Geochemical and petrogenetic features of schistose rocks of the Okemesi fold belt, Southwestern Nigeria
Geokemične in petrogenetske značilnosti skrilavih kamnin v sistemu gub Okemesi, jugozahodna Nigerija
Olugbenga A. Okunlola & Richardson E. Okoroafor
University of Ibadan, Department of Geology, Ibadan, Nigeria Corresponding author. E-mail: o.okunlola@mailui.edu.ng
Received: January 13, 2009	Accepted: March 18, 2009
Abstract: Schist belts form a dominant component of the Precambrian basement complex of Nigeria. This study of schistose rocks around the Okemesi fold belt, Ife-Ilesha schist belt therefore, is with a view to evaluate their compositional features and petrogenetic affinities and to contribute further to the understanding of the geodynamic evolution of Nigeria's Schist belts.
Three lithologic varieties, namely quartzite, quartz schist and biotite muscovite schist are revealed from systematic mapping and petro-graphic examinations. Whole rock analytical results of major, trace and rare earth elements of fifteen samples using ICP mass spectrometer method show that the rock units are comparable to those of post Archean pelitic-supracrustal rocks. Variation plots involving Na2O3, Al2O3 and K2O on one hand and TiO2 and SiO2 on the other hand reveal arkosic sedimentary progenitors for the rocks. In addition, La/ Th and Th/U ratio suggest that the rocks especially biotite schist is associated with post Archean recycled Upper Crustal sources while Chondrite normalized rare earth signatures of samples further indicate low grade post Archean terrigenous sedimentation of rocks derived from possible mixture of granite- tonalities. Relatively intense weathering and maturity of source rocks is revealed from calculated values of Index of alteration (CIA) and Index of Compositional Variability (ICV). The study further elucidates the possibility of the rocks evolving in a rifted environment of rapid subsidence, followed by closure which led to contemporaneous deformation of the sediments
Izvleček: Metamorfni skrilavci so prevladujoča kamnina v predkambrij-skem metamorfnem masivu Nigerije. Namen raziskave je določiti sestavo ter nastanek skrilavih kamnin Okemesi pasu, in sicer Ife-Ilesha pasu metamorfnih skrilavcev. Rezultati bodo prispevali k razumevanju geodinamičnega razvoja nigerijskih metamorfnih skrilavcev.
S sistematičnim geološkim kartiranjem in petrografskimi raziskavami smo ugotovili tri litiološke različke - kvarcit, kremenovi skrilavci in biotitno muskovitni blestniki. Z metodo ICP masno spektroskopijo smo določili vsebnost glavnih in slednih prvin ter prvin redkih zemelj v petnajstih vzorcih. Analize so pokazale, da so raziskovani tipi kamnin primerljivi s po-arhajskimi pelitskimi kamninami zgornje skorje. Tako variacijski diagrami Na2O3, Al2O3 in K2O kot tudi TiO2 in SiO2 potrjujejo, da je bila izvirna kamnina sedimentna - ar-koza.
Razmerji La/Th in Th/U nakazujeta, da so kamnine, zlasti biotitni blestnik, nastale iz po-arhajske reciklirane zgornje skorje. Iz vzorcev hondritsko normaliziranih REE sklepamo, da je bila prvotna kamnina nizko metamorfoziranih arhajskih terigenih sedimentnih kamnin mešanica granitov in tonalitov. Izračunane vrednosti indeksa preperevanja (CIA) in indeksa spremenljivosti sestave (ICV) kažejo na relativno močno preperevanje ter zrelost izvirnih kamnin. V študiji podajamo možnost nastanka kamnin v okolju hitrega pogre-zanja razpornega bazena, ki mu je sledilo zapiranje; to je povzročilo sočasno deformacijo sedimentov.
Key words: schist, archean, sedimentary, rifted, compositional
Ključne besede: metamorfni skrilavci, kvarcit, arhaik, sedimentne kamnine, zgornja skorja
Introduction
Schistose rocks which occur in defined belts are known to be a dominant feature and constitute a distinct component of the western half of the Precambrian Basement Complex of Nigeria. This basement complex itself, apart from the schist belt, is made of
the Gneiss- migmatite complex and the Pan African Older Granite rocks. The schist belts are made up of mainly low-medium grade metasediments which are usually associated with minor assemblages of mafic-ultramafic rocks, iron deposits and carbonates (Muotoh et al., 1988; Okunlola, 2001).
