Area studied in this paper is located in the northwest of city of Alasht. The most important varieties of studied rocks are volcanic and semi-volcanic rocks of basic nature. These rocks, which form a distinguishable s...Area studied in this paper is located in the northwest of city of Alasht. The most important varieties of studied rocks are volcanic and semi-volcanic rocks of basic nature. These rocks, which form a distinguishable solid mass on 1:100,000 geological map, belong to Cretaceous period. According to results of petrographic study, rocks of this area include olivine basalt, dolerite, gabbro and microgabbro, and all have almost similar chemical compositions. According to chemistry-based naming process carried out through TAS method, these rocks are entirely basalt and basic and are all products of Sub-alkaline-Tholeiitic magma. According to Harker diagrams, a magmatic differentiation can be observed in all volcanic rocks;furthermore, basaltic magma erupted in this area has undergone an alteration and possibly a crustal contamination. The spider diagrams plotted in this paper show that basic rocks of Alasht area (basalts, andesite basalts, dolerites, gabbros and microgabbros) are all mostly similar to ocean island basalts (OIB). Once field study, sampling and microscopic study stages were complete, ten samples were selected for chemical analysis and were analyzed by XRF method.展开更多
Tonnge basalt is a relatively small basaltic field situated in the Tigyaing Township, Sagaing Region, Myanmar. This basaltic field is considered as one of the occurrences of younger extrusive rocks along the major str...Tonnge basalt is a relatively small basaltic field situated in the Tigyaing Township, Sagaing Region, Myanmar. This basaltic field is considered as one of the occurrences of younger extrusive rocks along the major strike-slip fault of central Myanmar. The basaltic lava flows erupted and rested upon the Upper Miocene-Pliocene Irrawaddy Sandstone. Petrological and geochemical studies of the Tonnge basalts have not been carried out yet. This paper reports the results of petrological and geochemical investigation on the basalts from Tonnge area. These data have provided insight into the origin and petrogenetic processes during evolution. The petrographic characteristics of the basalts have been studied using polarizing microscope. The major- and trace-element compositions of basalt samples were analyzed using X-Ray Fluorescence. The Tonnge basalts are porphyritic, holocrystalline and consist of phenocrysts of olivine, plagioclase ± clinopyroxene which are set in the fine-grained intergranular groundmass of olivine, pyroxene, and opaque minerals. The basalts show typical characters of alkali olivine basalts. Trace element assemblage of the studied basalts plots on various discrimination diagrams as within-plate basalt erupted in the continental setting. A relatively small volume, monogenetic nature and unique geochemical characteristics of the basaltic lavas suggest that they are derived from a single, short-lived, discrete parental magma as a result of partial melting.展开更多
Five Late-Cenozoic olivine basalt samples, taken from 3 young volcanoes (Keluo, Lianhuashan and Qinglongshan) located in the north of Heilongjian Province, were dated by the conventional K-Ar dating method. The appare...Five Late-Cenozoic olivine basalt samples, taken from 3 young volcanoes (Keluo, Lianhuashan and Qinglongshan) located in the north of Heilongjian Province, were dated by the conventional K-Ar dating method. The apparent ages of whole rock are (0.06±0.01) Ma,( 0.15±0.03) Ma, (0.17±0.02) Ma, (21.10±0.13) Ma and (24.46±0.10) Ma, respectively. In the crushed sample grains (mush number 80-100)olivine(including phynocryst and xenocryst)was picked out under a binocular microscope, then apparent ages obtained are (0.03±0.01) Ma, (0.06±0.01) Ma, (0.07±0.03) Ma, (2.31±0.02) Ma and (1.50±0.21) Ma, respectively. The apparent ages of the olivine-picked out sample are come down (younger)50 to over 90. There are a lot of the Late-Cenozoic volcanic olivine basalt outcropping in eastern China, probably the age-datings of those basalt samples in which olivine grains are unpicked out are older than the true geological ages. The inference and conclusion drawn from those datings should be renewed.展开更多
The importance of this study is to identify the newly reordered and recognized basaltic intrusion for the first time in Maasser El Chouf in Lebanon. The recorded basaltic intrusion cut the Jurassic-Lower Cretaceous ro...The importance of this study is to identify the newly reordered and recognized basaltic intrusion for the first time in Maasser El Chouf in Lebanon. The recorded basaltic intrusion cut the Jurassic-Lower Cretaceous rock in this area. Necessary field inspection, geology, mineralogy and chemical tests were carried out on 8 basalt samples to determine their mineralogy, petrography and chemical composition. Representative samples have been tested with polarizing microscope, X-ray diffraction (XRD) and X-ray fluorescence (XRF). Petrographic and mineralogical studies show that the basalt is characterized by presence mainly of calcic-plagioclase feldspar, pyroxene-augite and