DAFTAR ISI
SARI ..............................................................................................................
v
ABSTRACT ..................................................................................................
vi
KATA PENGANTAR ..................................................................................
vii
DAFTAR ISI .................................................................................................
x
DAFTAR GAMBAR ....................................................................................
xiv
DAFTAR TABEL ......................................................................................... xvii DAFTAR LAMPIRAN ................................................................................ xviii
BAB I PENDAHULUAN ............................................................................. 1.1
Latar Belakang ..........................................................................
1
1.2
Identifikasi Masalah ..................................................................
2
1.3
Batasan Masalah .......................................................................
3
1.4
Maksud dan Tujuan Penelitian .................................................
3
1.5
Waktu dan Lokasi Daerah Penelitian .......................................
4
1.6
Manfaat Penelitian ...................................................................
5
BAB II TINJAUAN PUSTAKA .................................................................. 2.1
6
Fisiografi Regional ...............................................................
6
2.1.1 Mandala Halmahera Timur ...................................................
6
2.1.2 Mandala Halmahera Barat ....................................................
7
2.1.3 Busur Kepulauan Gunungapi Kuarter ..................................
7
2.2
Stratigrafi Regional ..............................................................
8
2.3
Tektonik dan Struktur Geologi Regional .............................
11
x
1
2.4
Teori Dasar ..........................................................................
14
2.4.1 Batuan ultrabasa dan batuan ultramafik ..............................
14
2.4.2 Batuan ultramafik ................................................................
15
2.4.3 Kondisi pembentukan batuan di kerak bumi .......................
21
2.4.4 Ofiolit ...................................................................................
23
2.4.5 Laterit nikel ..........................................................................
26
2.5
Distribusi Laterit Nikel di Pulau Pakal ................................
35
BAB III METODE PENELITIAN ............................................................
37
3.1
Objek Penelitian ..................................................................
37
3.2
Alat-Alat yang Digunakan ..................................................
37
3.2.1 Peralatan lapangan ..............................................................
37
3.2.2 Peralatan laboratorium ........................................................
38
3.3
Tahap Persiapan ..................................................................
39
3.4
Tahap Penyelidikan Lapangan .............................................
40
3.4.1 Metode grab sampling lokasi MBT ....................................
40
3.4.2 Pengumpulan data logging bor Pakal rechecking ................
41
3.4.3 Metode selective sampling ..................................................
42
3.5
Tahap Penelitian Laboratorium ...........................................
42
3.5.1 Analisis petrografi ...............................................................
42
3.5.2 Analisis mineragrafi ............................................................
43
3.5.3 Analisis mineralogi butir .....................................................
44
3.5.4 Analisis X-Ray Diffraction (XRD) ......................................
46
3.6
Analisis Data .......................................................................
47
3.6.1 Analisis data stratigrafi dan struktur geologi ......................
47
xi
3.7
Tahap Interpretasi Data .......................................................
48
3.8
Tahap Penyusunan Laporan ................................................
49
BAB IV HASIL PENELITIAN ..................................................................
51
4.1
Geologi Pulau Pakal .......................................................
51
4.1.1
Dunit ................................................................................
52
4.1.2
Harzburgit ........................................................................
54
4.1.3
Aluvium ...........................................................................
56
4.2
Karakteristik Batuan Ultramafik ....................................
60
4.2.1
Dunit ...............................................................................
62
4.2.1.1
Distribusi batuan dan kenampakan lapangan ..................
62
4.2.1.2
Deskripsi mikroskopik .....................................................
63
4.2.1.3
Identifikasi mineralogi butir ...........................................
67
4.2.1.4
Analisis XRD ..................................................................
69
4.2.1.5
Analisis kimia ..................................................................
70
4.2.1.6
Interpretasi paragenesa batuan ........................................
73
4.2.2
Harzburgit .......................................................................
76
4.2.2.1
Distribusi batuan dan kenampakan lapangan ..................
76
4.2.2.2
Deskripsi mikroskopik .....................................................
77
4.2.2.3
Analisis XRD ..................................................................
81
4.2.2.4
Analisis kimia ..................................................................
81
4.2.2.5
Interpretasi paragenesa batuan ........................................
83
4.2.3
Serpentinit ......................................................................
87
4.2.3.1
Distribusi batuan dan kenampakan lapangan .................
87
4.2.3.2
Deskripsi mikroskopik .....................................................
87
xii
4.2.3.3
Analisis XRD ..................................................................
89
4.2.3.4
Interpretasi paragenesa batuan ........................................
90
4.2.4
Olivin gabro ....................................................................
92
4.2.4.1
Distribusi batuan dan kenampakan lapangan .................
92
4.2.4.2
Deskripsi mikroskopik .....................................................