These northerly trending schist belts occur prominently west of 80 Meridian (Oyawoye 1964, 1972; Mccurry , 1976). However, it is now known that some extend eastwards of this meridian (Ajibade , 1976; Emeronye , 1988; Eneh et al., 1989; Ekwueme and Shing, 1987). They exhibit distinct penological and structural features. The belts in the southwest include the Iseyin-Oyan, Igarra, Egbe-Isanlu and Ife-Ilesha schist belts (Rahaman , 1976; Odeyemi , 1977; Elueze, 1981; Annor et al., 1996). The Lokoja-Jakura, Toto-Gadabuike belts (Muotoh et al., 1988; Elueze, 1981; Okunlola, 2001) while the Obudu schist belt is the recently highlighted southeastern belt (Ekwueme & Shing, 1987). So far, there is no complete agreement on delineation, geological nomenclature and geodynamic setting of this major rock unit of the Nigerian Precambrian basement Complex. In this study attempts are made to elucidate the geochemical and petrogenetic features of the schistose rocks around the Okemesi fold belt area, which is a part of the Ife- Ilesha schist belt. The latter has one of the most complex lithologi-cal and structural frameworks amongst the Nigeria's metasedimentary belts (Olobaniyi , 2003). The present study, it is hoped will assist in understanding the evolution of this major rock unit of the Precambrian of Nigeria.
Materials and methods
The study involves systematic geological mapping on a scale of 1 : 50 000 collection and thin section study of 15 fresh representative samples of all the lithological units mapped. Four samples each were collected from the quartz schist and biotite muscovite schist and 7 from the quartzite. Variation in sample numbers is largely due to availability of fresh unweathered and uncontaminated samples. For geochemical investigations, collected samples were dried at 60 oC, crushed, pulverized and sieved to -80 mesh. A 0.2 g samples aliquot was weighed into a graphite crucible and mixed with 1.5 g of LiBO2/LiB407 The sample charge was heated in a muffle furnace for 30 min at 980 oC. The cooled bead is dissolved in 100 mL of 5 % HNO3 (ACS grade nitric acid in de-mineralized water). An aliquot of the solution was poured into a propylene test tube. Calibration standards and verification standards are included in the sample sequence. Sample solutions are aspirated into an ICP mass spectrometer (Perkin-Elmer Elan 9000) for the determination of major, minor and rare earth elements at the Acme Laboratories in Vancouver Canada. Quality control protocol incorporates a sample preparation blank (G1) as the first sample in the proce-
dure which is carried through all stages of preparation to analysis. Also, the procedure incorporates a pulp duplicate to monitor analytical precision, a reagent blank to measure background and aliquots of in-house reference material STD SO-18.
structure comprising massive quartz-ite, quartz schist, and mica schist with subordinate gneisses and amphibolites (Figure 1). These metasedimentary assemblages has been hitherto referred to as the Effon psammite formation (De Swardt, 1953; Hubbard, et al., 1975).
Results and discussion
Lithological relationship and petrography
The Okemesi Fold Belt lies between Latitudes 70 45' and 70 52' and Longitudes 40 54' and 40 50' E and covers an area of 132.25 km2. It has an antiformal
The quartzite samples are mostly whitish in color but some ferruginized varieties display reddish bands. They are medium to fine-grained, steeply dipping, with an average dip of 540 E. They consist mainly of quartz which occurs as irregular fine to medium grained crystals with interlocking grains of muscovite. In thin section, the quartz
Figure 1. The Geological map of Okemesi fold belt.
grains are colorless to grey in transmitted light. The quartz schist which forms the innermost parts of the Okemesi anticline, occur as low-lying outcrops. They are fine to medium-grained, display incipient schistosity and contain quartz, microcline, muscovite with accessory hematite and zircon. Quartz occurs as randomly oriented crystals. Two generations are evident. The first one is coarser grained, usually anhe-dral and elongated parallel to the fabric. Some grains exhibit wavy extinction. The finer grained variety occurs as localized granoblastic aggregates and show uniform extinction. This variety may likely be of secondary origin. Microcline which is present in minor amounts as crosshatched twinned elongate fine blasts are located sometimes in intergranular spaces of the interlocking quartz blasts.
