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Tectonomagmatic origin of some volcanic and sub-volcanic rocks from the Lower Benue rift, Nigeria

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Chinese Journal Of Geochemistry 2011年第4期30卷 507-522页

作者： Smart C. Obiora Nirmal S. Charan Department of geology University of Nigeria National Geophysical Research Institute Geological Studies Division

Petrological and geochemical studies on some volcanic and sub-volcanic rocks from the Lower Benue rift indicate that they are basalts, basaltic and doleritic sills, trachybasalt and trachyte which generally belong to the alkali basalt series. The alkaline affinity is clearly evident in both their normative and modal mineral compositions, as well as their chemical compositions. The generally high fractionation indices [(La/Yb)N] are 7.06 to 17.65 for the basaltic rocks and 23.59 to 135. 35 for the trachytic rocks, against low values commonly seen in subalkaline (tholeiitic) series, with strong enrichments in the incompatible elements. All this strongly supports their alkaline affinity. The basaltic rocks are generally fine-grained and porphyritic, consisting of phenocrysts of clinopyroxene and olivine in the groundmass of the same minerals together with plagioclase. The clinopyroxene is either diopside or clinoenstatite. The trachyte consists of oligoclase, orthoclase, biotite, quartz and exhibits typical trachytic, flow structure. The basaltic and doleritic sills are commonly altered, with calcite and epidote as common alteration prod-ucts. This alteration, which is reflected in the erratic behaviour of K2O, MnO and P2O5 on Harker variation diagrams, high values of LOI, strong depletions in the more mobile LILE (Rb, K, Ba and Sr) and high Th/Ta ratios, is attributed to the effects of an aqueous fluid phase and crustal contamination. On the whole, the mineralogical, as well as major-, trace-elements and REE data suggest that the rocks are co-genetic and most likely derived from differentiation of an alkali olivine-basalt magma, generating through variable low degrees of partial melting of probably an enriched lithospheric (upper) mantle following an asthenospheric uplift (mantle plume or intumescence) with HIMU signa-tures in a within-plate continental rift tectonic setting. This corroborates earlier results obtained for the intrusive rocks in the region.

关键词：次火山岩裂谷构造岩浆起源岩石学尼日利亚粗面玄武岩玄武质岩石单斜辉石

AEROMAGNETIC SURVEY AND GEOLOGICAL STRUCTURE OF OFFSHORE CHINA

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Science in China,Ser.B 1983年第9期26卷 996-1008页

作者：张用夏杨华 Aerogeophysical and Aerogeological Exploration division Ministry of geology and Mineral Resources Beijing

This paper discusses the characteristics of the regional geological structure of the Bohai Sea, the Huanghai Sea, the East China Sea and the South China Sea on the basis of the data achieved by aeromagnetic surveys over the past *** Huanghai Sea is an intercontinental sea which is tectenically similar, and can be connected, to the adjacent continental parts. It is a submerged part of the continent. Aeromagnetic survey shows that the deep structures in this area strike E-W, belonging to the Pal-Asiatic Tectonic Domain. The South China Sea is a typical marginal sea of the Western Pacific Ocean, resulting from the fracturing of the continental margin and the sea floor spreading from the Mid-Oligocene to the Miocene.

关键词： AEROMAGNETIC SURVEY AND GEOLOGICAL STRUCTURE OF OFFSHORE CHINA NEE

A novel approach to structural anisotropy classification for jointed rock masses using theoretical rock quality designation formulation adjusted to joint spacing

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第2期14卷 329-345页

作者： Harun Sonmez Murat Ercanoglu Gulseren Dagdelenler Applied geology division Geological Engineering DepartmentFaculty of EngineeringHacettepe UniversityBeytepeAnkara06800Turkey

