The regional structures of the region as a result to the tectonic evolution of the Arabian plate which includes the African and Arabian rift system, and collision of the Arabian and Eurasian plates, produce to the Arabian dome [1] - [4] . These structure evolutions led to different fracture and rifting system, i.e. East-African rift, opening of the Red Sea, and Dead Sea rift system. The tectonics evolutions were controlling to the intraplate volcanic activities in the Arabian Peninsula, which are sporadically found over an area that covers a distance of 7,000 Km from Yemen in the south through Saudi Arabia, Jordan, Syria, and up to Turkey in the north [5] - [7] . This intra- plate volcanism occurred after the break of Africa and Arabia, opening the Red Sea and resulting in Oligocene flood volcanism in Yemen and Ethiopia [6] [8] . Furthermore, an extensive late Cenozoic intraplate volcanism covers the central Jordan, which may reflect the lithosphere extension [9] .

This study focused on the intraplate volcanic field in central Jordan Ar-Rabba Basalt (RB). The volcanism in Jordan occurs as sporadic volcanic centers along the eastern side of the Jordan Rift (Figure 1). These volcanoes are clearly associated with continental rifting and inception of the Dead Sea plate boundary. The relationship between magmatism and tectonic of the intraplate volcanism has been reported by [10] , indicating that alkaline volcanism in Jordan is similar to the Arabian intraplate volcanic fields, which erupt through two main fissure systems along the eastern margin of the Dead Sea rift in the east-west direction [11] [12] . The volcanism might have probably commenced during the Miocene period and continued to Pleistocene [13] . The K-Ar age of Jordan basaltic activity is divided into three episodes: Oligocene to early Miocene (26.23 - 22.17 Ma), Middle to late Miocene (13.97 - 8.94 Ma), and late Miocene to Pleistocene (6.95 - 0.15 Ma) [14] - [16] . The Jordan basalt is distributed in three main regions based on their mode of occurrences, within Jordan rift (e.g. Zara basalt), central Jordan (e.g. El-Lajjun, Ar-Rabba (Shihan) basalt and NE-Jordanian Harrat (with an area 11,400 km²) which is a part of the largest Harrat Al-Shaam and NW Jordan Ash-Shuna Ash-Shamaliyya Area [17] - [19] .

The basalts in central Jordan have been found to occur in seven places, namely, Tafila, Wadi Dana, Jabel Shihan (RB), El-Lajjoun, Jurf Al-Darawish, Ghor Al-Katar, and Wadi Zarqa-Ma’in, in the form of plateau basalts, local flows (wadi fills), or individual volcanic bodies (cones, plugs, and dikes) [19] . Some doloritic dykes observed to occur along the major faults, such as Karak-Al-Fayha fault zone, Wadi Dana, Tafila, and Ar-Rabba plateau [13] . The objective of this study is to investigate the petrography, geochemistry, and petrogenesis evolution of the intercontinental basaltic flow at Ar-Rabba area, which is in the east of Dead Sea in central Jordan; to determine the origin and type of the parental magma; and to investigate the tectonic setting evolution of the RB region.

The RB is located about 13 km Northeast of Al-Karak city at 31˚15'3468 to 31˚15'3488N and 35˚30'752 to 35˚30'760E (Figure 1). The RB flow covers an area of about 20 km² with arc like strip width about 0.2 to 0.5 km with an average thickness 1 - 5 m [13] . The exposure strata along the sides of Wadi Abu-Jubayba, Wadi ad Dahalya, Wadi imra, Wadi ad Dafall, Wadi al Hidan and Wadi adh Dhira area. This basalt belongs to the middle Pleistocene and consistence with the second stage of the opening of the Red Sea over the last 5 Ma [17] [20] . The RB seen in the field cover by Al-Hisa Phosphorite unite (Belqa Group) of Campanian age [21] [22] , and coverd by fluviatile, lacustrine gravels and soil.

The study area is affected by different structures, such as Siwaqa fault with east-west direction and extends from the Dead Sea to Wadi Sirhan, and Ed dhira fault are two major trending NE-SW. The N-S trending fractures are parallel to the Dead Sea transform fault, where as the E-W fractures lie parallel to Siwaqa fault Hasa fault and Zarqa-Ma’in fault [23] .