The biotite- muscovite schist also occurs in lowland areas between the quartzite ridges and trend generally in the NNE-SSW direction. The foliation on the outcrop is defined by mica streaks, particularly biotite. The schist is generally coarse-grained and contains mainly muscovite, biotite and minor quartz. In thin section, quartz occurs as coarse-grained, stretched, and white to greyish anhedral blasts. Biotite occurs as light brown leaflet sometimes slender and prismatic with occa-
sional stumpy laths and is pleochroic from light brown to reddish brown. Muscovite is subhedral, showing alignment in the foliation plane (Figure 2). Plagioclase is of oligoclase-andesine composition, mostly colourless but in the absence of twinning it is often distinguished from quartz by the alteration to sausurite. Euhedral to subhedral garnet is predominantly almandine with minor amounts of spessartine and grossularite. They sometimes exhibit poikiloblastic texture and are characterized by inclusion of fine quartz and some mica. The schistose rocks occur in association with banded gneiss and amphibolites which occupy mainly the outer portions of the anticline and are more prominent in the eastern side.
Figure 2. Photomicrograph of biotite-muscovite schist in transmitted light showing Quartz (Q), Biotite (B), and Muscovite (Mu)
The banded gneiss consists of alternating bands of felsic minerals notably
plagioclase feldspars and quartz, and the dark bands consisting of biotite and hornblende. Quartz is present as coarsegrained randomly oriented crystals. The amphibolite which is mostly low lying is laminated in places with leucocratic bands of plagioclase and quartz. Hornblende is the main mineral with minor quartz and plagioclase. Quartz is het-erogranoblastic, colourless in transmitted light and in some parts, fractured. The hornblende crystals are pleochroic from brown to light green.
Table 1. Major Element Oxides (w/%) results of schistose rocks from Okemesi
	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
SiO2	88.91	81.11	83.32	84.17	65.31	65.42	65.38	96.97	96.64	94.18	94.10	94.21	96.61	94.21	94.67
Al2O3	6.52	9.37	8.51	8.21	13.55	13.81	13.82	0.79	1.17	4.11	2.34	1.98	2.31	2.62	2.11
Fe203	0.68	1.29	1.21	1.63	6.30	6.41	6.42	1.22	0.74	0.38	2.1	2.45	0.52	2.41	1.56
MnO	0.0 11	0.02	0.02	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	0.01	<0.01
MgO	0.08	0.75	0.71	0.80	2.97	2.64	2.61	0.07	0.12	0.09	0.09	0.06	0.11	0.12	0.11
CaO	0.11	0.410	0.12	0.11	0.11	0.12	0.13	0.12	0.14	0.10	0.09	0.12	0.10	0.11	0.13
Na2O	0.14	0.68	0.61	0.58	0.14	0.13	0.14	0.01	0.02	0.01	0.04	0.03	0.02	0.02	0.03
KO	1.76	3.89	3.11	2.64	1.76	2.1	2.5	0.04	0.21	0.07	0.08	0.06	0.05	0.04	0.07
P2O5	0.10	0.22	0.17	0.11	0.10	0.20	0.21	0.03	0.03	0.02	0.03	0.02	0.01	0.01	0.03
Ti02	0.24	0.23	0.23	0.22	0.24	0.31	0.32	0.05	0.07	0.20	0.16	0.07	0.08	0.07	0.08
C^2O3	0.011	0.012	0.012	0.013	0.011	0.021	0.019	0.046	0.048	0.017	0.020	0.043	0.021	0.042	0.045
LOI	1.2	1.8	1.2	1.3	1.2	1.3	1.3	0.7	0.8	0.8	1.0	1.0	1.0	0.9	1.0
Total	99.75	99.79	99.22	99.99	99.75	99.86	99.81	100.05	99.99	99.98	99.97	99.95	100.83	100.6	99.83
1, 2, 3 and 4 = Quartz Schist
5, 6 and 7 = Biotite-muscovite Schist
8-15 = Quartzite
Geochemical features
From the results of the major oxide data (w/%), trace and rare earth element (pg/g) composition presented in Tables 1 and 2, the Okemesi metasedi-mentary rocks are generally siliceous, (w(SiO2) > 65 %) with quartzite being chemically similar to quart-sandstones (Blatt, et. al., 1972). These values are also similar to those for the Jebba quartzite and micaceous quartzite, central Nigeria (Okonkwo , 2006).
