Basaltic Sheet Research Articles

Pictorial 2 : Filament Shaped Fungi-like Structures Surrounded by Calcite in Basalt Sheet Flow Obtained by ODP Leg 200 Site 1224F

Pictorial 2 : Filament Shaped Fungi-like Structures Surrounded by Calcite in Basalt Sheet Flow Obtained by ODP Leg 200 Site 1224F

Cenozoic paleogeography of the central Mogollon Rim–southern Colorado Plateau region, Arizona, revealed by Tertiary gravel deposits, Oligocene to Pleistocene lava flows, and incised streams

Eocene to Pleistocene paleogeography of the Mogollon Rim–southern Colorado Plateau region in central Arizona is interpreted by use of Tertiary sedimentary deposits and mafic lavas that have been correlated on the bases of provenance of pebbles, stratigraphic sequence, geomorphic positions of deposits and flows, published K-Ar ages, tracing of lava flows to vents, and lava textures and structures. Five categories of Tertiary sedimentary deposits are (1) Paleocene(?) to Oligocene(?) fluvial and lacustrine deposits on the margin of the Colorado Plateau that were derived from local and distant southern sources; (2) Oligocene(?) to Miocene deposits in valleys at the base of the Mogollon Rim that were derived from local and distant southern sources; (3) Oligocene(?) to Pliocene locally derived gravel on pediments and in canyons along the rim; (4) Miocene locally derived lag gravel beneath sheet flows on the plateau; and (5) Miocene to Pleistocene locally derived channel-filling gravel on the plateau. Mafic lavas used are (1) upper Oligocene to lower Miocene basalt and minette in the Transition Zone; (2) Miocene pahoehoe sheet flows on the Colorado Plateau and draped over the Mogollon Rim; (3) middle Miocene to Pleistocene cones and flows of basalt scattered across the region; and (4) Pliocene to Pleistocene basalts of the Mormon and San Francisco volcanic fields. Basalt sheet flows in ten middle (ca. 12 Ma) and upper (ca. 6 Ma) Miocene flow fields, traced to 12 low-profile vent structures, cover nearly 30% of a 9000 km2 area of the central Mogollon Rim region and depict the paleogeography at the times of eruption. Principal conclusions are: (1) the Mogollon Rim developed near its present position after Precambrian rocks in central Arizona had been unroofed during the Paleocene to Eocene Epochs, and before late Oligocene to early Miocene mafic volcanism; (2) after erosional quiescence during the Paleogene, Triassic strata were stripped off the southern Colorado Plateau in a Miocene to Pleistocene erosional sweep from the southwest to the northeast; (3) incision of meanders on the Mogollon Slope occurred in the late Pliocene to Pleistocene Epochs as a result of integration of the Little Colorado River with the Colorado River in the Grand Canyon.

Cyclic volcanic stratigraphy in a late ordovician marginal basin, West Norwegian Caledonides

The well-preserved extrusive sequence of the Solund-Stavfjord Ophiolite Complex (SSOC) in the West Norwegian Caledonides enables reconstruction of the uppermost oceanic crust that developed in a marginal basin. Basaltic sheet flows, pillow lavas and volcanic breccias are the main components of the extrusive sequence and show stratigraphic and structural evidence for a cyclic development. The first stage in a volcanic cycle is characterized by high extrusion rates yielding sheet flows, commonly with the thickest flow units at the base. Sequences of sheet flows can be correlated laterally for at least 6.5 km. Pillow lavas succeed the sheet flows later in a volcanic cycle with progressively smaller pillows forming at decreasing extrusion rates. Volcanic breccias occur towards the end of a volcanic cycle, but may also occur at lower stratigraphie levels. They are made generally of pillow breccias and hyaloclastites. The extrusive sequence of the SSOC oceanic crust was constructed through seven volcanic cycles that resulted in stratigraphic units with thicknesses ranging from 40 to 225 m. This architecture is comparable to sequences in in situ oceanic crust developed along slow- to intermediate-spreading ridges.