olivine minerals. Secondary minerals of iron oxides also present (ilmenite and magnetite). The most appeared property is the alteration of olivine mineral to iddingsite that indicated highly weathered process. The composition of the basaltic samples reflects ultrabasic-basic type (Basanite-Tholeiitic basalt). The existence of volcanic activity occurred mostly with Pliocene age (< 2 Ma) as indicated by previous studies for similar basalt in Lebanon. Possibly, these boulders have been carried up from some deeper intrusive magmatic body under very active tension zones. Volcanism of Lebanon basalts belong to the alkaline olivine basalt, suite generally associated with tension, rifting and block faulting movements of the continental crust. Most of the volcanisms in Lebanon and in Harrat Ash Shaam Basalt from Syria and Palestine through Jordan to Saudi Arabia are related and connected to the opening of the Red Sea Rift System, making the area with tremendous volcanic tectonic activities.展开更多
The Zarqa-Ma’in basalt (MB) occurs near a plateau basalt (wadi fills) covering about 15 km2 of Makawir, Ataruz, and Hammat um Hasana cone areas in central Jordan. The tectonic evolution occurred through intraplate vo...The Zarqa-Ma’in basalt (MB) occurs near a plateau basalt (wadi fills) covering about 15 km2 of Makawir, Ataruz, and Hammat um Hasana cone areas in central Jordan. The tectonic evolution occurred through intraplate volcanism and erupted through fissure systems along the Dead Sea, transforming the fault during Miocene to Pleistocene period. Three stages of eruption of MB have been recorded during Pleistocene from 6 to 0.6 Ma. The petrographic analyses data show that the MB rocks are composed of plagioclase, olivine, pyroxene, and magnetite, including secondary minerals calcite, iddingsite, serpentine, and zeolite. Furthermore, the MB rocks have narrow ranges of major and trace element concentrations, and are of under saturated silica type and belong to sodic alkaline magma series. The geochemical characteristics of MB indicate that MB was derived from a slightly fractionated magma as reflected by its high MgO (6.3 - 11.7 ppm) concentration with Mg number from 0.41 to 0.61, low silica content (40.83 - 47.55 wt%), and high Cr and Ni concentrations (115 - 475 and 105 - 553 ppm, respectively). This basalt exhibited low degree of partial melting (10%) for garnet peridotite mantle source. The model mineral fractionation showed that the MB could be fractionated to clinopyroxene, orthopyroxene, olivine, and plagioclase.展开更多
文摘Area studied in this paper is located in the northwest of city of Alasht. The most important varieties of studied rocks are volcanic and semi-volcanic rocks of basic nature. These rocks, which form a distinguishable solid mass on 1:100,000 geological map, belong to Cretaceous period. According to results of petrographic study, rocks of this area include olivine basalt, dolerite, gabbro and microgabbro, and all have almost similar chemical compositions. According to chemistry-based naming process carried out through TAS method, these rocks are entirely basalt and basic and are all products of Sub-alkaline-Tholeiitic magma. According to Harker diagrams, a magmatic differentiation can be observed in all volcanic rocks;furthermore, basaltic magma erupted in this area has undergone an alteration and possibly a crustal contamination. The spider diagrams plotted in this paper show that basic rocks of Alasht area (basalts, andesite basalts, dolerites, gabbros and microgabbros) are all mostly similar to ocean island basalts (OIB). Once field study, sampling and microscopic study stages were complete, ten samples were selected for chemical analysis and were analyzed by XRF method.
文摘Tonnge basalt is a relatively small basaltic field situated in the Tigyaing Township, Sagaing Region, Myanmar. This basaltic field is considered as one of the occurrences of younger extrusive rocks along the major strike-slip fault of central Myanmar. The basaltic lava flows erupted and rested upon the Upper Miocene-Pliocene Irrawaddy Sandstone. Petrological and geochemical studies of the Tonnge basalts have not been carried out yet. This paper reports the results of petrological and geochemical investigation on the basalts from Tonnge area. These data have provided insight into the origin and petrogenetic processes during evolution. The petrographic characteristics of the basalts have been studied using polarizing microscope. The major- and trace-element compositions of basalt samples were analyzed using X-Ray Fluorescence. The Tonnge basalts are porphyritic, holocrystalline and consist of phenocrysts of olivine, plagioclase ± clinopyroxene which are set in the fine-grained intergranular groundmass of olivine, pyroxene, and opaque minerals. The basalts show typical characters of alkali olivine basalts. Trace element assemblage of the studied basalts plots on various discrimination diagrams as within-plate basalt erupted in the continental setting. A relatively small volume, monogenetic nature and unique geochemical characteristics of the basaltic lavas suggest that they are derived from a single, short-lived, discrete parental magma as a result of partial melting.