Table 2. Showing Trace Elements (^g/g) analytical results of rocks from Okemesi
	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Sc	13	4	7	6	2	6	4	nd	1	1	1	1	1	nd	1
Be	2	1	2	2	3	2	3	nd	4	2	1	4	2	1	2
V	63	nd	61	61	21	45	40	nd	nd	nd	8	nd	nd	8	8
Ba	93	911	902	880	968	942	902	85	15	60	42	65	62	59	71
Sr	325	201	202	362	64	58	60	12	27	46	32	40	55	31	28
Y	44	47	45	42	33	36	38	32	16	32	22	18	5	10	21
Zr	630	133	589	579	733	829	812	211	318	93	242	200	195	181	262
Co	11	nd	10	10	3	4	4	1	1	1	1	1	1	1	1
Ni	25	20	24	20	20	21	22	20	20	3	4	3	3	3	3
Cu	29	4	4	28	2	3	3.8	6	3	3	4	4	5	4	3
Zn	88	2	81	71	14	30	28	5	5	4	4	5	4	4	3
Ga	20	7	11	10	7	11	10	1	4	4	3	5	5	5	4
As	nd	nd	nd	nd	nd	nd	nd	5	5	nd	nd	3	nd	nd	nd
Rb	127	76	108	109	118	120	119	31	26	35	25	14	31	21	21
Nb	21	11	20	20	6	6.5	6	5	4	5	5	2	3	4	5
Sn	8	11	7	8	2	4	4	1	1	1	1	1	1	1	2
Cs	2	2	2	2	4.5	2	2	nd	2	3	5	6	6	5	4.
Au	nd	nd	nd	nd	1	1	1	nd	nd	nd	nd	nd	nd	nd	nd
Rb/Sr	0.39	0.38	0.54	0.30	1.84	1.98	1.98	2.55	0.96	0.75	0.78	0.34	0.57	0.67	0.76
Sr/Ba	0.35	0.22	0.22	0.41	0.07	0.07	0.07	0.15	1.85	0.78	0.75	0.63	0.89	0.52	0.39
1, 2, 3 and 4 = Quartz Schist
5, 6 and 7 = Biotite-muscovite Schist
8-15 = Quartzite
is also noticeable in the mean Fe2O3 content of the metasediments where the values are less than 7 %. Mean MnO content is generally low (< 0.15 %) in the entire samples. These trends prob-
Average Al2O3 content is lowest in the quartzites (1.93 %). The biotite muscovite schist has a much higher average value of Al2O3 (13.92 %) than the quartz schist (8.15 %). The same trend
ably denote an increase in chemically unstable grains (lithic components) with decrease in quartz content. The values are however within the range for metasediments (Weaver, 1989). Average MgO, CaO, and Na2O values are generally less than 0.60 % except for the mica schists that have a mean MgO value of 2.74 %. Mean K2O content is highest in the quartz schist with the quartzites having the lowest value of 0.57 %. The depleted MnO, Na2O may suggest paucity of movement of metamorphic remobilized fluids during the Pan African or earlier events. Some of Nigeria's schist belt especially the shear zones host auriferous quartz that are presumed to be formed by metamorphic dewatering of the country rocks during the Pan African tectonic phase. (Olobaniyi , 2003) This result therefore, explains the paucity of auriferous veins as noted in an earlier study around this sector of the Ife-Ile-sha Schist belt compared to the more mineralized eastern parts about 80 km from this study area (Elueze , 1992) . The values are still within those for metasedimentary rocks (Brown et al., 1979) and comparable to that of Scottish metapelites (Okonkwo , 1992), Ig-arra quartz mica schist (Okeke & Meju , 1985) and Burum Marble (Okunlola, 2001). Average TiO2 is highest in the biotite muscovite schist, 0.21 % for the quartz schist and 0.29 % for the mica schist, whereas the quartzite has a mean
TiO2 value 0.10 %. Mean Cr2O3 content is generally low in all the samples of both the schists (0.012-0.017 %) and the quartzite (0.035 %). Compared with the post Archean metasediments, the Okemesi rocks are depleted in CaO and Al2O3, while they are richer in K2O when compared with the Archean mud-stone (Taylor & Mclennan, 1985). Also a seemingly positive trend is noticed between the Al2O3 and TiO2 values in the biotite muscovite schist, suggesting that TiO2 may have been held in the clay mineral lattices. (Figures 3 and 4).This is, unlike the indiscernible or scattered trend in the quartzite and the quartz schist, suggesting that both oxides are contained in the heavy mineral phases. Conversely Zr and Nb in the quartz schist shows a positive trend and this suggest their containment in the heavy mineral phases (Figure 5).
