Int. j. econ. env. geol. Vol: (2) 12-20, 2012
ÓSEGMITE
Available online at www.econ-environ-geol.org
Introduction
Environmental pollution related to urbanization and industrialization is inevitable unless proper measures are taken. Air pollution is one of the serious problems in recent times as a result of rapid increase in number of vehicles, cement factories, steel and coal industries and petrochemical industries coupled with deforestation of natural forest. In comparison to the effect of gaseous pollutants on the air quality, little attention is given to the effect of particulate pollutants on soil and vegetation properties (Muhammad and Muhammad, 2001; Abdulrasoul et al., 2011; Princewill et al., 2011). Soil is a mixture of minerals, organic matter and water capable of supporting plant life on the earths surface. It is the final product of the weathering action by physical, chemical, and biological processes on parent rocks (Manaham, 2000). The physicochemical characteristic of a soil at a given site is highly governed by pH. When measured at the same time as pH, measurement of conductivity is also a good indicator of soil quality. Adsorption of exchangeable cations during deterioration processes represents the net accumulation of materials at the interface of the solid phase and the soil solution at a given pH (Marc and Jacques, 2006).
Air pollutants such as heavy metals (HM), generated in the process of crushing limestone, bagging, and transportation of cement are carried by wind and deposited on soil, plants and water bodies (Kabir and Madugu, 2010). Globally, the problem of environmental pollution due to heavy metals has been a concern in most cities
Assessing the Effect of Cement Dust Emission on the Physicochemical
Nature of Soil around Messebo area, Tigray, North Ethopia
SAMUEL ESTIFANOS* and AYNALEM DEGEFA**
Department of Earth Sciences, Mekelle University,
College of Natural and Computational Sciences, Mekelle, Ethiopia
E-mail: sambersih@yahoo.com*; aynalem241@gmail.com**
for it leads to geoaccumulation, bioaccumulation and biomagnifications in ecosystem (Princewill et al., 2011). Among the metals especially recognized in environmental studies on emission from cement plants to have toxic effect on soil are arsenic, cadmium, lead, mercury, thallium, aluminum, beryllium, chromium, copper, manganese, nickel and zinc (Addo and Darko, 2012). Some researchers investigated the impact of the cement dust on soil properties and plant growth (Muhammad and Muhammad, 2001; Emmanuel and Edward, 2010; Ahiamadjie and Adukpo, 2010; Princewill et al., 2011; Al-Oud et al., 2011; Addo and Darko, 2012). Determining the physicochemical properties of soil and their trace metal content is important to monitor environmental pollution related to cement industries. Arpita and Mitko (2011) reported that top soils near a cement factory are enriched in Pb, Zn, Cr, Cd, V, Pb and Hg which are released into the air from the cement kilns. Khashman and Shawabkeh (2006) revealed that the area close to cement factory in southern Jordan has highest lead, zinc and cadmium level. Zerrouqi et al., (2008) accounted that calcium oxide and sulfur oxide are the principal component of pollution on soil surrounding cement factory on Morocco. The results of elementary chemical analysis, expressed in weight percent of oxides, conducted by (Young-Chull and Jae-Min, 2004) showed that the raw material dust of the first grinding process primarily consisted of CaO (41.77), SiO2 (11.72%), Al2O3 (3.45%),
and Fe2O3 (1.47%). From Ca/Si ratios computed by
Asubiojo (1991), it was found that soil contamination due to cement drops sharply with distance from the Abstract. Twenty six soil samples were collected around the vicinity of Messebo cement factory in Mekelle, Ethiopia from 0-5 and 5-15 cm depths and determined their physicochemical properties and heavy metals contents. The results indicated that the soils are calcareous having sandy loam to loamy sand texture. The top and lower parts of the soil are found to be alkaline with mean pH 8.97 and 8.93; EC 223.06 and 88.22 µS/cm respectively. The cation exchange capacity of the top soil (0-5cm) range from 9 to 27 mmolc kg-1, while the exchangeable Ca and Mg range from 6.4 to
16 and 2.2 to 5.0 mmolc kg-1 respectively. The average Ca concentration values for the upper and lower soil depths
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factories, and with increasing depth from the surface. Messebo cement factory was established in 2000 to produce 2000ton of clinker per day for 300days a year. Its capacity was expanded since 2011with addition of new plant totaling 5000ton of clinker per day and introducing coal as energy source in addition to the heavy oil for the clinker furnace. The factory is suited on the Messebo Limestone Formation which is the major raw material for cement production. Though the new plant has latest technology for efficient use of energy and reducing emissions, the older one has visible impact on the surrounding environment through, mainly, dust from quarry mines, crusher and from the clinkers and water effluences that could possibly cause soil degradations in the nearby areas. As a result of the expansion of Mekelle City towards the factory vicinity, other impacts on the environment include gases (air pollution), heat (thermal pollution mainly through hot effluents) and noise pollution. This paper presents results of assessment of the impact of cement dust from the cement factorys old plant on
normally blows strongly with maximum speed of 160m/s from the SE to NW for nine months of the year (September up to May) and reverses its direction in the rainy season i.e. June to August (Benjamin, 2005), (Fig. 2).
Materials and Methods
Soil sampling in the vicinity of Messebo cement factory where the dust is visually evident to fall predominantly was conducted in March, 2012. Twenty six samples each weighing ½ Kg were collected from 13 spots in a random sampling pattern two samples from each spot. Six of the spots fall on farm land while seven are on fallow land (Fig. 1). The surface soil in the upper 5 cm layer and lower 5cm to 15cm were sampled in each spot to examine the effect of dust on the fallow and farm soil. Rock fragments and organic matter were removed. All the samples were subjected to geochemical laboratory at Mekelle University for physicochemical analysis. The soil samples sieved to <2mm size were digested by
Fig. 1. Location map of study area and sampling spots
Fig. 2. Predominant Wind Direction around Messebo (January to July, 2005)
the physicochemical characteristics of soil in the surrounding area. The pollution assessment would help to present the existing soil quality and to predict possible additional impact due to the emissions expected from the new factory.
aqua regia (nitric acid + hydrochloric acid, in a 1:3 volume ratio) prior to determining the major cations by atomic absorption spectrometry (AAS: varian spectrometer AA-400, flame atomic absorption spectrometer, stand alone system); trace elements by Unicam 929AA Spectrophotometer whose detection limit and Wavelength range is presented in Table 7 as well as anions by UV-Spectrophotometer (Shimadzu UV mini 1240) respectively. One gram of each sample was mixed with 20 ml aqua regia stirring at 100oC for 20 minutes heated
on a hot plate. Then 20 ml of 0.1N HCl, prepared by a mixture of 8.2 ml concentrated HCl and 1000 ml distilled water, was added drop by drop to the digested samples and shaken for 2 minutes. The resulting solution was filtered by adding distilled water till the filtrate gets 50 ml volume before cation and trace metals measurements were done by respective atomic absorption spectrometry instruments. In both cases, ICP multi-element standard solution IV UN-2031 was used. This digestion method is based on US Standard Methods for the Examination of Water and Wastewater, 3030. The pH and EC was measured by preparing a solution 10 g of original sample with 50 ml distilled water and shaken well in shaker. On
the other hand, 10 gm of each sample was treated with de-ionized water, shaken for 2 hours and filtered prior to analysis using the UV-Vis Spectrophotometer to determine the anions in water soluble phases by Spectroquant methods.