Rock quality designation(RQD)has been considered as a one-dimensional jointing degree property since it should be determined by measuring the core lengths obtained from *** index of jointing degree(AI_(jd))was formulated by Zheng et al.(2018)by considering maximum and minimum values of RQD for a jointed rock medium in three-dimensional *** accordance with spacing terminology by ISRM(1981),defining the jointing degree for the rock masses composed of extremely closely spaced joints as well as for the rock masses including widely to extremely widely spaced joints is practically impossible because of the use of 10 cm as a threshold value in the conventional form of *** overcome this limitation,theoretical RQD(TRQD_(t))introduced by Priest and Hudson(1976)can be taken into consideration only when the statistical distribution of discontinuity spacing has a negative exponential *** index of the jointing degree was improved using TRQD_(t) which was adjusted to wider joint spacing by considering Priest(1993)’s recommendation on the use of variable threshold value(t)in TRQD_(t) *** applications of the improved anisotropy index of a jointing degree(AI'_(jd))to hypothetical jointed rock mass cases,the effect of persistency of joints on structural anisotropy of rock mass was introduced to the improved AI'_(jd) formulation by considering the ratings of persistency of joints as proposed by Bieniawski(1989)’s rock mass rating(RMR)*** real cases were assessed in the stratified marl and the columnar basalt using the weighted anisotropy index of jointing degree(W_AI'_(jd)).A structural anisotropy classification was developed using the RQD classification proposed by Deere(1963).The proposed methodology is capable of defining the structural anisotropy of a rock mass including joint pattern from extremely closely to extremely widely spaced joints.

关键词： Anisotropy index of jointing degree Anisotropy of rock mass Rock mass classification Jointing degree Theoretical rock quality designation

Systematic Revision of Trilobites from the Middle Ordovician(Darriwilian) Klimoli Formation of the Zhuozishan Area,Inner Mongolia,China

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Acta Geologica Sinica(English Edition) 2016年第6期90卷 1955-1975页

作者： LEE Seung-Bae LEE Dong-Chan WOO Jusun ZHANG Xingliang geology division Korea Institute of Geoscience and Mineral Resources Department of Earth Science Education Chungbuk National University division of Polar Earth-System Sciences Korea Polar Research Institute Early Life Institute and State Key Laboratory of Continental Dynamics Department of GeologyNorthwest University

New morphologic information permits systematic revision of trilobites from the Middle Ordovician Klimoli Formation of the Zhuozishan area, Ordos Basin, Inner Mongolia. The new assemblage is composed of 10 species of the Raphiophoridae, Nileidae, Asaphidae, and Telephinidae.？ An asaphid, aff. Mioptychopyge lashachungensis （previously Paraptychopyge lashachungensis） displays an intermediate morphology between the Chinese nobiliasaphine genera Mioptychopyge and Zhenganites. The pygidial doublure is regarded as the most significant character to differentiate Symphysurus klimoliensis （previously Nileus klimoliensis） of the Nileidae from such closely allied taxa as Poronileus. A nileid, cf. Peraspis kujandensis displays typical nileid morphology, unlike the type species, Peraspis lineolata, which might turn out to be an asaphid. Ampyx gongwusuensis sp. nov. of the Raphiophoridae is the first record of the genus in the Zhuozishan area and reveals morphologic details that might be employed to resolve Ampyx taxonomy in China. Morphologic differences between A. gongwusuensis and Abulbaspis ordosensis might represent a case of sexual dimorphism.

关键词： Invertebrate paleontology Trilobita systematics Klimoli Formation Darriwilian Zhuozishan Inner Mongolia

Mantle-derived Xenoliths and the Token of a Modern Back-Arc Geotherm Beneath Eastern China

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Science China Chemistry 1994年第4期37卷 472-480页

作者：金振民 H.W.GreenII R.S.Borch 金淑燕 T.N.Tingle T.E.Young Department of geology university of CaliforniaDavisCA95616USA Department of geology University of California Daves CA95616USA. division of Geomechanics China University of Geosciences Wuhan 430074 PRC