93
4.2.4.3
Analisis XRD ...................................................................
94
4.2.3.4
Interpretasi paragenesa batuan ........................................
94
4.3
Laterit Nikel Pulau Pakal .................................................
98
4.3.1
Karakteristik laterit nikel ................................................
99
4.3.1.1
Overburden .....................................................................
99
4.3.1.2
Limonit .........................................................................
100
4.3.1.3
Saprolit .........................................................................
100
4.3.1.4
Bedrock .........................................................................
102
4.3.2
Karakteristik precursor laterit nikel ..............................
103
4.3.3
Keterdapatan laterit nikel ..............................................
105
BAB V KESIMPULAN .............................................................................
107
DAFTAR PUSTAKA .................................................................................
109
LAMPIRAN
xiii
DAFTAR GAMBAR
Gambar 1.1
Distribusi Endapan Bijih Laterit Nikel Indonesia (PT. INCO dalam Ahmad, 2006) ..........................................
2
Gambar 1.2
Lokasi Daerah Penelitian ........................................................
5
Gambar 2.1
Fisiografi Pulau Halmahera (Apandi dan Sudana, 1980) .......
7
Gambar 2.2
Peta Geologi Regional Daerah Sangaji-MoronopoTanjung Buli dan Pulau Pakal (Modifikasi sebagian lembar peta Geologi Regional Ternate, Maluku Utara, Apandi dan Sudana, 1980) .....................................................
10
Gambar 2.3
Distribusi Ofiolit di Seluruh Dunia (Kadarusman, 2001) ......
12
Gambar 2.4
Distribusi Ofiolit di Asia Tenggara (Kadarusman, 2001) .......
12
Gambar 2.5
Peta Tektonik Regional Halmahera (lihat pada bagian A); bagian B merupakan penampang geologi molucca sea plate yang menunjukkan adanya double arc system/ molucca sea collision zone; bagian C merupakan profil pada lengan bagian selatan Halmahera (Hamilton, 1979) ...... 13
Gambar 2.6
Diagram fasa olivin tholeitik, mengacu pada kondisi tekanan dan temperatur (modifikasi setelah Green dan Ringwood dalam Jacob, 2004) ........................................
16
Gambar 2.7
Diagram gradien panas di kerak bumi (Ahmad, 2006) ..........
22
Gambar 2.8
Skema Penampang Subduksi-Obduksi Ofiolit (Coleman, 1981) ....................................................................
23
Kolom kesebandingan a) ofiolit tipe Harzburgit dan b) ofiolit tipe Lerzolit (Boudier dan Nicolas, 1989) .............
24
Gambar 2.10 Profil laterit nikel (Ahmad, 2005) ..........................................
31
Gambar 2.11 Variasi profil laterit disebabkan oleh iklim dan topografi (PT. INCO dalam Ahmad, 2006) ...........................
35
Gambar 2.12 Distribusi laterit nikel di Pulau Pakal (Tim eksporasi antam unit geomin Buli, 2011) ..............................
36
Gambar 2.9
xiv
Gambar 3.1
Peta lokasi Mining Block Test (MBT) ....................................
41
Gambar 3.2
Diagram Klasifikasi untuk Variasi Batuan Mafik dan Ultramafik (Streckeisen, 1974) .......................................
43
Mikroskop Polarisator Tipe Olympus DP12 untuk analisis petrografi dan mineragrafi milik PT. ANTAM.Tbk Unit Geomin .............................................
44
Mikroskop Stereobinokuler Tipe Nikon SMZ800 milik PT. ANTAM.Tbk Unit Geomin ....................................
45
Difraktometer Tipe Bruker D8 Advance milik PT. ANTAM.Tbk Unit Geomin .............................................
46
Gambar 3.6
Ilustrasi makna rezim tekanan (Delvaux et al., 1997) ............
48
Gambar 3.7
Bagan Alir Penelitian .............................................................
50
Gambar 4.1
Lokasi pengambilan conto batuan ultramafik ........................
52
Gambar 4.2
Analisis data kekar dan diagram rosette di Pulau Pakal .........................................................................
55
Gambar 4.3
Peta Geomorfologi Pulau Pakal ..............................................
57
Gambar 4.4
Peta Geologi Struktur Pulau Pakal .........................................
58
Gambar 4.5
Peta Geologi Pulau Pakal .......................................................
59
Gambar 4.6
Singkapan dunit di lapangan ..................................................
63
Gambar 4.7
Foto mineralogi butir tiga conto soil di lokasi MBT .............
69
Gambar 4.8
Lokasi titik bor pada peta Mining Block Test (MBT) hasil pengukuran lapangan ........................................
71
Profil analisis kimia titik bor DH/PKL-7 pada bedrock dunit .................................................................