To determine the exchangeable cations, the soil samples were leached with a solution of potassium chloride where 5 g of dry soil sample was mixed with 25 ml potassium chloride (KCl) solution in a clean 50 ml beaker. Then the solution was filtered with filter paper in a funnel over a 100 ml collecting bottle. After leaching the soil with 3 further 25 ml portions of KCl, allowing each to drain before adding the next (total of 100 ml leaching solution), the leachate was retained for analysis of Ca, Mg and acidity once drainage has stopped. In the leachate, exchangeable calcium and magnesium are determined by AAS and the exchangeable acidity was determined by titration against standard sodium hydroxide solution. Ignoring the generally small contributions from exchangeable Na and K, effective cation exchange capacity (CEC) was calculated as the sum of exchangeable Ca, Mg and acidity.
Repeat analyses on three randomly selected samples were performed and reagent blanks and standards were used to assure quality control of analysis. The precision and bias were generally <10% (Table 1).
Heavy metals pollution indicator, geo-accumulation index (Igeo), was computed as applied by a number of workers such as (Krupadam et al., 2006; Emmanuel and Edward, 2010; Abdulrasoul et al., 2011).
5 . 1 log2 n n B C Igeo =
Where Cn represents the measured total concentration
of metals in the soil (mg/kg); and Bn represents the
Parameters 0- 5 cm depth 5- 15 cm depth
Max Min Mean StDv Max Min Mean StDv
EC, µS/cm 432.00 108.00 223.06 96.75 161.80 47.60 88.22 36.69
pH 9.67 8.55 8.97 0.28 9.26 8.37 8.93 0.25
Na, ppm 481.00 147.00 395.85 90.63 556.00 104.00 352.18 145.38
K, ppm 13.00 7.00 9.93 1.99 15.60 5.00 9.54 3.06
Ca, ppm 516.00 346.00 431.77 53.33 562.00 313.00 404.36 86.80
exch. Ca, mmolc kg-1 16.60 6.40 11.50 7.21 16.4 19.6 18.00 2.26
Mg, ppm 216.00 102.00 163.31 42.10 202.00 98.00 134.55 35.80
exch. Mg, mmolc kg- 1
5.00 2.20 3.60 1.98 9.20 4.60 6.90 3.25
CEC, mmolckg -1
27.00 9.00 18.00 12.73 35.00 24.98 29.99 7.09
Cl, ppm 223.00 104.00 136.31 31.22 218.00 108.00 144.18 34.38
HCO3, ppm 992.00 312.00 692.23 229.34 1011.00 206.00 561.36 298.78
SO4, ppm 542.00 218.00 409.23 96.60 516.00 318.00 444.36 74.01
Table 2. Summary for the major physicochemical parameters of the soil around the cement factory Table 1. Comparison of first and repeat analysis
Cr 0.17 0.16 5.88
Cu 2.80 2.90 3.57
Pb 0.53 0.51 3.77
As 1.62 1.60 1.23
Co 0.74 0.75 1.35
Zn 12.27 12.30 0.24
Mo 2.43 2.33 4.12
Ca 95.00 94.67 0.35
Fe 143.00 142.00 0.70
Ni 0.25 0.27 6.58
Metals
Average trace metal Concentration, ppm
First Repeat Difference
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geochemical background values of the metals (mg/kg). For the analysis of the geochemical background values of heavy metals (Bn), five uncontaminated surface soils
were collected from undisturbed area at about 5km distance form the study area (Fig.1), where both anthropogenic and industrial activities are minimal and can represent geological background with reference to heavy metals. The constant 1.5 is introduced to minimize the effect of possible variations in the background values which may be attributed to lithologic variations in the soils (Emmanuel and Edward, 2010; Sampson and Francis, 2011).
Seven ranges of contamination values have been determined to assess the degree of trace metals pollution (Al-Khashman and Shawabkeh, 2006):
Igeo = 0 refers to unpolluted
0 < Igeo < 1 refers to unpolluted to moderately polluted 1 = Igeo< 2 refers to moderately polluted
2 = Igeo< 3 refers to moderately to strongly polluted 3 = Igeo< 4 refers to strongly polluted
4 = Igeo< 5 refers to strongly to very strongly polluted Igeo = 5 refers to very strongly polluted
Moreover, the Enrichment Factor (EF) was calculated as described by (Akoto et al., 2008; Emmanuel and Edward, 2010; Karbassi et al., 2011).
reference C C soil C C EF Fe x Fe x ) ( ) ( =
Where (Cx / CFe)soil = (the concentration of a metal
divided by the concentration of Fe in the soil from the study area) and (Cx / CFe)reference = (the concentration
of a metal divided by the concentration of Fe in an unpolluted soil).
The pollution magnitude of the trace metals in the soil is to be evaluated by the following classification for EF (Al-Khashman and Shawabkeh, 2006):
EF < 2 is for deficiency to minimal enrichment EF 2-5 is for moderate enrichment
EF 5-20 is for significant enrichment EF 20-40 is for very high enrichment EF > 40 is for extremely high enrichment Larger EF values show more contribution of the anthropogenic origins (Al-Khashman and Shawabkeh, 2006).
Results and Discussion
The basic physiochemical properties of the soil samples are summarized in Table (2). The texture of the soil ranges from sandy loam, to loamy sand in most cases. The soil is calcareous in nature with average Ca content of 418ppm. Moreover, the pH values range from 8.37 to 9.67 while the EC values range from 47.6 to 432 µS/cm with an average value of 155.64 µS/cm. This shows that the soil
is saline to alkaline compared to reference soil with mean pH value of 7.48. On the other hand, Ca, Mg and Na are the most dominant cations whereas Cl, HCO3 and SO4
are the most dominant anions. The cation exchange capacity of the top soil (0-5cm) range from 9 to 27 mmolc
kg-1, while the exchangeable Ca and Mg range from 6.4
to 16 and 2.2 to 5.0 mmolc kg-1, respectively. The mean
CEC of the lower soil depth, which is 18 mmolc kg-1 is
much higher than that of the upper soil depth (5-15cm), 29.9 mmolc kg-1 implying that the lower part is more
organic rich loam soil (Seybold et al., 2005).
The upper soil portion (0-5cm) generally showed similar mean values with lower soil portion (5-15cm) for pH and K, Mn, Cr, Si, Pb and Ni concentration. The upper part have significantly higher mean concentration of EC, Na, Ca, Mg, Fe, Cu, As and Zn than the lower part which in turn has higher mean values of exchangeable Ca and Mg, Cl, SO4, Mo and Co (Table 2 and 3). Average cation
exchange capacity of the soil was found to be higher in the lower depth than in the upper layer. Conversely, the mean electrical conductivity (EC) of the top most part of the soil is much higher than the lower layer. The higher EC values of the upper soil layer can be attributed to higher mean concentration of the major cations (Ca, K, Mg and Na) and anion (HCO3) in the soil. Mean EC
values 223.06 µS/cm for upper part is much higher than the mean EC value of the reference soil, 88.63 µS/cm, which is similar with the lower part having mean EC of 88.2 µS/cm. High EC value in soils is due to the concentration of salt in the soil. Industrial saline wastes and irrigation are the main human activities that add salts to the soil (Hinrich, 2001). There is no irrigation activities in the study area and thus the higher values of EC have to be related to the dust emission from the cement factory. The north western part of the study area towards which the wind predominantly blows is characterized by comparable values of pH and Cr in both soil depths (Fig. 3A-H). It was noted that higher values of such parameters as pH, Cu, Zn and Ni were detected in the top soil than in the lower soil layer very close to the factory. However, EC, Cu, Pb and As are higher in the top soil than lower soil samples collected from the central part of the area. Zn has higher values in the lower as well as comparable values in both depths on samples far away from the plant (Fig. 3F). At close distance from the factory, the upper soil layer exhibits higher Zn values than the lower part of the soil that can be due to recent deposition of the polluting dust. This is explained by the fact that Zn is known to have higher mobility in soil profile as shown by Luke et al., (2010) and Rosazlin et al., (2010). Likewise, Ni shows similar spatial trend and is known to have higher mobility in carbonate soils as reported by Lafuente et al., (2008).