Figure 3. TiO2 versus Al2O3 plot of rocks from Okemesi
1HX»-		*tr	
	0		
	;	thAtM	
IÛU -		f	
I			
Siw-	s e a DO		
N ID -			
	o\	TiiO r%l'	<A
		
IW0> -		J] Î-H ■ F IMllM
IW) -	*	t i'
1 ft m-		
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		1 st m 4, h »
Figure 4. Zr versus TiO2 plot of rocks from Figure 5. Zr versus Nb plot of rocks from
Okemesi
Okemesi
Ba, Sr, Rb and Zr concentrations are more enhanced in the quartz schist than in the quartzite (Table 2) but are well within the range for supracrustal rocks (Brown et al., 1979; Babcock et al, 1979). In particular, the high Zr content may reflect the presence of detrital zircon in the rocks (Elueze , 1981). Zn, Cu and Co content (pg/g) is generally low. The schistose rocks are generally low in Sr/Ba ratios (< 0.4 %). However, Rb/ Sr ratio (> 0.4 %) is typical for pelitic metasediments (Van De Kamp, 1968).
The petrogenetic character of the rocks as established on the Na2O/Al2O3 versus K2O/Al2O2 diagram (Garrels & Mackenzie, 1971) (Figure 6) shows that the rocks are largely of sedimentary origin. In the MgO-CaO-Al2O3 diagram (Figure 10) (Leyleroup, et al., 1977) the samples plot outside the magmatic field which also supports the
sedimentary antecedent of the rocks. These features are similar to those for Ilesha metasediments (Elueze , 1981), Birnin Gwari schist (Ajibade, 1980) and Jebba schists (Okonkwo & Win -Chester, 1996; Okonkwo , 2006). However, the Na2O versus K2O plot (Petti -john , 1975) (Figure 7) shows possible arkosic affinity of the metasediments, but the discrimination function diagram (Roser & Korsch ,1988) (Figure 8) shows that the samples are generally of quartzose sedimentary provenance with the samples plotting deep into the quartzose sedimentary field. The TiO2-K2O-P2O5 plot (Pearce et al., 1975) (Figure 9) confirms the continental nature of the sediments. On the Al2O3-CN-K2O plot, (Figure 10) the biotite schists and the quartzite plot close to the illite and kaolinite fields while the quartz schist plot close to the average shale. The relatively high content of Ba
in contrast to Rb indicates the contribution of felsic components since Ba indicates K-feldspar-rich source rocks. (Okonkwo , 1992; Okonkwo & Win -Chester , 1998) In addition, Taylor & Mclennan, (1985) have indicated the importance of such immobile trace elements as Th and La in provenance de-
terminations of pelitic metasediments because they often reflect those of source rocks. The Th content of Okem-esi metasediments (1.4-43.3 pg/g) is comparable to those derived from granitic composition. Also most of the samples analysed have low La/Th and Th/U especially those for the biotite
Figure 6. Na2O/Al2O3 against K2O/Al2O3 plot for the Okemesi metasediments (Gar-rells & Mackenzie , 1971)
Figure 8. Discrimination Function Diagram of rocks from Okemesi (Roser & Korsch, 1988)
Figure 7. Na20 versus K20 plot of rocks Figure 9. Ti02-K20-P205 plot of rocks from Okemesi (Pettijohn, 1975)	from Okemesi (PEARCE et al., 1975)
Figure 10. Al2O3-CN-K2O plot for the Okemesi rocks
muscovite schists. This feature is normally associated with post Archean recycled upper crust sources (Leyleroup et. al., 1977; Taylor et. al., 1986).
