CHARACTERISTICS OF MINERALS WITH SPECTROSKOPIC IR AT THE GOLD MINING AREA OF BOTAK MOUNTAIN

There are three rock samples that have been taken from the gold mining area of Botak mountain. The rock samples were then analyzed with spectroscopic IR to estimate the characteristic of mineral in the area. Analysis results indicate that the type of mineral found in rock samples 2 is dominated by Kaolinite, Organic Carbon, Palygorskite and Quartz. So it can be estimate the type of rock contained in that area is Quartzite. The analysis result of mineral type analysis on rock samples 1 dan 3 have similarities that is Kaolinite, Organic Carbon, Palygorskite, and Albite. So it can be estimate that the other types of rock in the area are Andesite and Limestone. The existence of Andesit and Limestone shows that there has been alteration and hydrothermal mineralization from volcanic origin rock. So it can be estimate that these rocks are the bearing rocks and hosted rocks of base metals and gold. Whereas the quartzite is a bond mineral from gold carrying rocks. Copyright © 2019, Helda Andayany. This is an open access article distributed under the creative commons attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


INTRODUCTION
Geological history explains that Buru Islands is included in the South Moluccas region which is the Banda Arc, the archipelagic system that forms an arc around the horseshoe basin of the Banda Sea that opens to the West. South Moluccas is bounded by deep bows (active volcanism) and external bows (free from volcanism) [1]. Buru Island is included in the outer Arc that has a dominated by structural mountains. Geological history also explains that the island of Buru is part of the Maluku Islands is composed of shallow sea deposits estimated to be aged Plitosen until Holocene. The composition of rocks consist of limestone, napal, and alluvium deposits. Formation of rock compilers of Buru Island region starts from the youngest of which is Formation of Tassel, Hemorrhoid Formation and Alluvium Formation. So there are variations of rocks on Buru Island, which are alluvium, limestone, corals, napal, sandstone, conglomerate, andesite and basalt tuffs. There are also filit, skist and quartzite [2].
The Botak Mountain area is located in Namlea, Buru Island. This area is a gold mining area of the people. The historical background of this region's geology strongly proves the presence of gold veins in the area. The mineral characteristics in the gold mining area are both gold-carrying minerals which are usually associated with bonded minerals and sulphide deposits that have been oxidized in the gold mining area of Botak Mountain.
The gold mining area of Botak Mountain is dominated by 3 (three) types of rocks that are interpreted related to gold mineralization. These rocks are andesite, quartzite and limestone which is undergoing alteration and is a member of the Alluvium Formation. The rocks that are most affected and serve as trap rock for the occurrence of mineralization are limestone and quartzite. For rocks that are interpreted as gold metal carriers are basaltic andesite veins.
Based on the above, this research is intended to interpret the types of minerals and rocks that experience alteration and mineralization of volcanic rocks. In addition, it can interpretation the rock that serves as a trap (hosted rocks) and gold bearer rock (gold bearing rocks). This is done by analyzing rock samples taken from the gold mining area of Botak Mountain using spectroscopic IR.

PREVIOUS STUDY
The geological structure and tectonic history of the Bald Mountain area, Buru Island is very influential on the gold formation process in this area. Stratigraphy of Buru Island [3], consisting of metamorphic rocks (filit,  [4]. The formation of gold in nature through a process of magmatism from the earth's core or the concentration of minerals to the surface, as well as the activity of the volcanic from the volcano. The gap from the volcanic activity causes high-pressure magmatic water to rise to the surface of the earth. When magmatic water in the form of steam reaches the surface of the earth comes in contact with meteoric water which causes sulphide ions and chloride ions that carry the precipitated gold. Meteoric water usually occupies the zones of frozen rock cracks that undergo alteration processes due to warming by magmatic water. As the mineral deposits increase on the cracks, the longer the cracks are closed by the accumulation of deposits from metals containing complex ions containing gold, while the mechanical concentration activity produces a placer deposit. Gold deposits are categorized into two: primary deposits which are deposits of igneous rock and gold minerals forming gold or gold veins (vein) and deposits of plates originating from golden rock deposits that have been eroded by water into streams (usually deposits The placer is present in the waterway below the hill or mountains) [5].
Gold deposits can also be formed through the process of weathering frozen rock and gold veins that can erode and remove gold minerals where gold minerals will be sedimented in very fine-grained materials, clay minerals (kaolinite) [6]. But if there is no intrusion, gold minerals could have existed in limestone.