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concentration in the upper layer than in the lower on the northern side of the facory; while the reverse is true on samples close to the factory. The study on heavy metals mobility conducted by Lafuente et al., (2008) showed that Cr and Pb are the least mobile metals in carbonate soils. Chromium in the study area shows no preferential enrichment in either of the depths implying even distribution of the metal in the soil (Fig. 3H). The major source and possible reason for the elevated As concentration is coal dust and coal combustion of the cement factory. Upon coal combustion, Arsenic is released from the coal matrix and is distributed between the vapor and particulate. Arsenic is concentrated in particles as well as also in volatile form that eventually falls down (Vimal et al., 2011). Relatively higher As2O3 content was
reported in lignite (low grade coal) by Ersan et al., (2001). Samples from the western side of the study area are under relatively higher influence of the road dust. The discussion of lead, zinc, copper, chromium and nickel values due to the dust from the factory is complicated on these samples since the metals are also associated with automobile-related pollution in roadside dusts (Duzgoren-Aydin et al., 2006; Babatunde and Oladewa, 2012). The mean values of the metals concentration in both soil depths are found to be higher than their corresponding mean values in the reference area. In the upper soil layer, the metals have values in decreasing order as: Zn>Cu>As>Ni>Mo>Co>Cr>Pb while the decreasing order in the lower soil layer is Zn>Cu>Mo>As>Ni >Co>Cr>Pb (Fig. 4). The concentration values of Zn and Cu are found to be higher whereas that of Pb values are the lowest. Such result was also reported by (Al-Khashman and Shawabkeh, 2006; Abdulrasoul et al., 2011; Princewill et al., 2011) reported Pb to be the highest.
All the metals except Mo, Pb and Co have higher mean values in the upper depth with Pb having the same value in both depths. The possible reasons for this and even for Mo and Co to have higher mean values in the lower part can be the mixing up of the top soil by farming and downward leaching of the metals. Though samples collected from farm soil experiences mixing up of the top soil by ploughing, it is not possible to believe that such mixing has resulted in the generally erratic distribution of the elevated values of the metals in both depths. This is because preferential distribution of the trace metals is not evident even in the samples of both depths collected from fallow soil (Fig. 4A&B). It is also possible to note that the mean values of the water extractable portion of all the metals in the lower part is higher than that in the upper part of the soil (Table 4). The water soluble portion of the metals refers to the detached cations from their crytalline mineral structure or to anthropogenic loadings of the metals (Joan et al., 1992). Detaching the metals from their minerals needs vigorous acid attack which is not possible to happen in nature. Water extractable phase contains most mobile and bio-available metals and are useful in the study of metal uptake by plants and soil invertebrates, where transfer takes place predominantly from a water solution phase (Bhupander et al., 2011). Based on the water extraction result, Cu has the highest whereas Pb has the least water soluble proportions in both soil depths. Mo has significantly higher water soluble proportions in the lower depth compared to the upper soil depth. Higher total concentration of Mo and Co in lower soil depth as shown in Figure 4 is good indication of the probable downward leaching of the metals.
The Geo-Accumulation Index (Igeo) and Enrichment Factor (EF) of the trace metals in both depths of soil near Parameters 0- 5 cm depth 5- 15 cm depth Heavy metals concentration(ppm) in soils of reference
area*
Max Min Mean StDv Max Min Mean StDv Max Min Mean
Fe 1016.0 702.0 897.1 85.1 983.0 524.0 810.8 163.6 202.00 101.00 143.00
Mn 78.0 2.5 46.4 17.4 58.0 9.8 45.5 17.6 0.26 0.01 0.14
Cr 68.0 4.1 40.4 20.6 58.0 3.1 39.5 18.3 0.23 0.13 0.17
Cu 131.0 18.0 102.5 27.7 115.0 54.0 92.4 23.8 3.10 2.50 2.80
Mo 102.0 32.0 63.3 35.6 113.0 52.0 91.7 34.4 3.20 1.80 2.43
Pb 12.0 2.0 7.0 3.0 11.0 4.0 7.0 1.9 0.63 0.42 0.53
As 126.0 46.0 98.5 24.3 116.0 46.0 90.7 26.4 2.31 0.98 1.62
Co 112.0 18.0 55.6 25.1 113.0 28.0 78.2 32.0 0.93 0.56 0.74
Zn 253.0 108.0 155.2 53.4 164.0 108.0 126.5 20.8 98.00 11.50 43.49
Ni 113.0 50.0 87.7 25.2 117.0 39.0 87.4 29.5 0.41 0.12 0.25
*Reference samples were collected as composite of the top 15cm soil from unpolluted area 6km away from the factory against the wind direction
Fig. 4. Mean concentration of the total analysis of the heavy metals in both depths (A) and comparison of farm and fallow soil in both depths (B).
Table 4. Heavy metals water extractable values (ppm) and their proportion with the total analysis result (%) in both depths
Sample depth Cr, ppm Cr, % Cu, ppm Cu, % Mo, ppm Mo, % Pb, ppm Pb, %
Upper part 0.67 16.50 38.00 36.10 35.67 17.65 0.30 4.22
Lower part 1.95 24.69 51.40 49.77 40.00 46.01 0.77 6.52
Sample depth As, ppm As, % Co, ppm Co, % Zn, ppm Zn, % Ni, ppm Ni, %
Upper part 22.00 19.74 12.67 23.37 26.67 18.84 25.00 24.60
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the cement factory were computed. The (Igeo) and (EF) results are presented in Table (5) and Table (6) with the pollution classification of the trace elements. Accordingly, the soil of the study area under consideration can be categorized as moderately to heavily contaminated with Zn in the lower part and heavily contaminated with Zn in the upper part and Pb in both depthes. Cr, As, Co and Ni have the highest pollution indexes in both soil depths with Igeo > 4. Alternatively, Ni (EF>40) has the highest enrichment in both soil layers while Zn (EF<2) has the lowest enrichment in lower part of the soil respectively.
Conclusion
Based on the results of this research, it can be concluded that the two soil depths investigated are similarly categorized as very heavily contaminated with (As, Cr, Co and Ni) and moderately to strongly polluted with (Cu, Pb, Zn and Mo) while the top part is moderately polluted with Zn. On the other hand, according to the EF results, the both soil depths have moderate enrichment with Pb (2 < EF < 5), significant enrichment with As and Cu (5 > EF >20), very high enrichment with Cr (20 < EF < 40) and extremely high enrichment with Ni (EF > 40). The sever contamination is evident to the western and northern direction towards which the wind blow predominantly. The research has clearly determined that the soil
physicochemical property is affected by the dust emission from the factory.
Acknowledgement
The authors wish to express their deep gratitude to the geochemical laboratory staff of Earth Sciences Department in Mekelle University for diligently and carefully analyzing the soil samples.
