with an average of 15.69% MgO. The
spread around the village has an area of 36.7 ha Jurangjeru with an average of
17.77% MgO. Furthermore, in the village Gandu has an area of 12.9 ha with an
average of 16.26% MgO. Kajar last around the village has an area of 12.8 ha with an
average of 19% MgO. Based on the observation of thin section obtained the name of
dolostone, dolomitic limestone, recrystallized limestone and limestone. The process
of formation of dolomite in the area of research due to the mixture of seawater and
freshwater (mixing-zone) in the phreatic zone. If the mixture is applied based on the
direction of seawater and freshwater, then spread evenly on the left and tend to be
right and the middle just a little. Dolomotisasi stage initially to replace the lime mud,
and then change the composition bioclast. Furthermore, the size of crystalline
dolomite becomes more evident, measuring fine/medium that fills the pores or at the
edge of the pore as cement and can also surround bioclasts, the last stage of dolomite
crystals will fill the existing stocky.
| Item Type: | Thesis (Masters) |
|---|---|
| Divisions: | x. Faculty of Engineering, Science and Mathematics > School of Engineering Sciences |
| Depositing User: | Erny Azyanti |
| Date Deposited: | 19 May 2016 02:32 |
| Last Modified: | 19 May 2016 02:32 |
| URI: | http://eprints.upnyk.ac.id/id/eprint/1611 |
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