The rock samples generally exhibit REE values and patterns typical of low grade Post Archean terrigenous sediments with variable enriched steep LREE and almost flat HREE with no discernible Eu anomaly. (Table 3, Figure 11). La/Yb ratio is also high, resembling the Yellowknife and Pil-bara metasediments (Mclennan et al., 1983). These features suggest sediment derivation from a source dominated by felsic igneous rocks (Mclennan & Taylor , 1984). Taylor and co workers, (1986) have also suggested that sediments with steep LREE enrichments and low Al22O3/Na2O ratio point to derivation from a possible mixture of granite-tonalite rocks to produce the sedimentary protolith.
Figure 11. Chondrite normalised REE plot of the Okemesi rocks
The results of the Chemical Index of Alteration (CIA) (Nesbitt & Young 1982; Okunlola, 2003) reveal average values of 69.7 %, 85.9 % and 91.2 % for the quartz schist, mica schist and quartzite (Table 4). These values point to relatively intense chemical weathering of the source rocks. The Index of Compositional Variability (ICV) (Cox & Lowe, 1995) which measures the abundance of alumina relative to other constituents of the rock, except SiO2 show that the quartz schist, biotite-mu-covite schist and the quartzite have an average ICV values of 0.68, 0.85 and 0.83 respectively (Table 4). Compo-sitionally immature pelitic rocks have high ICV, whereas mature pelititc rocks with very little non silicates or those rich in kaolinite group clay minerals possess low values (< 0.6) (Elueze & Okunlola, 2003). The calculated ICV value for the quartz schist (0.68) shows the matured nature of the sedimen-
tary protolith prior to metamorphism. Mature to moderately mature pelitic metasediments are characteristic of relatively stable cratonic environments (Weaver, 1989). This may be marked by sediment recycling or moderate to very intense chemical weathering of first cycle material (Bershad , 1966).
In terms of the geodynamic evolution of the rocks in the study area, The Ife-Ilesha schist belt has been thought by earlier workers to be an ensialic basin in an environment of thin and attenuated Crust (Ajibade , 1976; Elueze , 1992; Annor , et.al., 1996). Therefore, the occurrence of sub greywacke rocks in the study area as evidenced, suggests a rapidly subsiding depocenter basin, or that there existed much difference in topographic elevation between the sediment source and depocenter. However, since typical deep water sediments and proximal distal-facies variations are absent, there is the possibility that only a moderate depth and width was attained in the basin in the absence of the development of a fully mature ocean. The rapid subsidence of the basin was accompanied contemporaneously with tectonic instability resulting in antiformal deformation and multidirectional fracturing. This may have aided the rapid removal of the sediments before deep weathering and mineralogical maturity was attained. This activity probably accounts for the shallowness of the depth of the basin. Similar characteristics
have been noted for the Isanlu schist belt, central Nigeria (Olobaniyi , 2003). The Nigeria's schist belt is believed to have evolved as a result of an initial continental extensional stage culminating in rift openings and sedimentation with contemporaneous magmatism in the formed basins. These processes were followed by basin closure which led to the deformation of sediments. (Ajibade, et.al., 1987; Elueze, 1992). As seen in this study from petrographic and chemical signature, the Okemesi schistose rocks, which outcrops in the eastern part of the Ife- llesha schist belt,have most probably evolved in a rifted environment of rapid subsidence.
Conclusions
Systematic geological mapping, petro-graphic and geochemical evaluation of schistose rocks around the Okemesi fold belt show that the metasedimen-tary assemblages which form the inner portion of the Okemesi anticline are continental post Archean supracrust-als. The sedimentary protolith prior to metamorphism and tectonism have had arkosic affinity and may have also been derived from original source rocks rich in felsic components. However, the discriminant plot of Roser & Korsch (1988), suggests contribution from a quartzose sedimentary provenance. Calculations of the Chemical Index of
Alteration (CIA) and Index of Compositional Variability (ICV) show that the schistose rocks are metamorphosed from intensely weathered and mature sediments. Furthermore, the REE signatures confirm the possible contribution of material to the sedimentary protolith from a mixture of granite and tonalite rocks. The rocks are believed to have evolved in a rifted environment accompanied by rapid subsidence.
Acknowledgement
This study has benefited from the assistances of numerous friends and colleagues. The staff of ACME laboratories, Vancouver Canada are specially appreciated for their assistance during the geochemical analysis.
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