References
Abdulrasoul, M; Al-Omran; Salem, E; El-Maghraby; Mahmoud, E.A; Nadeem, A; El-Eter, M; Salem M.I; Al-Qahtani. (2011) Impact of cement dust on some soil properties around the cement factory in Al-Hasa Oasis, Saudi arabia. American-Eurasian, J. Agric. & Environ. Sci, 11(6), 840-846.
Addo, M.A; Darko, E.O. (2012) Evaluation of heavy metals contamination of soil and vegetation in the vicinity of a cement factory in the Volta region, Ghana. Int. J. Science and Technology, 2, 1. Ahiamadjie, H; Adukpo, O.K. (2010) Determination of
the elemental contents in soils around diamond cement factory, Aflao. Research Journal of Environmental and Earth Sciences, 3(1), 46-50. Akoto, O; Ephraim, J.H; Darko, G. (2008) Heavy metals
Cr 8.1 4 7 73.1 3.7 38.9 7.8 3.6 6.9 59.8 4.9 39
Cu 5 2.1 4.5 8.9 1.1 5.9 4.8 3.7 4.4 10.9 3 6
Mo 4.8 3.1 4 6.5 2.1 4.2 5 3.8 4.6 12.7 3.2 9.4
Pb 3.9 1.3 3 3.5 0.6 2.1 3.8 2.3 3.1 5.6 1.3 2.5
As 5.7 4.2 5.3 12.8 4.2 9.8 5.6 4.2 5.2 19.5 4.4 10.6
Co 6.7 4 5.5 21.3 4.3 11.9 6.7 4.7 6 41.7 7.7 20.1
Zn 3.8 2.6 3 8.9 1.3 2.6 3.2 2.6 2.8 2.6 1.3 1.9
Ni 8.2 7.1 7.8 77.3 31.8 55.6 8.3 6.7 7.7 73.3 29.7 57.5
Metals
0- 5 cm depth 5 15 cm depth
Igeo EF Igeo EF
Max Min Mean Max Min Mean Max Min Mean Max Min Mean
-Table 5. Heavy metals geo-accumulation index and enrichment factor of soil around the cement factory
Moderately to strongly polluted - Zn
Strongly polluted Pb, Zn Pb
Strongly to very strongly polluted Cu, Mo Cu, Mo
Very strongly polluted Cr, As, Co, Ni Cr, As, Co, Ni
Deficiency to minimal enrichment - Zn
Moderate enrichment Mo, Pb, Zn Pb
Significant enrichment Cu, As, Co Cu, Mo, As
Very high enrichment Cr Cr, Co
Extremely high enrichment Ni Ni
Pollution index classifications Upper part Lower part
Igeo
EF
pollution in surface soils in the vicinity of abundant railway servicing workshop in Kumasi, Ghana. Int. J. Environ. Res, $(4), 359-36.
Al-Khashman, O.A; Shawabkeh, R.A. (2006) Metals distribution in soils around the cement factory in southern Jordan. Environ. Poll, 140, 387-394. Al-Oud, S.S; Nadeem, M.E.A; Al-Shbel, B.H. (2011) Distribution of heavy metals in soils and plants around a cement factory in Riyadh city, central of Saudi arabia. American-Eurasian J. Agric. & Environ. Sci, 11(2), 183-191.
Arpita, M; Mitko, V. (2011) Heavy metals in soils around the cement factory in Rockfort, Kingston, Jamaica. Int. J. Geosciences, 2, 48-54.
Asubiojo, O.I; Aina, P.O; Oluwole, A.F; Arshed, W; Akanle, O.A; Spyrou, N.M. (1991) Effects of cement production on the elemental composition of soils in the neighborhood of two cement factories, water, air, and soil pollution. Kluwer Academic Publishers, 57-58, 819-828.
Babatunde Saheed Bada and Oladewa Titilope Oyegbami. (2012) Heavy metals concentrations in roadside dust of different traffic density. J. Environment and Earth Science, 2, 8.
Benjamin, J. (2005) Wind data evaluation after 6 months. Wind energy programme TERNA Ethiopia deutsche gesellschaft für technische zusammenarbeit (GTZ) gmbH Dag-Hammarskjöld-Weg 1-5.
Bhupander, K; Sanjay, K; Meenu, M; Singh, S.K; Dev Prakash; Sharma1, C.S; Mukherjee, D.P. (2011) Geochemical fractionation of some heavy metals in soils in the vicinity of sukinda mining area, Orissa. Advances in Applied Science Research, 2(5), 263-272.
Duzgoren-Aydin, N.S; Wong, C.S.C; Song, Z.G; Aydin, A; Li, X.D; You, M. (2006) Fate of heavy metal contaminants in road dusts and gully sediments in Guangzhou, SE China: A chemical and mineralogical assessment. Human and Ecological Risk Assessment, 12, 374-389.
Emmanuel Olubunmi Fagbote and Edward Olorunsola Olanipekun. (2010) Evaluation of the status of heavy metal pollution of soil and plant (Chromolaena odorata) of Agbabu Bitumen deposit area, Nigeria. American-Eurasian Journal of Scientific Research, 5(4), 241-248.
Ersan Kalafatog Lu; Nuran Örs; Sibel Sain Özdemir; Ismet Munlafaliog Lu. (2001) Trace element emissions from some cement plants in Turkey. Water, Air, and Soil Pollution, 129, 91-100.
Hinrich, L.B; Brian, L.M; George, A. OConnor. (2001) Soil Chemistry. Third edition, John Wiley & Sons, Inc. USA.
Joan, E; McLean; Bert, E.B. (1992) Behavior of metals in soils. United States Environmental Protection Agency. EPA/540/S-92/018.
Kabir, G; Madugu; A.I. (2010) Assessment of environmental impact on air quality by cement
industry and mitigating measures: A case study. Environ Monit Assess, 160, 91-99.
Karbassi, A.R; Torabi, F; Ghazban, F; Ardestani, M. (2011) Association of trace metals with various sedimentary phases in dam reservoirs. Int. J. Environ. Sci. Tech, 8(4), 841-852.
Krupadam, R.J; Smita, P; Wate; S.R. (2006) Geochemical fractionation of heavy metals in sediments of the tapi estuary. Geochemical Journal, 40, 513-522. Lafuente, A.L; González, C; Quintana, J.R; Vázquez, A; Romero, A. (2008) Mobility of heavy metals in poorly developed carbonate soils in the mediterranean region. Geoderma, 145, 238244.
Luke, B; Eduardo, Moreno-Jime´nez; Rafael, C; Nicholas, L; Nicholas, D. (2010) Mobility of arsenic, cadmium and zinc in a multi-element contaminated soil profile assessed by in-situ soil pore water sampling, column leaching and sequential extraction. Environmental Pollution, 158, 155-160.
Manahan, S.E. (2000) Soil Environmental Chemistry. Environmental Chemistry, Press LLC. Florida. Marc, P; Jacques, G. (2006) Handbook of soil analysis, mineralogical, organic and inorganic methods. Springer, 995p, Berlin, Germany.
Muhammad, Z.I; Muhammad, S. (2001) Periodical effect of cement dust pollution on the growth of some plant species. Turk J. Bot, 25, 19-24.
Princewill, C. Ogbonna; Adanma, N.N. (2011) Metal concentration in soil and plants in abandoned cement factory. Int Conference on Biotechnology and Environment Management IPCBEE, 18, Singapore. Rosazlin, A; Fauziah, C.I; Wan Rasidah, W; Rosenani, A.B. (2010) Leaching of heavy metals (Cu, Mn, Zn, Ni, Pb and As) after six months application of raw and composted recycled paper mill sludge. 19th World
Congress of Soil Science, Soil Solutions for a Changing World, 1-6.