The Petrology of Mullite-bearing Peraluminous Xenoliths: Implications for Contamination Processes in Basaltic Magmas

A suite of high-level inclined sheets ranging in composition from basalt through to rhyolite is intruded into the Palaeogene lava field and underlying Moine Supergroup basement rocks around Loch Scridain, Isle of Mull, Scotland. Many of the sheets are highly xenolithic, containing a wide variety of crustal xenolith types derived from the Moine metasedimentary rocks, along with various gabbroic cumulate xenoliths. The most common xenolith types are almost pure quartzites and a variety of mullite-bearing aluminous buchites, many of the latter having thick crystalline selvages of plagioclase, corundum and aluminous spinel. The plagioclase is highly calcic (up to An87), and adjacent to the host basalt is commonly oscillatory zoned, implying crystallization from a melt. Trapped between plagioclase crystals are pockets of quenched, contaminated basic melt, which contain skeletal plagioclase and clinopyroxene, and preserve evidence of local mixing between the host basalt and the aluminous crustal melts. Sr and Nd isotope values of the buchite cores [e.g. (87Sr/86Sr)55 = 0.7074–0.7115], plagioclase selvages [e.g. (87Sr/86Sr)55 = 0.7137–0.7148], and associated trapped melts [e.g. (87Sr/86Sr)55 = 0.7126–0.7128], imply a complex series of magma–xenolith interactions. The textural characteristics, mineral chemistry and isotope geochemistry of these rims suggest that they have crystallized from a hybrid liquid formed by the complex interaction of the aluminous liquids with basic magmas. Such interaction proceeded via liquid–liquid diffusion, physical mixing of melts and a variety of reactions between the crystallization products of the buchites and the basaltic liquids. These crustal xenoliths preserve a detailed record of mineral–melt reactions within a suite of basaltic sheets, dominated by both the production of granitic melts and the ‘bulk’ melting of Al-rich micaceous lithologies.

Reevaluation of vesicle distributions in basaltic lava flows

A fundamental dichotomy in the study of basaltic lava flows is that observations of active flows are restricted to flow surfaces, yet older flows are often exposed only in vertical cross section. Cross-sectional exposures of an inflated basaltic sheet flow emplaced in Kalapana, Hawaii, from 1990 to 1991 provide an unusual opportunity to merge these two viewpoints, permitting the development of the internal structure of the flow to be viewed in the context of its known emplacement history. We demonstrate that fundamental features of the flow structure—a thick upper vesicular crust that diminishes downward in overall vesicularity, a dense flow interior, and a thin lower vesicular zone—are generated through syn-emplacement cooling of upper and lower flow crusts. Both the inverse correlation of overall vesicularity and vesicle size and the constant relative thickness of the upper vesicular zone are unique to inflated flows and permit a reinterpretation of flows previously interpreted to be ponded (rapidly emplaced). Identification of inflation, in turn, implies near-horizontal paleoslopes and permits estimates of flow duration based on upper flow crust thickness.

Stratigraphic and structural evolution of the Tertiary Cosmelli Basin and its relationship to the Chile triple junction

At the Taitao Peninsula, in southern Chile (46.5 ° S), an active mid-ocean ridge is being subducted under the South American continent. Continental crust south of the current triple junction has experienced subduction of three ridge segments since the mid-Miocene. A series of Mid-Late Tertiary sedimentary basins lies inboard of the triple junction: the Cosmelli basin lies in the region which has experienced the earlier ridge subduction events. Within the Cosmelli basin fill, abrupt facies dislocations give clear evidence of marked base level changes. Four sequence boundaries are delineated, with an upward increase in degree of facies dislocation, which is believed to reflect increasing magnitudes of base level fall. The lower part of the basin fill is folded and then thrust eastward as a series of imbricate slices, while the overlying, greater thickness of fluvial sediments is only gently tilted westwards. This geometry indicates that the early basin fill was deforming due to contractional tectonics while the later basin fill was being deposited; these processes controlled accommodation space and thus stratigraphic architecture during much of the basin life. This complex basin history, plus the presence of basaltic sheet intrusions may reflect the underlying slab history as successive ridge segments were subducted.