文摘Five Late-Cenozoic olivine basalt samples, taken from 3 young volcanoes (Keluo, Lianhuashan and Qinglongshan) located in the north of Heilongjian Province, were dated by the conventional K-Ar dating method. The apparent ages of whole rock are (0.06±0.01) Ma,( 0.15±0.03) Ma, (0.17±0.02) Ma, (21.10±0.13) Ma and (24.46±0.10) Ma, respectively. In the crushed sample grains (mush number 80-100)olivine(including phynocryst and xenocryst)was picked out under a binocular microscope, then apparent ages obtained are (0.03±0.01) Ma, (0.06±0.01) Ma, (0.07±0.03) Ma, (2.31±0.02) Ma and (1.50±0.21) Ma, respectively. The apparent ages of the olivine-picked out sample are come down (younger)50 to over 90. There are a lot of the Late-Cenozoic volcanic olivine basalt outcropping in eastern China, probably the age-datings of those basalt samples in which olivine grains are unpicked out are older than the true geological ages. The inference and conclusion drawn from those datings should be renewed.
文摘The importance of this study is to identify the newly reordered and recognized basaltic intrusion for the first time in Maasser El Chouf in Lebanon. The recorded basaltic intrusion cut the Jurassic-Lower Cretaceous rock in this area. Necessary field inspection, geology, mineralogy and chemical tests were carried out on 8 basalt samples to determine their mineralogy, petrography and chemical composition. Representative samples have been tested with polarizing microscope, X-ray diffraction (XRD) and X-ray fluorescence (XRF). Petrographic and mineralogical studies show that the basalt is characterized by presence mainly of calcic-plagioclase feldspar, pyroxene-augite and olivine minerals. Secondary minerals of iron oxides also present (ilmenite and magnetite). The most appeared property is the alteration of olivine mineral to iddingsite that indicated highly weathered process. The composition of the basaltic samples reflects ultrabasic-basic type (Basanite-Tholeiitic basalt). The existence of volcanic activity occurred mostly with Pliocene age (< 2 Ma) as indicated by previous studies for similar basalt in Lebanon. Possibly, these boulders have been carried up from some deeper intrusive magmatic body under very active tension zones. Volcanism of Lebanon basalts belong to the alkaline olivine basalt, suite generally associated with tension, rifting and block faulting movements of the continental crust. Most of the volcanisms in Lebanon and in Harrat Ash Shaam Basalt from Syria and Palestine through Jordan to Saudi Arabia are related and connected to the opening of the Red Sea Rift System, making the area with tremendous volcanic tectonic activities.
文摘The Zarqa-Ma’in basalt (MB) occurs near a plateau basalt (wadi fills) covering about 15 km2 of Makawir, Ataruz, and Hammat um Hasana cone areas in central Jordan. The tectonic evolution occurred through intraplate volcanism and erupted through fissure systems along the Dead Sea, transforming the fault during Miocene to Pleistocene period. Three stages of eruption of MB have been recorded during Pleistocene from 6 to 0.6 Ma. The petrographic analyses data show that the MB rocks are composed of plagioclase, olivine, pyroxene, and magnetite, including secondary minerals calcite, iddingsite, serpentine, and zeolite. Furthermore, the MB rocks have narrow ranges of major and trace element concentrations, and are of under saturated silica type and belong to sodic alkaline magma series. The geochemical characteristics of MB indicate that MB was derived from a slightly fractionated magma as reflected by its high MgO (6.3 - 11.7 ppm) concentration with Mg number from 0.41 to 0.61, low silica content (40.83 - 47.55 wt%), and high Cr and Ni concentrations (115 - 475 and 105 - 553 ppm, respectively). This basalt exhibited low degree of partial melting (10%) for garnet peridotite mantle source. The model mineral fractionation showed that the MB could be fractionated to clinopyroxene, orthopyroxene, olivine, and plagioclase.