Sampson, A.M; Francis, O.G. (2011) Contamination assessment of heavy metals in road dust from selected roads in Accra, Ghana. Research Journal of Environmental and Earth Sciences, 3(5), 473-480. Seybold, C.A; Grossman, R.B; Reinsch, T.G. (2005) Predicting cation exchange capacity for soil survey using linear models. Soil Sci. Soc. Am. J., 69, 856-863.
Vimal, C.P; Jay Shankar, S; Rana, P.S; Nandita, S; Yunus, M. (2011) Arsenic hazards in coal fly ash and its fate in Indian scenario. Resources, Conservation and Recycling, 55, 819835.
21 Int. j. econ. env. geol. Vol:3(2) 21-32, 2012
ÓSEGMITE Available online at www.econ-environ-geol.org
Introduction
Kamojang geothermal field is located in the West java province, which is approximately 60 miles southeast of Bandung. Kamojang geothermal field is bordered by several volcanoes such as Mount gandapura in the east, Mount cakra in north, Mount sanggar, Mount pasir jawa and Ciharus lake in the west and Mount jawa in the south. Geographically, this area is located at 107°47'53"-107°48'8" East Longitude and 7°00'-7°02'10" South latitude. The Kamojang field can be reached through Garut, and from here continue to the north about 21 km. The road condition is quite good until reaching the Kamojang crater where it is also a tourism area (Fig. 1.); Kamojang geothermal field was discovered by the Dutch in 1920 and exploration began in 1973 with cooperation of the Indonesia government and Newzealand. After 10 years exploration, in 1983 field production was 140 MWe, and in 1997 expanded to 220 MWe (Sudarman et al., 1995).
The purpose of this research is to conduct chemical analysis of the alteration rocks and understanding relationship of the alteration minerals. The basic principle of this method is to make a simple chart of the data of lithogeochemistry of alteration rocks. To better understand the relationship between alteration minerals and lithogeochemistry, it can be interpreted in the type of
volcanic rock prior to alteration. This method was originally used in the exploration of volcanic-hosted massive sulfide (VHMS) deposits in characterizing the intensity of alteration of volcanic rocks. This method
Alteration and Lithogeochemistry of Altered Rocks at Well KMJ-49
Kamojang Geothermal Field, West Java, Indonesia
D.F.YUDIANTORO
1, EMMY SUPARKA
2, ISAO TAKASHIMA, DAIZO ISHIYAMA
3AND
YUSTIN KAMAH
41
Geological Engineering UPN Veteran Yogyakarta, Indonesia
(Student PhD at Geological Engineering Institute of Technology Bandung, Indonesia)
2Geological Engineering Institute of Technology Bandung, Indonesia
3Centre for Geo-Environmental Science, Akita University, Japan
4Pertamina Geothermal Energy, Indonesia
email:
d_fitri4012@yahoo.com
Abstract. Kamojang geothermal field is located in a 1.2 to 0.452 Ma. Quarternary volcanic caldera system. Around the geothermal field, there are several volcanoes (cinder cones) which include: Gunung sanggar, Gunung ciharus, Gunung jawa, Gunung pasir jawa and Gunung cakra (here gunung means mount). The activity of this volcanic complex contributes greatly to the presence of Kamojang geothermal field, which forming steam dominated system
with high temperature around 250oC. The system has capacities of 260 MWe and 140 MWe. Volcanic rocks found
around the geothermal field have been altered in general and some of them are difficult to be identified their initial character. Thus, it is necessary to study alteration rocks and lithogeochemistry of a geothermal field. Based on this idea, this study uses some methods consisting of: petrographic, geochemical and alteration box plot analysis. The analyses have been conducted for the surface samples and alteration rocks of cutting from Well KMJ-49. This study is expected to improve the understanding on the characteristics of Kamojang geothermal field.
AI and CCPI calculation results indicate that the surface samples have a value ranging from 20 to 34 AI and CCPI ranges from 63 to73. While subsurface samples have AI values around 15-46 and CCPI ranges from 68 to 86. The relations of CPPI and AI will be reflected in the texture and mineralogy of the type and condition of the rock.
was previously proposed by Large et al. (2001), Paulick et al. (2001) and Herrmann and Hill (2001). In this study, the method was applied to the alteration rock due to hydrothermal processes in the Kamojang geothermal field. The lithogeochemistry analysis was conducted for the surface sample (outcrop) and cutting of alteration rocks of well KMJ-49. Petrographic and X-ray defraction (XRD) analysis was performed to observe the texture and mineralogy composition of the alteration rocks. The rock chemical data was obtained from analysis of X-ray fluorences (XRF), and then analyzed using a method of alteration box plot (Ishikawa et al., 1976) to determine the Ishikawa alteration index (AI) and the chlorite-carbonate-pyrite index (CCPI ).
According to Ishikawa et al. (1976), the alteration box plot is a graphical representation that uses two alteration indices: the Ishikawa alteration index (AI) and the chlorite-carbonate-pyrite index (CCPI).
Ishikawa AI
100(K2O+MgO)
AI= ... ...(1) (K2O+MgO+Na2O+CaO)
This index was defined by Ishikawa et al. (1976) to quantify the intensity of sericite and chlorite alteration that occurs in the footwall volcanics proximal to Kuroko deposits. The key reactions measured by the index involve the breakdown of sodic plagioclase and volcanic glass and their replacement by sericite and chlorite. Reactions that describe these alteration processes include:
3NaAlSi3O8 + K+
+ 2H+
= KAl3Si3O1 0(OH)2 +
albite sericite
6HSiO2 + 3 Na+
... .. (2) quartz
and
2KAl3Si3O1 0(OH)2 + 3H4SiO4 +9Fe2 +
+ 6Mg2 +
sericite
+18H2O = 3Mg2Fe3Al2Si3O10(OH)8 + chlorite
2K+
+ 28H+
. (3)
The first reaction is typical of sericite replacement of albite in volcanic rocks in the outer of alteration system (e.g., Date et al., 1983; Eastoe et al., 1987). The second reaction is important close to massive sulfide mineralization in footwall pipe zones where chlorite-rich assemblage become dominant over sericite-rich assemblage (e.g., Sangster, 1972; Lydon, 1988; Large, 1992; Lentz, 1996; Schardt et al., 2001). Reaction (2) involves a loss of Na2O (and CaO) and a gain of K2O, whereas reaction (3) involves a loss of K2O and gains in FeO and MgO, on the basis of constant Al2O3. Another
equation to complete the above formula is using chlorite-carbonate-pyrite index (CCPI).
100 (MgO + FeO)
CCPI= ... (4) (MgO + FeO + Na2O + K2O)
where FeO is total (FeO + Fe2O3) content of the rock.
Lentz (1996) developed a similar index to study alteration associated with the Brunswick 6 and 12 massive sulfide deposits in the Bathurst mining camp, Canada. The composite ratio used by Lentz (Fe2O3(total) + Mg)/(K2O + Na2O) has been modified in this study (eq 4) to make it comparable to the Ishikawa AI and vary between 0 and 100. One important limitation of this chlorite-carbonate-pyrite index is that it is strongly affected by magmatic fractionation and primary compositional variations in volcanic rocks.