美濃‐丹波帯に貫入する高マグネシア安山岩および玄武岩シートのＫ‐Ａｒ年代

美濃‐丹波帯に貫入する高マグネシア安山岩および玄武岩シートのＫ‐Ａｒ年代

Geodynamic of the Gulf of Suez-Red Sea rifting and origin of within plate magmatism

This study is an attempt to follow up the overall picture of the geologic processes of the “Wilson Cycle” in the Gulf of Suez Red Sea region. A plate-tectonic model is suggested covering the Pan-African collisional tectonics, post-Pan-African magmatism in space and time, and rifting stages in the Red Sea region. Field relations, petrography, and petrochemistry of the Tertiary basalt sheets of Abu Zenima area, Sinai, have been studied and correlated with some petrochemical data of Phanerozoic magmatic activities in the Red Sea region. The sequence of events of the tectonics and magmatic activities in the Gulf of Suez-Red Sea rift system may belong to six stages post Pan-African orogeny: (1) Paleozoic-Cretaceous continental bimodal alkaline magmatism resulting from the sinking of detached subducted oceanic plates, in the late stages of the Pan-African collisional tectonics. Consequently causing convection currents around them and partial melting of a deep undepleted mantle source; (2) Paleogene crustal doming and stretching as a result of asthenosphere upwelling activated by a long period of (≅ 300 m.y.) within plate alkaline magmatism; (3) Late Oligocene fissure-eruption of transitional (T-type MORBs) plateau basalts, dykes and sills on a regional scale. The transitional character of this basaltic activity is attributed to the soaking of the asthenosphere, during its slow upwelling, in the rising alkaline magmatism; (4) Early Miocene narrow long continental rifting in the Gulf of Suez-Red Sea region, probably due to a thermal contraction process resulting from the eruption of the Tertiary transitional, fissure-eruption basalts in large volumes from the upwelled asthenosphere; (5) Initiation of crustal separation of the very early stage of seafloor spreading, which is most probably characterized by mafic igneous rocks underplating of the crustal faulted blocks by dyke injection and related plutonic rocks; (6) Pliocene oceanic rifting and seafloor spreading generating N-type MORBs in the central parts of the Red Sea axial trough. In this stage, subsidence of the Red Sea passive marging could be due to a second stage of thermal contraction resulting from the extrusion and crystallization of asthenosphere material to construct the new oceanic crust.

Sea-floor sulfides at the Hoydal volcanogenic deposit, central Norwegian Caledonides

The Hoydal volcanogenic massive sulfide deposit is associated with thick basaltic sheet flows toward the middle of a 1- to 2-km-thick, low-metamorphic, inverted, Lower Ordovician ophiolitic volcanite sequence in the central Norwegian Caledonides, just east of the major (25+ million metric tons) orebody at Lokken.Hoydal is one of the very few Scandinavian Caledonian strata-bound volcanogenic massive sulfide deposits which retains dominantly sea-floor depositional features, due to the minimal effects of later deformation and metamorphism. This study documents these features and compares them with those of recently formed and presently forming sea-floor sulfides.The layered massive sulfides at Hoydal are closely related to a sheetlike feeder zone as well as to extensive jasperoid layers and fault-scarp talus deposits. A palinspastic reconstruction relates the ores to sea-floor deposition along elongated, fissure-controlled, hydrothermal conduits; the talus breccias, involving sulfides, jaspers, and the volcanites, are considered to be due to movements along the feeder-fissure-fault system.Chemically the ore is dominated by Fe, Zn, and Cu, the two latter elements being highly variable and showing no significant correlation with each other. Ag is correlated with Cu, suggesting that most Ag is contained in chalcopyrite. Au shows a strong association with both As and Sb, and tennantite is suggested as a possible Au bearer.Investigations of ore textures have led to definition of several stages of mainly sulfide deposition. An early period of fine-grained colloform pyrite (+ chalcopyrite, sphalerite, and galena) deposition succeeded an earlier phase in which tabular pyrrhotite was probably formed. The colloform pyrite phase was succeeded conformably by coarser grained, clean, crystalline, sub- to euhedral pyrite, deposited in cockadelike structures outside the colloform structures. Contemporaneously, recrystallization of parts of the colloform pyrite produced (internally) euhedral, often poikilitic, pyrite.Both these noncolloform pyrites are attributed to a period of higher temperature conditions resulting from the sealing-off of cold seawater from the rising hydrothermal fluids. These conditions led further to the deposition of chalcopyrite as both open-space fillings and replacement of early-formed sulfides, accompanied by chalcopyrite disease in earlier sphalerite. The last main stage of sulfide deposition introduced the major part of the sphalerite apparently by open-space filling.Comparisons with present-day sea-floor sulfides, as described in the literature, reveal certain special features of the Hoydal sulfides. In common with the major orebody at Lokken, they appear to have been deposited in connection with a phase of vigorous volcanic activity, consequent upon the intrusion of new, hot, mafic magma to a high level in the oceanic crust which gave rise to large-scale hydrothermal convective systems.The main period of high-temperature chalcopyrite deposition was followed by a phase when hot solutions, deficient in Cu and Fe, caused redissolution of parts of the sulfides deposited earlier and the formation of a highly porous, residual pyrite + or - chalcopyrite ore. This was filled in and cemented by late, low Fe sphalerite and quartz introduced by low-temperature solutions during the waning stages of hydrothermal activity.Marked enrichment of elements such as Zn, Pb, Ag, Au, and Sb, relative to Cu and Fe, seems to be due to the purging of the last-mentioned elements from the solutions by large-scale deposition of chalcopyrite and pyrite within the underlying oceanic crust.

