Gold Mining Discussion

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Saya ucapkan TERIMA KASIH BANYAK untuk para pembaca setia Hydrogeology World dan para pembaca yang menjadi kontributor selama saya ada proyek dengan USGS. Saya MOHON MAAF selama hampir setahun tidak bisa update informasi dalam blog ini. Terus ikuti blog ini karena mulai sekarang saya akan update blog ini sesering mungkin dengan tambahan informasi-informasi yang berguna, semoga bermanfaat.

Hormat saya,

Alva Kurniawan

THANKS SO MUCH AND I’M SO SORRY

THANK YOU VERY MUCH for Hydrogeology World’s reader and the reader who becomes contributor when I was on project with USGS. I’M SO SORRY that in close to one year I could not update the information in this blog. Please keep reading this blog because I will update the information in this blog as often as possible with a lot of useful information.

Regards,

Alva Kurniawan

Figure 1. Spatial model of caves

The model comprises of three main things such as cavities, water, and limestone. The true resistivity value of water would be 10-100 Ohm meter, and then for limestone would be 40-500 Ohm meter (Loke, 2000). The cavities would have different true resistivity values, the cavity that is fully filled with air would have very high resistivity value (the resistivity value of air was defined in 2000 Ohm meter). The cavity that filled with little amounts of water would have smaller resistivity value then the resistivity value would be getting smaller as the increasing of water amounts on the cavity. The resistivity model that represent the spatial model of caves is shown on Figure 2.

Figure 2. Resistivity model of cave's cavities

Simulation of DC current injection was conducted on the resistivity model by using Res2DMod software. Double Dipole configuration was chosen because of its advantages, better data resolution and less noises (Bernard et al, 2004).The result of apparent resistivity calculation from resistivity model is shown on Figure 3. Noises of apparent resistivity value from the calculation is assumed as 0 %. The real condition of caves environment actualy contributes high noise on the apparent resistivity calculation so 10 % noise value was put on the data to represent the real condition.

Figure 3. Apparent resistivity calculation from resistivity model

Res2DInv software was used for calculating true resistivity value from calculated apparent resistivity value of the model. Combination of Marquardt-Smoothness Constrained Least Square Inversion was chosen to get better result of resistivity pseudosection (Figure 4). Based on resistivity pseudosection, cavity that is fully filled with air would be easier to be detected by its high resistivity value, then cavity that is fully or mostly filled with water would be easier to be detected by its low resistivity value. The cavity that is filled with little amounts of water would be harder to be detected because the resistivity pattern on the resistivity pseudosection appears in disordered shape that not represent a cavity shape.

Figure 4. Resistivity pseudosection of cave's cavity

REFERENCES:
Bernard, Jean, & Orlando Leite, Fabrice Vermeersch. 2004. Multi-Electrode Resistivity Imaging for Environmental and Mining Application. Orleans: IRIS.
Loke, M. H. 2000. Electrical Imaging Survey for Environmental and Engineering Studies. 06/03/2009. http://www.geometrics.com.
Zhou, W., & B. F. Beck, J. B. Stephenson. 2000. Reability of Double-Dipole Electrical Resistivity Tomography for Defining Depth to Bedrock in Covered Karst Terranes. Environmental Geology, 39, 7.

HW’S WAT-B is software for Water Balance calculation from rainfall and evapotranspiration data. HW’s WAT-B is easy to be used and also it could be used and compatible in all versions of Windows (including Windows Vista and Windows 7).  Unfortunately this software only has image file as an output (printscreen image) and this software couldn’t be used as database software. Overall, this software is very useful for compiling Water Balance report.

This software is free, click this link below to download it

Download HW’S WAT-B

Block modeling of rho data could be conducted to obtain the three dimension distribution of rho value. Research was conducted on Gunungsari Hill in Magelang, Central Java Indonesia. The main purpose of this research was for proving that two dimensional rho data can be modeled into block model while they were crossed.

Rho data was obtained from ten boreholes on the peak of Gunungsari Hill. Each borehole coordinate was plotted on Rockworks software. Block model was created by interpolating rho data on boreholes within Anisotropy Inverse-Distance Algorithm.

Interpolation of two dimensional rho data from crossed boreholes lines formed block model. Crossed lines acted as planes in four directions those formed blocky shaped model. Making rho block model with crossed boreholes lines is recommended for project with limited funding.

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Stratigraphical Interpretation of Gunungsari from Gunungsari ERT Survey

According to Shearer and Ashmore (1979), resistivity detector is a kind of instrument which is used on archeological site ground reconnaissance. However, Shearer and Ashmore (1979) stated that resistivity detector was not widely used in the past because it more time consuming and less successful than magnetometer. Nowadays resistivity detector method is starting to be applied commonly in archeological ground reconnaissance due to the advancing of the new technique. The technique is called ERT or electrical resistivity tomography. ERT Survey took place in the peak of Gunungsari Hill. Gunungsari Hill administratively was located in Salam District, near Muntilan City. Salam District is a part of Magelang Regency, Central Java Province. This survey’s main purpose was to discover the missing part of the temple ruin that was suspected below the temple area’s ground.

This research consists of several steps such as litterateur study and field observation, ERT survey, ERT data processing, and then ERT data interpretation and buried objects identification. ERT survey used Wenner Schlumberger array, an electrode configuration which has good vertical and horizontal coverage but it also has vertical and horizontal distortion. Processing ERT data in this research was carried out by X2IPI and Res2DInv software. Data interpretation was conducted by considering about Gunungsari Hill archeology, culture, history, geomorphology, geology, hydrogeology, geophysical characteristic, and also distortion effect of used array.

ERT survey can provide a subsurface map that contains information about both of horizontal and vertical location of buried objects. ERT survey is also easy to be conducted and also it has good precision if the interpreter knew much about the survey area characteristics. ERT survey result on Gunungsari Hill provides information that there are 11 buried andesitic materials those are strongly suspected as buried temple parts. They are located from just few centimeters to a half mater below the surface

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TOmography Result in Identifying Ammonia Waste Distribution

Electrical Resistivity Tomography or ERT can be used to analyze the distribution of chemical waste below earth surface. ERT survey was applied in Piyungan Garbage Disposal Center that produces a fair amount of ammonia in liquid form. Elcetrode configuration that was applied was Wenner-Schlumberger within 44 meters long tomography line.

Picture above shows the result of ERT in Piyungan. Based on the picture, ammonia waste can be seen infiltrated below earth surface. Ammonia waste just infiltrated in certain location where dominated with clay or sandy materials.

Result of IP Data Interpretation for Gold Prospecting

Induced polarization is the one of the geosounding method that widely used by geologist to estimate the mineral deposits. Induced polarization basic concepts is measuring the frequency effect or FE from injected electricity with different frequency. Frequency effect is the difference between first measured resistivity value and the second measured resistivity value. Electrode configuration that used in this survey was double dipole array. Processing the data from IP survey used Res2DInv software and for identifying the gold potential part of the pseudosection, flash MX software was used.

Gold mineralization in the survey area is associated with high frequency effect value zone that estimated as the zone of argilic alteration. Gold generally deposited near intrusion zone in veins form. From interpreting the fracture zone overlaid with intrusion zone and zone of high frequency effect, the area which has high potential of gold deposit can be estimated. Based on picture above, the area where gold may be present lay in the middle or upper part of diorite intrusion zone.