Geology of Kamojang geothermal field. According to Robert (1988), Kamojang geothermal field is located in a large series of volcanoes which lined from the west towards the east including Mount rakutak, Ciharus lake, Pangkalan lake, Mount gandapura, Mount guntur and Mount masigit. Mount rakutak is older than Mount guntur, and both are still active. The development of these volcanoes can be observed through the alignment of magmatic center, and the development of volcanic originated from west to east. Robert, et al. (1983) and Robert (1987) indicated that Kamojang field compiled by volcanic deposits which are divided into the Pangkalan and Gandapura units in ascending order. The Pangkalan unit, age 1.20 ± 0.02 Ma, occupies the western part, while the Gandapura unit, age 0.452 ± 0.015 Ma (based on K-Ar method) occupies the eastern Kamojang. According to Kamah et al. (2003 and 2005), generally geology of Kamojang geothermal area and surroundings are composed of volcanic deposits of pre and post caldera. The sequence of pre caldera formations are basalt (Mt. Rakutak), basalt (Dog-dog), pyroxene andesite (Mt. Cibereum), pyroclastic (Mt.Sanggar), pyroxene andesite (Mt.Cibatuipis), porphyrytic andesite (Mt.Katomas), basaltic andesite (Legokpulus and Mt.Putri), andesite lava (Mt.Pasir Jawa) and pyroxene andesite (Mt.Kancing) in ascending order. The post caldera formation sequence from old to young are basaltic andesite (Mt.Batususun and Mt.Gandapura), andesite lava (Mt.Gajah), basaltic andesite (Mt.Cakra-Masigit-Guntur). The group of post-caldera formations are unconformity overlying the pre-caldera formations.
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D. F. Yudiantoro/Int. j. econ. env. geol. Vol:3(2) 21-32, 2012
Fig. 2. Geological map of research area (modified from Kamah et al., 2003)
Fig. 3. Cross section A-A showing the subsurface geology in Kamojang
Utami et al., and Browne (1999), Utami (2000) suggests that there are two hydrothermal mineral assemblages present, namely those produced by "acid" and "neutral" pH fluids. The "acid" mineral assemblage which occupies shallow levels (down to 100-300 m) consists of kaoline, smectite, alunite, quartz, cristobalite, and pyrite. The altering fluid was of acid sulphate type formed due to the oxidation of H2S. The "neutral pH" mineral assemblage occupies deeper levels and comprises varying proportion of quartz, adularia, albite, epidote, titanite, wairakite, laumontite, calcite, siderite, hematite, pyrite, anhydrite, smectite, chlorite, illite, and interlayered clays. The altering fluid was liquid of near neutral pH, and chloride-sulphate type. According to Kamah et al. (2003) alteration zone in Kamojang geothermal field can be divided into argillic and propylitic zones. Argillic zone is dominated
by clay minerals consisting of kaoline (<120o
C), smectite
(<150o
C) and smectite-illite (>200o
C) formed in acidic conditions near neutral (steam zone). The propylitic zone is assemblage of minerals that are in deeper level, has a
temperature above 200o
C in the reservoir zone. Minerals are present in this zone are epidote, adularia, wairakite, non-swelling chlorite and calcite. Purba (1994) conducted study in well KMJ-48 and KMJ-53 and found the alteration minerals.
Results and Discussion
Texture and mineralogy. The research area is a geothermal field area consists of Quaternary volcanic rocks that altered due to hydrothermal alteration. The alteration rocks were exposed on the surface around the crater with some geothermal manifestations such as: mud pool, steaming ground, fumarola and hot spring. Lava can be found on the walls of the crater and in some places exposed by erosional river water. In this study the samples obtained from surface samples and cutting samples of well KMJ-49 from shallow to the depths. The rock samples were done petrographic and geochemical analysis, whereas XRD analysis conducted on the sample subsurface only. The samples were observed on texture and mineralogical composition. The results of this analysis can be followed as follows:
Surface samples. Petrographic analysis done on 5 samples of volcanic rocks that represent some volcanoes at the research area, which: Mount Sanggar (K-9), Mount Jawa (K-23 and Mount Cakra (K-19, 27 and 35). The petrographic analysis results indicate that there are two types of rocks are: basaltic andesite and andesite pyroxene. Basaltic andesite samples owned by K-9 and the pyroxene andesite samples are K-19, 23, 27 and 35.
Basaltic andesite. Basaltic andesite volcanic rocks exposed at Mount Sanggar (K-9) is lava, gray, fine to medium grained (0.1 to 0.2 cm) with porphyritic texture. The phenocryst composed of plagioclase, pyroxene and opaque minerals are embedded in groundmass volcanic glass. These rocks have experienced partial alterated approximately 8% and alteration minerals are chlorite, clays and iron oxides. Microscopically the basaltic
andesite characterized by hypocrystaline, porphyritic, intergranular and intersertal texture. Phenocryst approximately 82-88% sized 0.2 to 1.2 mm and composed by plagioclase, pyroxene and opaque minerals. Groundmass (10-12%) generally composed of fine crystals consisting microlite plagioclase, pyroxene and opaque minerals. Some alteration minerals such as chlorite, clay and iron oxide seems to replace phenocryst on and the edge of the crystal, as well as replace some groundmass. Plagioclase looks colorless, generally present as phenocryst and groundmass approximately 72-75%. The groundmass is fine crystals consisting of Labradorite (An53-An58). Phenocryst sized 0.2 to 0.7 mm with lameral shaped prismatic subhedral-anhedral. Twinning is of Albit and combination Carlsbad-Albit. Some plagioclase shows zoning composition and some individuals of plagioclase phenocryst have been altered and show patches of secondary minerals such as chlorite and clay minerals. Pyroxene (clinopyroxene) is present approximately 5-8% as phenocryst and groundmass, prismatic shape (subhedral-anhderal) with size 0.2 to 0.4 mm. Some pyroxene have been altered, especially on their edge becoming opaque minerals and chlorite and some individual phenocrysts show corrosion by groundmass and inclusions by opaque mineral.
Opaque minerals are present around 5%, as an individual mineral, sometimes in groups and some inclusion pyroxene. In general, opaque minerals present with groundmass. Volcanic glass 10-12% occurs as finely groundmass along with microlite plagioclase and opaque minerals showing intergranular and intersertal texture.
Pyroxene andesite. Pyroxene andesitic lava is found in Mount Jawa (K-23) and Mount Cakra (samples: K-19, 27 and 35). The lava is generally slightly altered approximately 8-12%. In megascopic feature the lava is grey in colour, fine to medium grain size (0.1 to 0.2 cm) with porphyritic texture. Phenocrysts are composed of plagioclase, pyroxene and opaque minerals, embedded in the groundmass of volcanic glass. Chlorite, clay, quartz and iron oxides minerals are present as alteration minerals that alter some plagioclase, pyroxene and groundmass.
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D. F. Yudiantoro/Int. j. econ. env. geol. Vol:3(2) 21-32, 2012
replace some of the edges of plagioclase and crystal fragments. Pyroxene (clinopiroxene) is present about 12-14%, as phenocryst and groundmass, subhedral-anhderal prismatic with size 0.2-0.4 mm. Some pyroxene had been alterated, especially on the edge of crystal becoming opaque minerals and chlorite. Some individual phenocrysts show corrosion by groundmass and opaque mineral inclusion. Opaque minerals present around 3-5%, sometimes grouped in groundmass and partly as pyroxene inclusion. Volcanic glass 8-15% present as finely groundmass with microlite plagioclase and opaque minerals showing intergranular texture.
Subsurface samples. The petrographic and XRD analysis conducted for 17 samples at well KMJ-49 recognizing the presence of some secondary minerals, include:
Crystobalite.Crystobalite is generally present at shallow depths, ie <500 m depth. The presence of crystobalite ranges from 3-25% and the minerals is alteration from some of plagioclase and groundmass.