A total of 30 representative rock chip samples were collected from the outcropping AR-Rabba Basalt (RB). The samples crushed and powdered using a stainless steel Jaw Crusher and an Agate Ball Mill machine, to obtain grain size less than −80 μ. The samples were quartered in order to get a statistically representative (splitter) fraction and powdered using two geochemical techniques at the Natural Resources Authority (NRA) labs.

The major elements were analyzed on fused glass discs-like pellet (bead) by using a Phillips X-Ray Florescence Spectrometry (XRF) Majex PW-2424 Model at the Al al-Bayt University. A total of 2 gram of the powder samples were mixed with 8 gram of lithium tetra borate and fused in platinum crucibles over gas burners (1000˚C) for 1 h. The melts were poured into a mold to create glass disks. The Loss on Ignition (LOI) was determined by the weight lost after melting at 1000˚C.

The trace elements were analyzed by decomposition using Ione Inductively Conductive Coupled Plasma Emission Spectroscopy (ICP-AES) at Natural Resources Authority Labs. A total of 1 gram of the powdered <80 μ sample mixed with 3 gram of sodium peroxide (Na₂O₂) were placed in a zirconium crucible, and fused by heating it to 450˚C for 45 mints, to obtain a sinter. Subsequently, 72 ml of deionized water was added to it, and stirred for a few mints; then 28 ml of diluted HCl in a ratio 1:1 was added to obtain clear solutions that were used to determine the trace element concentrations. Thin sections were prepared at the University of Al al-Bayt and petrographically investigated via polarizing microscope type Lico proccer with different magnifications.

The geochemical data were processed and pictorially represented by using the computer program Igpet 32. CIPW-Norm calculations were carried out by using the Excel sheet [24] .

The major and trace elements of the RB were used to construct discriminatory diagrams, to help for the classification, nomenclature, and interpretation of the tectonic setting of the RB. Classification for [33] , the RB samples plotted in the alkaline to subalkaline rock field (Figure 8(a)). The AFM diagram shows the RB samples plotted in the calcalkaline series (Figure 8(b)). The ternary diagram for Ti-Zr-Y based on [44] was distinguished among island-arc tholeiitas, MORB, calc-alkaline, and intraplate basalt, all the RB samples were plotted within the plate basalt field (Figure 9(a)). On the other hand, Ti-Zr-Sr digram shows all the RB samples plotted in the calc- alkaline basalt field (Figure 9(b)) [44] . The MgO-FeO_(tot) ? Al₂O₃ diagram for [45] , shows the RB samples ploted within continental basalt field (Figure 10).

The low content of SiO₂ (41.79 to 54.55 wt%) and high content of MgO (5.4 to 11.7 wt%) and total FeO (10.40 - 15.20 wt%) indicated the natural fractionation of the RB. The high concentration of Cr (18 to 385 ppm) with average 246.87 ppm is consistent with findings reported for primary magma |(e.g., 241 ppm [30] , 257.6 ppm [11] , 313.6 ppm [19] , 125.3 ppm [46] , 95 ppm [42] . The high Mg# (average 55.66) for RB is similar to that reported for rock affected by fractionation or accumulation of clinopyroxene, orthopyroxene, and olivine and

plagioclase [34] . The Rayleigh fractionation equation for [47] , are used to modeled the mineral fractionation, where C_l is the concentration of a trace element in the residual melt; C_o is the concentration of a trace element in the original melt; F is the fraction of melt that remains, and D is the bulk partition coefficient. The partition coefficient of Sr and Ba modeled of the mineral fractionation vector diagram in Figure 11, which indicated that the RB rock samples had fractions of clinopyroxene, orthopyroxene, olivine, and traces of plagioclase.