Geophysical Mapping of a Buried Basalt/Sedimentary Interface, Eastern Sudan

ABSTRACTThe El‐Shawak area in eastern Sudan lies within a large synclinal basin known as the Gedaref Basin, composed principally of elastic sediments of the Nubian Sandstone Formation which are overlain by sheets of basalt and dolerite and underlain by a metamorphic Basement Complex.As a part of a hydrogeological research project in the area, gravity and seismic refraction techniques were combined to locate the extent of the basaltic flow and to determine the thicknesses of the sedimentary formations.The results of these studies show that the topography of the Basement Complex is undulating and characterized by two troughs separated by subsurface ridges. The thicknesses of the Nubian Formation sediments range from 50 m (164 ft) to greater than 250 m (820 ft). Although the thicknesses of the Nubian Formation are favorable for ground‐water occurrence, the yield is very limited because the sediment succession is composed largely of compact mudstone.The application of the gravity method in the El‐Shawak area has shown that a polynomial trend‐surface fit can be used to separate the regional and the residual components to reflect local geological features.

Field evidence for turbulence during flow of basalt magma through conduits from southwest Mull

AbstractThe swarm of Palaeocene inclined sheets around Loch Scridain in southwest Mull includes basaltic sheets which contain abundant metasedimentary xenoliths that show evidence for having been partially molten. In contrast with the majority of dyke-like conduits worldwide, which have essentially planar margins, the contact of one of these xenolithic sheets with Moine metasediments is irregular along a segment where it crosses interbedded psammites and pelites. Relatively fusible mica schists have been excavated by the magma, on either side of a massive refractory quartzite horizon. Furthermore, the dolerite of the sheet shows only a slight reduction of grain size, through a zone 0.5 m wide, adjacent to its margin, in contrast with the pronounced marginal chilling which characterizes most intrusions of the Loch Scridain swarm. These field relationships are interpreted as evidence that the basic magma which formed this sheet flowed with local turbulence during its emplacement. The estimated liquidus of the magma (1130 °C at 1 atm) is approximately 200 °C above the solidus of pelitic horizons in the country rock, but far below the solidus of the quartzites.

Application of effective thermal insulating materials in firing furnaces

It was established that the application of thermal insulation in high-heat thermal units makes it possible to save up to 2 tons of standard fuel per year. A survey of the furnace installations of the porcelain and faience field and the thermal balance calculations showed that the walls and the roof of the firing zone of the furnances form the main sources of heat losses. Basalt sheets were introduced for thermal insulation of the roof. The use of BTK-1 basalt sheet as a supplementary thermal insulation makes it possible to reduce heat loss through the furnace roof by 13% as compared to the conventional method of thermal insulation of the tunnel furnace using diatomite chips.

Subsurface Geology of Tertiary Rocks of Northeastern District of Western Desert, Egypt: ABSTRACT