Quartz. These minerals are present in almost every depth, ranging between 5-55%. This secondary quartz may be present as the result of alteration of plagioclase, pyroxene and groundmass, as well as mineral filler in veins and cavities. As the vein filler, the quartz may be present along with calcite, anhydrite, pyrite and hematite.
Calcite. Calcite is present altering plagioclase, pyroxene and groundmass, and can be present as mineral filler of veins and cavities. Calcite can be occurred with some minerals (Fig. 4a.) such as quartz, epidote, anhydrite and pyrite. The presence of calcite ranging from 5 to 30%.
Anhydrite. Anhydrite is present as the alteration mineral resulted from replacement of plagioclase, pyroxene and groundmass. Besides as alteration mineral, anhydrite fills crystal fracture, cavities or veins along with calcite, gypsum and quartz. Presence less than 12% in the rock and occurring >300 m depth.
Chlorite. Chlorites replace plagioclase, pyroxene and groundmass (Fig. 4b). In plagioclase and pyroxene, chlorite altered the edge or the cleavage crystal. Besides as the mineral alteration, chlorite along with calcite and quartz were present as veins. The presence of chlorite ranges from 5 to 35% in the altered rocks. Chlorite swelling is present at depth less than 900 m, while unswelling chlorite were in >900 m depth.
Epidote. This mineral is present at the depth up to 950 m (Fig. 4b). This mineral is present as replacement of plagioclase and pyroxene. Some of epidote filled veins along with quartz and anhydrite. Epidote is present as alteration mineral around 8%.
Hematite. Hematite occurs as replacement of some of plagioclase, pyroxene and groundmass, and can be present to fill veins and cavities. As vein hematite comes with quartz, pyrite, clays, crystobalite and calcite. Hematite is common in shallow depths and its presence ranges between 3-12%.
Pyrite. This mineral is present in almost any depth. Pyrite occurs replacing mostly pyroxene and groundmass, and can be present as veins mineral along with hematite, quartz and calcite. The content of pyrite ranges between 2-12%.
Clay minerals. These minerals were identified using X-ray diffraction method. In general, these clay minerals are present in the altered rocks and are resulted from alteration of plagioclase, pyroxene and groundmass. Some clay minerals that are present in well KMJ-49 are: montmorillonite, illite-montmorillonite and illite. Montmorillonite is present at shallow depths, i.e <500 m. Some of montmorillonite fills fracture of plagioclase, pyroxene and some veins. Illite-montmorillonite can be found at depths between 500-900 m, along with anhydrite, calcite, quartz, pyrite and hematite. Illite, present at >900 m depths, occurs along with chlorite, epidote, quartz, calcite, hematite and iron oxide.
Alteration zone.Based on identification of mineral alteration at well KMJ-49, the hydrothermal alteration zones are crystobalite-montmorillonite, illite-montmorillonite and chlorite-epidote zones (Fig. 4-5.). Interpretation of temperature mineral alteration of each zone is shown in Table 2.
Crystobalit-montmorillonite zone.This zone is charac-terized by the presence of minerals such as crystobalite, montmorillonite, quartz, calcite, anhydrite, gypsum, hematite and pyrite. Minerals are present at <500 m depth
formed at temperatures below 100o
C (see Table 2).
Fig. 5. Composite log of hydrothermal alteration of well KMJ-49
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D. F. Yudiantoro/Int. j. econ. env. geol. Vol:3(2) 21-32, 2012
Illite-montmorillonit zone. This zone is characterized by the presence of illite-montmorillonite, calcite, anhydrite, gypsum, hematite and pyrite. Minerals are present at depth ranging from 500-900 m. Temperature interpretation of this zone is based on the formation of crystobalite and
montmorillonite minerals ranging between 100-200o
C (see Table 2.).
Chlorite-epidote. This zone is characterized by the appearance of chlorite, epidote, zoisit, illite, wairakit, hematite and pyrite. Minerals are present at > 900 m depth. The temperature of this zone is based on the formation of chlorite and epidote. Minerals are formed
at temperatures greater than 200o
C. (see Table 2.). This zone is the reservoir zone with temperature ranging from
235-250o
C (PERTAMINA, 1995).
Alteration box plot. The data needed for this method are the geochemical of altered rocks. Petrographic data required for texture and mineralogy analysis of the altered rocks. Geochemical data should be calculated using equation 1 and 4 to calculate the Ishikawa AI and CCPI. The alteration box plot is a combination of the Ishikawa AI plotted in the horizontal axis and the CCPI plotted in the vertical axis. Least altered volcanic plot toward the center of diagram, and hydrothermal altered volcanic plot at varying positions dependent on the principal hydrothermal mineral present. The mineral end members plot along the boundaries of the box in the position marked.
In this study, geochemical analyzes performed on surface and subsurface rocks in well KMJ-49. The surface samples are needed to compare the surface rock units with subsurface lithology. The analysis has been done so that
the distribution of the surface lithology units can be correlated with subsurface lithologies as presented on the geology map (Fig. 2). The location of the surface outcrops and the well KMJ-49 can be seen in Figure 6. The results of calculation of AI and CCPI by applying Formula 1 and 4 were conducted on all samples. The results indicate the surface samples have a value ranging between 20-34 AI and CCPI ranges 63-73. The value of AI is strongly influenced by the mineralogical composition which is composed of plagioclase, pyroxene and volcanic glass as groundmass. Some phenocryst and groundmass appears to be altered into chlorite, clay minerals and iron oxides. The relationship of mineralogy and texture for surface samples seen in the relationship of AI and CPPI is shown in Fig. 6 and 7.
Subsurface samples have AI values around 15-46 and CCPI ranges 68-86. The rock samples have experienced hydrothermal alteration. Plagioclase, pyroxene and volcanic glass occuring as primary minerals have been altered into secondary minerals such as: crystobalite, quartz, calcite, anhydrite, pyrite, hematite, iron oxide, chlorite, epidote, montmorillonite, illite and illite-montmorillonite. The presence of altered minerals is affecting AI and CCPI values of each rock. Corresponding to depths, relative AI values decrease and on the other hand CCPI values increase. This increase is also reflected by the increase in Fe2O3 and MgO (see Fig. 8), and are characterized by the presence chlorite, hematite and epidote. AI and CCPI calculation results can be seen in Table 3. The relationship of textures, mineralogy, AI and CPPI is shown Fig. 8.
This study is based on the calculation using Formula 1 and 4, we obtained AI and CCPI values (see Table 3.).
Fig. 7. The relationship of texture, mineralogy, AI and CPPI of the surface samples
29
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. Yudiantor
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/Int. j. econ. env
. geol. V
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b
(
Fig. 9.
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D. F. Yudiantoro/Int. j. econ. env. geol. Vol:3(2) 21-32, 2012
The values then plotted on a simple diagram consisting of the variation between AI and CCPI axis and the variation between the AI with SiO2. This diagram is intended to determine the origin of rock types prior to alteration. Figure 10 shows the variation between the AI and the CCPI and a box that describes the distribution of rock types. The rock types are andesite/basalt, dacite and rhyolite. At the outer corner of the box is a assemblage of alteration minerals that may be present in the altered rocks. Epidote, calcite are the alteration minerals containing calcium, while chlorite and pyrite are a group of minerals that contains magnesiun and ferrum. Albit and K-feldspar are a group of minerals that contain sodium and potassium.