The batch melting equation for [47] are used to study the degree of partial melting of the RB. The equation

, where F is the melting degree; C_o and C_l are the concentrations of the elements in the source (original) and liquid, respectively, and D_o is the bulk distribution coefficient of the elements in the initial assemblage and minerals entering into the liquid. The distribution coefficient model for Cr and Co, and the

concentration of the large ion lithophile elements (LILE) was found to exhibit primitive composition [27] . The degree of partial melting (F) calculated by using the concentrations of the oceanic crust sources. The studied RB samples shows an average partial melting degree of around 10%, which documented with the previously published results for Jordanian and Arabian interpolate basalt [11] [19] [31] [48] .

The geochemical information for major and trace elements are used to explain the natural source of RB, and it is used to explain the mantle sources of partial melting. This indicates by using trace element ratios, such as Zr/Nb and K/Ba ratios [49] . The high content of Zr/Y and TiO₂/Y ratios and low content of Y indicate that to the garnet - bearing source rocks [50] [51] . The spider diagram for normal mid-ocean ridge basalt (NMORB) for the studied volcanic rocks (Figure 12(a)) presented enrichment of the strongly incompatible LILE such as Ba and K, depletion of Nb relatively to K, enrichment of Pb over Ce, and light rare earth elements (LREE) enrichment La over heavy rare earth elements (HREE) and Y, which showed high similarity to MORB. The mafic volcanic RB exhibited negative Nb anomalies and positive Pb anomalies, but presented higher LILE enrichments. The negative anomalies of Ba, Sr, P, and Ti may be attributed to the fractionation of feldspar for Ba and Sr depletion, apatite for P depletion, and (Fe-Ti) oxides for Ti depletion [38] . The primitive mantle value of the rock (Figure 12(b)) showed a positive Nb peak, which conforms to the tertiary to recent continental alkali basalt provinces [52] - [54] and indicates that the RB is the product of lithosphere from upwelling asthenospheric mantle [19] [34] [36] [55] .

The RB introduced within Miocene to Pleistocene volcanism at central Jordan. It is produced within intraplate to continental calc-alkaline to alkali basalt. The samples study covered at Al-Rabaa basalt flow about 20 km². The following is the conclusion of the present study:

1) The mineral composition of RB is as follows: plagioclase, pyroxene, olivine, and opaque minerals (magnetite), with secondary minerals such as iddingzite, calcite, and clay. The main textures observed trachytic, glo- meroporphyritic, vesicular, amygdaloidal, ophtic and supohtic.

2) The chemical classification of RB uses major elements into basaltic-calc-alkaline to alkali basalt and includes into sodic series.

3) The tectonic setting for the discrimination diagram showed that the RB samples were ploted within inter- plate basalt, calc-alkaline basaltic and continental basaltic field.

4) The vector diagram for fractional crystallization model for RB showed the presence of clinopyroxene, orthoproxene, olivine, and traces of plagioclase. Documented with the published results for Jordanian and Arabian interpolate basalt, the distribution coefficient of Cr and Co indicated a partial batch melting of RB around to 10%.

5) The spider diagram for NMORB and MORB showed enrichment of the incompatible LILE such as Ba and K, and depletion of Nb relatively to K, enrichment of Pb over Ce, and Light Rare Earth Elements (LREE) enrichment La over heavy rare earth elements (HREE) and Y. Furthermore, RB exhibited negative Nb and positive Pb anomalies, which indicated that RB was a product of lithosphere from upwelling asthenospheric mantle.

The author is thankful to Natural Resources Authority (NRA) for assistance in the analysis by Ione Inductively Conductive Coupled Plasma Emission Spectroscopy (ICP-AES) analysis for trace elements (contribution for Regional Geochemical Prospecting Project for central Jordan). The author is also grateful to Al al-Bayt University (Water, Environment and Arid Regions Research Centre), for performing the XRF analysis for major elements, and to Mr. Adnan Mashaqbeh for help in the preparation of thin sections. The authors are also grateful to Engineer Aya Bany Yaseen for her help in the field and Photomicrographs preparation. The author is indebted and grateful to the anonymous reviewers for their comments that helped in improving the manuscript.

Ibrahim Ahmad Ali Bany Yaseen, (2016) Petrography, Geochemistry and Petrogensis of Basal Flow from Ar-Rabba Area, Central Jordan. International Journal of Geosciences,07,378-396. doi: 10.4236/ijg.2016.73030