72
Gambar 3.3
Gambar 3.4
Gambar 3.5
Gambar 4.9
Gambar 4.10 Diagram pembentukan dunit .................................................
74
Gambar 4.11 Fotomikro sayatan tipis dan sayatan poles dunit ...................
75
Gambar 4.12 Singkapan harzburgit di lapangan .........................................
77
Gambar 4.13 Peta lokasi titik bor Pakal rechecking ...................................
82
xv
Gambar 4.14 Profil analisis kimia titik bor DH/PKL-10 pada bedrock harzburgit ........................................................
83
Gambar 4.15 Diagram pembentukan harzburgit .........................................
85
Gambar 4.16 Fotomikro sayatan tipis dan sayatan poles harzburgit ..........
86
Gambar 4.17 Singkapan serpentinit di lapangan .........................................
87
Gambar 4.18 Diagram pembentukan serpentinit berdasarkan diagram gradien panas kerak bumi (Ahmad, 2006) ..............
91
Gambar 4.19 Fotomikro sayatan tipis dan sayatan poles serpentinit ..........
91
Gambar 4.20 Singkapan olivin gabro pada PT-12A di lapangan ................
92
Gambar 4.21 Diagram pembentukan olivin gabro ......................................
95
Gambar 4.22 Fotomikro sayatan tipis dan sayatan poles sampel PT-12A ......................................................................
96
Gambar 4.23 Kolom kesebandingan a) ofiolit tipe Harzburgit dan b) ofiolit tipe Lerzolit (Boudier dan Nicolas, 1989), litologi batuan ultramafik di Pulau Pakal terletak di bagian bawah seri ofiolit tipe Harzburgit ...............................
97
Gambar 4.24 Kenampakan lapangan lokasi MBT .......................................
98
Gambar 4.25 Kenampakan lapangan dinding laterit nikel di sebelah barat lokasi MBT ......................................................
99
Gambar 4.26 Kenampakan lapangan mineral garnierit dan krisopras ..........................................................................
92
Gambar 4.27 Kenampakan lapangan bedrock di sekitar lokasi MBT .........
94
Gambar 4.28 Interpretasi profil analisis kimia laterit nikel dari precursor yang berbeda ......................................................... 104
xvi
DAFTAR TABEL
Tabel 2.1
Kolom stratigrafi regional Halmahera bagian Timur (Hall et al., 1991) .......................................................
9
Tabel 2.2
Batuan ultramafik dan ultrabasa (Ahmad, 2006) ..................
15
Tabel 2.3
Kandungan nikel pada mineral olivin, piroksen, dan kromit (Ahmad, 2006) ....................................................
21
Perbandingan antara tipe ofiolit harzburgit dan tipe ofiolit lerzolit (Nicolas, 1989) ........................................
25
Mineral-mineral yang berasosiasi dengan laterit nikel dan batuan ultramafik (Ahmad, 2006) ..........................
34
Daftar pengukuran dan jumlah individu kekar tiap stasiun .............................................................................
54
Daftar contoh batuan di Pulau Pakal yang digunakan untuk studi ...........................................................
60
Jumlah conto batuan berdasarkan jenis batuan ultramafik ...................................................................
62
Tabel 4.4
Persentase komposisi mineral dunit dari conto batuan ..........
64
Tabel 4.5
Derajat serpentinisasi dunit ....................................................
64
Tabel 4.6
Daftar hasil analisis mineralogi butir semi kuantitatif berdasarkan fraksi .................................................
68
Persentase kandungan mineral pada dunit hasil analisis XRD ..........................................................................
70
Tabel 4.8
Diagram interpretasi paragenesa dunit ...................................
73
Tabel 4.9
Persentase komposisi mineral harzburgit dari conto batuan ...........................................................................
77
Tabel 4.10
Derajat serpentinisasi harzburgit ............................................
78
Tabel 4.11
Persentase kandungan mineral pada harzburgit hasil analisis XRD ..................................................................
81
Tabel 2.4
Tabel 2.5
Tabel 4.1
Tabel 4.2
Tabel 4.3
Tabel 4.7
xvii
Tabel 4.12
Diagram interpretasi paragenesa harzburgit ...........................
84
Tabel 4.13
Persentase komposisi mineral serpentinit dari conto batuan ...........................................................................
88
Tabel 4.14
Diagram interpretasi paragenesa serpentinit ...........................
90
Tabel 4.15
Diagram interpretasi paragenesa olivin gabro ........................
94
DAFTAR LAMPIRAN
Lampiran I Deskripsi Petrografi dan Mineragrafi Lampiran II Deskripsi Mineralogi Butir Lampiran III Analisis Sinar-X Difraksi Lampiran IV Analisis Kimia
xviii