The lithofacies analysis of the Tertiary rocks reveals two ancient subbasins at the north and southeast of the northeastern district, Western Desert. The southeastern subbasin seems deeper than the northern one as it received relatively thicker Paleocene and early and middle Eocene rocks. The lithofacies of the Paleocene and early and middle Eocene sections are mainly calcareous. The clastic ratio ranges from 0.05 to 1. Shale predominates in the late Eocene rocks. The clastic ratio is more than one everywhere. The Paleocene rocks seem to have accumulated in a lagoonal environment of epineritic depths. Semi-restriction of water circulation at the southeastern subbasin was caused by an elongated ridge, separating the two subbasins. The Paleocene rocks of the northern subbas n indicate accumulation on an unstable shelf, i.e., slow deposition in a rapidly subsiding basin or at least slow deposition in an overall carbonate aerobic environment. Widening of the northern subbasin occurred during the early Eocene. The Paleocene environmental conditions seem to have prevailed during the early and middle Eocene. During the late Eocene, rocks of shallow-water and current-agitated environments accumulated. The lower clastic layers of the Oligocene, having a sand/shale ratio less than one, indicate a clastic shoreline environment-lagoonal subenvironment. The sediments of such an environment are brought down by rivers and reworked by waves and currents. The Oligocene clastics are overlain by a basaltic sheet at the eastern part of the district. The depocenter of the nor hern middle Miocene subbasin lies farther north. The sand/shale ratio increases to the south, being more than one. The middle Miocene lithofacies indicate rock accumulation in a contemporaneously subsiding basin under lagoonal or delta-front conditions at the southern part of the district. Marine stagnant-bottom-water conditions prevailed during the accumulation of the middle Miocene rocks at the northern parts. The Pliocene shoreline shifted farther northward. The Pliocene rocks seem to have accumulated in lagoons, where the inflow exceeded evaporation and alternating periods of exposure and flooding by either fresh or saline water of poor circulation prevailed. The tectonic instability of the district was initiated by volcancity during the late Oligocene. This volcanic activity was acc mpanied by uplifting, folding, and faulting of Oligocene and older rocks. The uplifting of the southern part was accompanied with subsidence of the northern one. The subsidence was associated with vertical block movements of the basement rocks. Basaltic magma climbed along faults. The folds are of the brachyanticlinal type, affected by faulting forming a median horst block. This block remained high for a great period of time. The axes of folding are parallel to the fault trends due to their association with the vertical block movements of the basement. The northern flanks of the folds are relatively steeply dipping. The middle Miocene and Pliocene rocks are not affected by faulting. The source lands of those sediments are deduced as nearby low elevated lands affected by the same tectonic events that affected the depositional basin itself during different epochs. End_of_Article - Last_Page 456------------

Intense hydrothermal activity at the axis of the east pacific rise near 13�N: Sumbersible witnesses the growth of sulfide chimney

A submersible study of a fast spreading (12 cm yr-1) Mid-Ocean ridge segment (East Pacific Rise near 12°50′ N) led to the discovery of intense hydrothermal activity. Twenty four sites with active vents and sixty inactive hydrothermal deposits were found within a narrow graben averaging about 300 m in width along a 20 km long segment of the ridge crest. The graben is floored with fresh basaltic sheet flows including collapsed pits or lava lake structures. From both deep towed camera stations and manned submersible observations, it is estimated that the average spacing between the ridge axis hydrothermal deposits averaging in size 10–50 m in diameter lies between 100 to 200 m.

Hydrogeology of the Syrian steppe and adjoining arid areas

Summary Several major sedimentary basins, in which thick sequences of Palaeogene marls and Neogene-Quaternary sediments have accumulated, can be distinguished in the arid zones which extend from the Great Nefud in Saudi Arabia to the Euphrates river in Syria. Structurally, they represent areas of relative subsidence formed between the Rutbah-Ha'il arch, the Jordan uplift and the Halab uplift. The Syrian steppe and adjoining areas can be subdivided into eastern, western and north-western regional ground-water flow features which follow north-westerly (Palmyrian) and south-south-westerly trends. The eastern regional flow system in the permeable Palaeozoic and Mesozoic strata is related to the development of the broad domal structure of the Rutbah-Ha'il arch. Transmission of flow parallel to a system of north-north-westerly lineaments occurs from the Rutbah area of Iraq to the Wadi-el-Miah area of Syria. Step faulting and the minor anticlinal structures developed in this latter area seem to influence upward leakage from the deeper aquifers into the Cretaceous and Palaeogene chert aquifers. Groundwater transmitted westwards from the Rutbah-Ha'il arch is retarded by the marly facies of the Upper Cretaceous and Palaeogene in the Wadi Sirhan basin. Minor chert aquifers, however, transmit a portion of the flow. Discharge occurs in a zone along the eastern margin of the Wadi Sirhan. The western regional flow system differs from that in the east in that hydraulic interconnection between the upper aquifers with the underlying Mesozoic is negligible. The recharge zone for this system coincides with the higher portion of Jebel-el-Arab. Groundwater transmission in the complex sequence of basaltic sheets of the Syria-Jordan plateau region is controlled by two fracture systems, in addition to the usual lava flow conduits. The north-western regional system is recharged in the Anti-Lebanon and flows south-westwards in fractured limestones and dolomites. Discharge occurs mainly via karstic springs. Upward leakage may occur into the Ghouta gravel aquifer and eventually may be lost by evaporation from Ateibe lake. In the S Palmyrian moutains zone, a flow pattern controlled by linear en-echelon structures transmits groundwater in a north-easterly direction. Discharge from the system takes place at Sabkhet-el-Mouh, south of Palmyra. Hydrogen sulphide water, issuing along the south Palmyrian regional fault system, suggests relatively deep groundwater circulation. Isotopic studies indicate that groundwater age increases along the Palmyrian flow system.

