Investigating Geochemical Patterns of Major and Trace El-ements in Granitic Rocks of the Oulmes Region, Central Morocco: Instrumental Neutron Activation Analysis (INAA)

. In this study, we used the instrumental neutron activation analysis technique (INAA) for analysis of granite samples from four locations in Oulmes region of central Morocco. In order to investigate the geochemical behavior of both major and trace elements in granite rocks from study area. The four samples almost accurately reflect the geochemical variety and heterogeneity of the formations were taken from distinct outcrops. The aim of study was to characterize the mineralization patterns of granitic rocks, their sources and basic composition. The results highlight the importance of nuclear techniques in geochemical investigations and provide some insights into the geochemical processes that shaped these rocks.


Introduction
Granitic rocks are essential elements of the Earth's crust and have a major influence on the geological and mineralogical properties of diverse geographical regions all over the world.Oulmes region, which lies in the heart of Morocco, is well known for its variety of granitic formations, which show variances in their geochemical behavior and mineralization potential.Understanding the petro-genesis and the geological development of these granitic rocks requires an understanding of the geochemical behavior of major and trace elements in side them.To examine the geochemical behavior of major and trace elements in granites from various outcrops in the Oulmes region, we use the instrumental neutron activation analysis (INAA) approach in this study.Nuclear analytical methods have been successfully applied for the determination of a great variety of elements in environmental, biological and geological samples [1].Neutron activation analysis techniques have been improved and have become an excellent tool for such purposes actually different techniques could be used for estimating the trace minor and major elements of these environmental samples, which are considered as complex samples.The major advantages of NAA are(a) the relative freedom from matrix effects and interferences,(b)high accuracy and (c) very low zero blank contributions.Because nuclear reactions and decay processes are virtually unaffected by chemical and physical structures of the material during and after irradiation, the composition of the matrix has little influence on the induced activity put this technique in the forefront [2].Four typical samples were gathered for this study from various granitic outcrops in the Oulmes area.The geochemical diversity and variability found in the granitic formations were thoroughly captured in the samples used.We want to examine the distribution and behavior of major elements like Aluminum (Al), Iron (Fe), Potassium (K), and trace elements like Uranium (U),Thorium (Th).The objective of the study is to characterize the mineralization patterns, source, and elemental composition of the granitic rocks in the Oulmes region.The results of this investigation will offer insightful knowledge about the geochemical behavior of both major and trace elements in the granitic rocks of the Oulmes region.Furthermore, the use of INAA as a potent analytical approach highlights the significance of nuclear methods in geochemical studies and highlights their crucial role in understanding the intricate (complicated) geochemical processes of granitic rocks.Using the instrumental neutron activation analysis (INAA) method, this paper provides a thorough examination into the geochemical behavior of major and trace elements in granitic rocks of the Oulmes region.

Sample collection and preparation
Four granite rock samples were collected from four locations at Oulmes region,see figure 1.The samples we collected, we crushed them in an agate mortar to obtain a fine and homogeneous powder, and then stored in polyethylene bags until analysis.

Instrumentation
The granitic samples underwent irradiation at the Neutron Activation Analysis (NAA) laboratory, which is located at the National Centre for Energy, Sciences, and Nuclear Techniques  (CNESTEN).The irradiation process took place within the TRIGA MARK II research reactor, which served as the neutron source for this analysis.The samples were carefully exposed to a controlled neutron flux within the reactor.If we want to be more precise, the irradiation process was carried out using the pneumatic transfer system (PTS) and the Rotary specimen rack (RSR) with a thermal neutron flux of 5.10 12 n/cm 2 .sand 2.10 13 n/cm 2 .srespectively .The concentrations of the elements in the sample were determined using the neutron activation analysis technique.So, based on the half-lives of the elements being measured, two types of irradiation were carried out: those with a short half-life were irradiated for 30 s, while those with a long half-life were irradiated for 5 h.Each sample was prepared with a flux monitor (an Al/Au wire containing confirmed 0.1% Au) for the brief irradiations.A capsule made of high-purity polyethylene was filled with 200-280 mg of each sample before being heat-sealed.After being secured in a polyethylene bunny, the sample and flux monitor were moved to the reactor core using a pneumatic transfer system that makes it possible to irradiate samples one at a time.As For the long irradiations, the samples were sealed in pure polyethylene irradiation vials and placed in a polyethylene rabbit together with a comparator to be used as a neutron flux monitor.The k0-IAEA software was used to calculate element concentrations.A standard reference material was used for quality control, mainly to assess the precision of the technique being employed, and the values were found to be in acceptable agreement with the certified value.A high-purity germanium detector (HP-Ge) with a relative efficiency of 30% was used for the measurements.Gamma vision software was used to analyze light peak data.The cooling time for the brief irradiations was 6 m.The lengthy irradiations underwent two measurements.First, measurement was done for 14 m for the medium half-life isotopes (La and Sm) after 7 days of cooling time, and for 8 h for the long half-life isotopes (Nd, Ce, Eu, Tb, Yb, and Lu) after 26 weeks of cooling time, see tab 1.The element concentrations were calculated using the k0-IAEA software.The values were found to be in acceptable agreement with the certified value after using a standard reference material for quality control, primarily to evaluate the accuracy of the technique being applied .