METHODS
The sample used in this study amounted to three samples, namely 3 rock samples from the gold mining area at Botak Mountain, Buru District and then analyzed by using IR spectroscopy 3000 [7]. From the result of the sample test to threes rocks, we get the graph of transmittance spectrum (%) vs. wave number (cm −1 ), then the graph to interpreted functional group, compound, vibration type, intensity and mineral type contain in each rock sample.
Rock samples taken from the gold mining area of Botak Mountain, smoothed and then added pure KBr powder and stirred until evenly distributed. Next, the mixture is placed in the mold and pressed by means of a mechanical pressure device then the sample (KBr pellet formed) is taken and analyzed. The analysis results show that the value of the wavelengths analyzed from the absorbance and transmitance spectrum generated from the IR spectroscopic [3]. The value of wave number will be used to interpret the mineral and rock types found in the gold mining area of Gunung Botak.

RESULTS AND DISCUSSION
The result of analysis of rock samples with spectroscopic IR is shown by IR spectrum graph in   In FIG. 3, the spectrum graph is identified as a function group in different regions of the wave number. In the wavelength (3300 − 3500) cm −1 region there is a stretching function group N − H that is an amine compound. Next, there is a C − H stretching function group, there is also a function group C = C with a wave number region (1620−1680) cm −1 and a function group C − O with the wave number (1679 − 1820) cm −1 . From the graph above also shows that there are several wave numbers that are not included in the characteristic of the IR spectroscopic absorption function, there are only a few wave numbers included in the cluster of absorbent function group.
The result of IR spectrum graphic analysis for rock samples 3 shows that the function group N-H from wave number (3300 − 3500) cm −1 with spectroscopic  Based on the type of minerals obtained from the IR spectroscopic analysis, it can be interpreted by the type of rocks based on the minerals that have been analyzed. The interpreted rock types are presented in Table 4. The analysis result of mineral type on rock samples 1 and 3 have similarities that is dominated by Kaolinite, Organic Carbon, Palygorskite and albite. These minerals have undergone alteration and are associated with gold-carrying minerals. These minerals are much found on Andesite rocks. So it can be estimate that the type of rock in the area is Andesite. The analysis result of mineral type on rock samples 2 is Kaolinite, Organic Carbon, Palygorskite, and Quartz. These minerals are much found on limestone and quartzite rocks. So it can be estimate that the type of rock in the area is Limestone and Quartzite.
Thus the results of this study can show that in accordance with the geological structure and tectonic history, that Buru Island consisting of metamorphic rock (filit, skist and quartzite), sedimentary rocks (rocks) and volcanic rock (tufa andesite and basalt). The types of rocks found in the area of Botak Mountain, Buru Island is very influential on the process of forming gold in this area. The Andesite, quartzite and limestone that are teralterasi are members of the Alluvium Formation. The rocks that are most affected and serve as rock traps (traps) for the occurrence of mineralization are limestone and quartzite. For rocks that are interpreted as gold metal carriers are basaltic andesite veins.

CONCLUSIONS
The analysis results of mineral type on rock samples 1 and 3 have similarities that are dominated by Kaolinite, Organic Carbon, Palygorskite and albite. These minerals undergone changes and are associated with gold-carrying minerals. This mineral much found in the Andesite rocks. So it can be estimated that types of rocks in the area are Andesite. The analysis results of mineral type on rock samples 2 were Kaolinite, Organic Carbon, Palygorskite, and Quartz. This mineral much found in the Limestone and quartzite rocks.
The existence of the Andesite shows that there has been a change and hydrothermal mineralization on volcanic origin rocks. So it can be estimate that these rocks are the bearing rocks and hosted rocks of base metals and gold. Whereas the limestone and quartzite is a bond mineral from gold carrying rock.