ISOTOPIC AGE DETERMINATIONS ON A BASALT INTRUSION AND ULTRABASIC XENOLITHS, SOUTH BUTE, SCOTLAND

SUMMARY K-Ar isotopic age determinations are reported from a basaltic sheet and some xenoliths from South Bute, Scotland. The age of the intrusion, 309 ± 5 Ma (pre-middle Carboniferous), is in agreement with the date inferred from its petrology. The results from the ultrabasic xenoliths do not permit a simple interpretation.

The large fissure eruption in the region of Plosky Tolbachik volcano in Kamchatka, 1975–1976

The paper describes the course of the Large Tolbachik fissure eruption taking place in Kamchatka from July 6, 1975 to December 10, 1976. The eruption zone extended for 30 km. The formation of monogenic scoria cones nearly 300 m high, lava tubes and basalt sheets up to 80 m thick and more than 40 km2 in area and subsidence of the Plosky Tolbachik summit caldera to a depth of more than 400 m were observed during the eruption. The volume of eruption products amounted to more than 2 km3. It was the largest basalt eruption which has taken place in the Kurile-Kamchatka volcanic belt in historic time.

Thermal effects of basalt on continental crust and crustal contamination of magmas

A simple conduction-based heat-flow model is used to calculate the thickness of zones of continental crustal rock adjacent to basalt sheets which are raised to the temperatures of (1) hydrous mineral breakdown and (2) partial melting. Basalt emplacement leads to wide zones of partial fusion and aqueous fluid circulation at most crustal levels. Contamination of the basalt magma by partial melts or aqueous fluids is most effective where mag-matism is episodic and repetitive on a 0.1–1,000 yr time scale.

Origin and petrology of young oceanic central volcanoes: Are most tholeiitic rather than alkalic?

Nine small seamounts located on young crust (< 10 m.y.) near the East Pacific Rise were surveyed in detail and sampled by multiple dredges. Preliminary results indicate that most seamounts (closed elevations on the sea floor with about 1 km of relief) are volcanoes, but that some, especially those near fracture zones, may be fault blocks. The flanks and summits of the volcanoes are mostly composed of basalt sheet flows, hyaloclastite, and hyaloclastite breccia, whereas fault blocks contain mostly pillow lava. The rocks from the volcanoes show great chemical diversity. Most are large-ion-lithophile–depleted tholeiitic basalt similar to normal mid-ocean ridge tholeiite, with a wide range of 100 Mg/ (Mg + Fe+2) and other chemical abundances indicative of low-pressure fractionation. As a group, the samples also show large differences in (La/Sm)N, even in rocks from a single volcano. This provides evidence that some chemical heterogeneities in the source region of these basalts are small.

Rare-earth and trace elements of basaltic rocks of Ikuno Group, Japan.

Seven rare-earth elements (La, Ce, Sm, Eu, Tb, Yb and Lu), Ba, Co, Cr, Hf, Sc and Th have been determined by nondestractive neutron activation analysis and U by fissiontrack method on the basaltic rocks of meso-volcanic complex in Ikuno group, Hyogo Prefecture, Japan. The trace element abundances are discussed in terms of the petrological problems, especially, the origin of magma. The volcanic complex of Ikuno group consists of rhyolite, andesite, alteration of black shale and tuff, and dellenite. The basaltic rocks are found in the Ikuno group as sheet and dykes which intruded into Ikuno group. The basaltic sheet is alkalic rock and these dykes are high alumina basalt series.