Results and discussion
In this study, the k0-IAEA tool was used to calculate the all elements contents in 4 granite samples taken from Oulmes region.The degree of convergence between the results of this approach in this work and the certified concentrations of NIST Standard Reference Material 2586 (NIST SRM 2586) was used to assess the correct Table 2 displays the average element concentrations, relative standard deviation (RSD%), and relative difference between the analytical approach and the reference value that were obtained from three replicates on SMR2586.The ratio between the difference between the certified and INAA averages serves Where X1 is the obtained value by instrumental neutron activation analysis (INAA) and X2 is the certified or the recommended value.RSD (%) relative standard deviation.
Results obtained in the granite of Oulmes region are presented in Table 3.The distribution study of major and trace elements concentrations was also discussed.
Remark: Major elements (Al, Fe, Mn, Na, K, Mg and Ti) are in % while trace elements are in ppm.

Pearson Correlation
In our research, we employed the Pearson correlation coefficient as a pivotal statistical tool to delve into two aspects.Firstly, we utilized this coefficient to meticulously investigate the intricate behavior of major elements within the intricate composition of granite.Our aim was to gain a profound understanding of the dynamic interplay and patterns that govern the distribution and interactions among these essential constituents.Secondly, our comprehensive analysis extended to examining the nuanced connections between major and trace elements present in our diverse set of samples, all that by identifying any linear relationships between these elements.

The correlation between the major elements
Table 4 below represents a comprehensive depiction of the correlation existing among the principal elements can be observed.This data reveals a pronounced and robust positive correlation among all the various oxides.which can be attributed to their inherently analogous chemical properties and their shared origin in the natural environment.These correlations between the oxides exhibit substantial strength, with correlation coefficients reaching an impressive maximum value of 0.99.However, it's noteworthy thatK 2 O, unlike its counterparts,

The correlation between the major elements and trace elements
The correlation between the major and trace elements can be utilized to categorize and distinguish between various varieties of granite, as well as the mineral assemblages and fractionation processes that occurred during the crystallization of granite [3].Tables 5,6 and 7shows the correlation between elements.There is a significant positive correlation observed for almost all elements from 0.062 to 0.998.Nd and V showed a strong correlation with Na, Al, Ti, Ca, Fe and Mg while Zn showed a good correlation with Ti, Ca and Fe.Co showed a strong correlation with Al, Ti, Ca, Fe and Mg.Cs showed a strong correlation with Na and Al.While Hf showed a good correlation only with Ca and La with Fe and the Ce with K but the U showed a significant negative correlation with K.The rest of the trace elements did not show any significant correlations with any major element.

Principal component analysis PCA
The behavior of major and trace elements during the evolution of magmas varies according to their affinity for the crystalline and liquid phases.The partition coefficients of trace elements between the different minerals constituent the rock and liquids differ significantly.Certain elements or groups of elements can be used to identify the minerals involved in magmatic processes [3].
To determine possible relationships between major and trace elements in Oulmes granite, a PCA was carried out with the Pearson coefficient.The program used in this work is the XLSTAT.Our objectives were to obtain different groups of elements according to their correlation coefficients and to identify the chemical elements characteristics of samples taken from various outcrops in the Oulmes region.

The AFM diagram
Granite types serve as significant markers of the Earth's geological past since they are inextricably tied to geodynamic conditions.Granite is formed as a result of tectonic processes such subduction zones, continental collisions, and extensional environments.Geologists can
From the AFM diagram in Figure 3 we can see that all our samples belong to the Calcalkaline type, so it comfirmed the nature calco-alkaline of all samples.According to Barbarin [6] , our granite samples belong to the ACG and KCG groups so that ACG IS THE Amphibole Calc-alkaline granites and KCG is Potassic Calc-alkaline Granites.Which can form at any time in an orogenic phase (from subduction to the post-collision period) so those groups are often associated with subduction zones.

Conclusion
In this article, our work first focused on the implications for on involving the instrumental of neutron activation in geochemical studies.On the other hand, to study the distribution of major and trace elements in order to characterize the geochemical background of the Oulmes granite, by studying the behavior of major and trace elements.Using neutron activation analysis on the Oulmes granite, we came to the conclusion that this granite is a calco-alkaline rock, which was confirmed by the low T iO 2 content (≪ 1% for all the granites studied) and relatively high Al 2 O 3 contents also by the AFM diagram.It crystallized in the last partial crystallization phase, because a group of rare earth elements is depleted, and it shows through the anomalies in the normalization of chondrite spectras.

Figure 1 .
Figure 1.Map of samples taken in the region of Oulmes

Figure 2 .
Figure 2. Partitioning of the variables in the PCA F1 and F2 axes.

Table 1 .
Data for irradiation, cooling, position and elements determined.

Table 3 .
Results obtained for granite samples of Oulmes region.

Table 4 .
Major elements correlation.demonstratesa notably distinct pattern, as its correlation with other oxides displays a somewhat diminished value, standing at 0.47.This discrepancy in correlation strength for K 2 O could potentially signify intriguing variations in its chemical behavior compared to the other elements in this context.

Table 5 .
Correlation between all elements .

Table 6 .
Correlation between all elements .

Table 7 .
Correlation between all elements.