The resulting plot of the surface and well samples indicate that all the samples were in the box of andesite/basalt types (Fig. 9). While the results of sample plotting on SiO2 and AI variation diagram show that there are three groups of rocks: basalts (SiO2 <52%), basaltic andesite (52-55% SiO2) and andesite (SiO2> 55%). AI values of each rock groups did not show significant characteristics, each group varies around 15-46 (see Fig. 11). The basaltic andesite is shown in Fig. 11. It shows that the rock types in the group were identical to the lithology units that exposed at the surface as seen in the geological map of the study area. So the distribution of surface rock units is highly correlated with subsurface rock units. It's only at depth of 85-130 m the rock types obtained from plotting AI vs SiO2 indicate basalt-basaltic andesite, while the exposed rock at the surface around the well KMJ-49 was pyroxene andesite. It is interpreted that the formation of pyroxene andesite of Mount cakra is started by basalt interstratified with basaltic andesite and ended by deposition of pyroxene andesite. The results of plotting the CPPI vs SiO2 variation diagram explain that all of rock samples processes are caused by the activities of basalt to andesite magmatism composition (Fig. 12).
Conclusion
AI and CCPI calculation conducted on all samples result in as follows: The surface sample had a value ranging
between 20-34 for AI and CCPI range 63-73. Subsurface samples have AI values around 15-46 and CCPI ranges 68-86. All rock samples have experienced hydrothermal alteration. The subsurface samples when observed corresponding to depth indicate the AI values relatively decrease and the CCPI values increase. This increasing is also reflected by the increase of Fe2O3 and MgO associated with the presence chlorit, hematite and epidote. The alkali (Na2O and K2O) is high (as in samples 5-9) in andesitic rocks, while the lower alkali is occurred in basalt-basaltic andesite. The trending of fractionation from basalt toward andesite is shown by the increasing value of SiO2 and decreasing of CCPI.
Acknowledgement
The author extends gratitude to Akita University Japan who have given in this research facility and Pertamina Geothermal Energy for permission to publish this paper. I wish to express my appreciation to Dr. C.Prastyadi (Geological Engineering UPN Veteran Yogyakarta, Indonesia) for reading the original manuscript and offering many constructive criticisms.
Fig. 10. Variation in Ishikawa AI with CCPI content for a set of least altered volcanic at well KMJ-49.
Fig. 11. Variation in Ishikawa AI with SiO2 content for a set of least altered volcanic at well KMJ-49 (2<Na2O<5 wt%)
References
Date, J; Watanabe, Y; Saeki, Y. (1983) Zonal alteration around the fukasawa kuroko deposits, akita prefecture, northern Japan: Economic Geology Monograph, 5, p.365-386.
Eastoe, C.J; Solomon, M; Walshe, J.L. (1987) District-scale alteration associated with massive sulfide deposits in the mount read volcanics, western
Tasmania. Economic Geology, 82, p.1239-1258
Herrmann, W; Hill, A.P. (2001) The origin of chloride-tremaolite-carbonate rocks associated with the thalanga volcanic-hosted massive sulfide deposit,
north Queenland, Australia. Economic Geology, 96,
p.1149-1173.
Ishikawa, Y; Sawaguchi, T; Iwaya, S; Horiuchi, M. (1976) Delineation of prospecting targets for kuroko deposits based on models of volcanism of underlying dacite
and alteration halos. Minning Geology, 26,
p.103-117.
Kamah, Y; Tavip, D; Agus, A.Z. (2003) Penanggulangan problem geologi dalam operasi pemboran sumur di blok timur area geothermal kamojang jawa barat
Indonesia. Proceeding 6Th
Indonesian Geothermal Association, p.175-184.
Kamah, Y.M; Dwikorianto, T; Zuhro, A.A; Sunaryo, D; Hasibuan, A. (2005) The productive feed zones indetified based on spinner data and application in the reservoir potensial review of kamojang
geothermal area, Indonesia, Proceeding World
Geothermal Congress Antalya, Turkey, p.1-6. Large, R.R. (1992) Australian volcanic-hosted massive sulfide deposits: Features, styles, and genetic models. Economic Geology, 87, p.471-510.
Large, R.R; Allen, R.L; Blake, M.D; Hermann, W. (2001) Hydrothermal alteration and volatile element halos for the rosebery k lens volcanic-hosted massive
sulfide deposits, western Tasmania. Economic
Geology, 96, p.1055-1072.
Large, R.R; Gemmell, J.B; Paulick, H. (2001) The alteration box plot: A simple approach to understanding the relationship between alteration mineralogy and lithogeochemistry associated with volcanic-hosted massive sulfide deposits. Economic Geology, 96, p.957-971.
Lentz, D.R. (1996) Recent advances in lithogeochemical exploration for massive sulfide deposits in volcanic-sedimentary environments: petrogenetic, chemostratigraphic an alteration aspects with examples from the bathurst camp, new brunswick: new bruswick departement of natural resources and
energy. Mineral and energy division mineral
resources report, 96-1, p.73-119.
Lydon, J.W. (1988) Some observation on the mineralogy
and chemical zonation pattern of volcanogenic sulphide deposits of Cyprus. Geological Survey of Canada Paper, 84-1A, p.611-616.
Paulic, H; Herrmamm, W; Gemmel, J.B. (2001) Alteration of felsic volcanics hosting the talanga massive sulfide deposit, north queensland australia, Australia. Geochemical Proximity Indicators to Ore: Economic Geology, 96, p.1175-1200.
PERTAMINA. (1995) Evaluasi kelayakan pengembangan area panasbumi kamojang, laporan internal PERTAMINA divisi panasbumi direktorat eksplorasi
dan produksi, Tim Pokja Kamojang, 53 pp.
Purba, S. (1994) Hydrothermal alteration of core and cutting samples from wells KMJ-48 and 53 Kamojang. Geothermal Field West Java Indonesia, pp. 58.
Robert, D; Raharso, R; Bastaman, S. (1983) Exploration and development of the kamojang. Geothermal Field, proc. IPA. p. 171 190.
Robert, D. (1987) Geological study of the western part o f t h e k a w a h k a m o j a n g g e o t h e r m a l , PERTAMINA/BEICIP report, 89 pp.
Robert, D. (1988) Subsurface study on the optimalisation of the development of the kamojang geothermal field, BEICIP/ GEOSERVICES, PERTAMINA Divisi Panasbumi (Internal Report), 47 pp.
Sangster, D.F. (1972) Precambrium volcanogenic massive sulfide deposits in Canada: A review: Geological Survey of Canada Paper 72-22, 44 p.
Schardt, C; Cooke, D.R; Gemmell, J.B; Large, R.R. (2001) Geochemical modeling of the zoned footwall alteration pipe, hellyer volcanic-hosted massive sulfide deposits, westrn Tasmania, Australia. Economic Geology, 96, p.1037-1947.
Sudarman, S. (1983) Geophysical Studies of the Kamojang and Darajat Geothermal Field (Java), Thesis Master Degree of University of Auckland, 157 pp. Sudarman, S; Hochstein, M.P. (1983) Geophysical structure of the Kamojang gothermal field (Java), Proceeding of 5th
NZ Geothermal Workshop, p. 225 230.
Sudarman, S.M; Boedihardi, K; Pastuti, B. (1995) Kamojang geothermal field 10 year operation
experience, Proceeding of WGC, p.1773-1777.
Utami, P; Browne, P.R.L. (1999) Subsurface hydrothermal alteration in the Kamojang geothermal field west
java indonesia, Proceeding of 24th