Xenoliths of garnet and spinel-garnet 1herzolite from Mingxi, Eastern China have been studied in terms of comprehensive methods of mineralogy, petrology, fabrics, mierostructures and infrared spectrum. The temperature and pressure equilibration of the xenolith have been calculated using the TEMPEST program with the two-pyroxene geothermometer of Bertrand and Mercier (1985) combined with the geobarometer of Nickel and Green (1985). The temperature and pressure of xenoliths range from^1300 K at 1. 9 GPa (60 km) to ~1500 K at 2. 6 GPa (80 km). The geotherm inferred from xenolith is excellently consistent with the measured surface heat flow (70 mW/m2) in Mingxi. A character of geothermal curve and conductive type suggest that these xenoliths are from the lithosphere, not from the asthenosphere. The geotherm and mierostructures and preferred orientations of minerals in the xenolith are consistent with tecon-ic thinning of the lithosphere in the present-day extensional back-arc environment.

关键词： mantle xenolith spinel-garnet Iherzolite geotherm thermal structure of the lithosphere extensional back-arc environment.

FORMATION OF LARGE-SCALE TECTONIC ELEMENTS FROM THE POSITION OF CENTRIFUGAL-INERTIAL FORCE ACTION

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Geotectonica et Metallogenia 2005年第1期29卷 13-33页

作者： Molchanov V. I. Paraev V. V. United Institute of geology Geophysics and Mineralogy Siberian Division of Russian Academy of Sciences Novosibirsk 630090 RussiaUnited Institute of Geology Geophysics and Mineralogy Siberian Division of Russian Academy of Sciences Novosibirsk 630090 Russia

We describe the earlier unknown, when applied to global tectonics, centrifugal inertial mechanism of lithosphere plate moving under the effect of forces appearing as a result of Earth’s planetary rotation. The mechanism stated gives an insight into global tectonics of plates with the indirect participation of emanation streams which, in their turn, are the derivatives of centrifugal and inertial forces of planetary motion. The application of this mechanism provides a logical explanation for the regularities of global tectogenesis including the formation of mountain ridges mainly of submeridional and sublatitudinal strike, and also the drift of continental plates from the east to the west and from the south to the north. The mechanism clarifies the significance of the Arctic and the Antarctic Circles as geodynamic barriers.

关键词： formation tectonic element centrifugal-inertial force section

Geochemical characteristics and genesis of volcanic and sub-volcanic rocks from porphyrite-type iron deposits in Ningwu metallogenic province,eastern China:Constraints from elements

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Journal of Central South University 2014年第7期21卷 2866-2876页

作者：刘震黄德志刘毓菡古黄玲汪龙 HARTWIG E.Frimmel 戴塔根 School of Geosciences and Info-Physics Central South University Geodynamics and Geomaterials Research division Institute of Geography and GeologyUniversity of Würzburg

Ningwu porphyrite-type iron deposits are located in Ningwu Mesozoic volcanic basin,which belongs to the middle and lower reaches of the Yangtze River metallogenic *** volcanic rocks can be divided into Longwangshan,Dawangshan,Gushan and Niangniangshan Formations from early to *** these volcanic rocks are rich in alkali,and show the similar patterns in rare earth element(REE) ***,some differences can be found in the trace elements and REE *** study of petrology and REE geochemical characteristics shows that these rocks are derived from the underplating of the lithospheric mantle and are contaminated by crustal materials,undergo AFC process during the magmatic evolution.

关键词： rare earth elements porphyrite-type iron deposit Ningwu volcanic basin mantle-derived magma assimilation fractional crystallization

Petrology and geochemical characteristics of Precambrian granitic basement complex rocks in the southernmost part of North-Central Nigeria

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Chinese Journal Of Geochemistry 2009年第4期28卷 377-385页

作者： Obiora S.C. Ukaegbu V.U. National Geophysical Research Institute Geological Studies DivisionUppal Road Hyderabad-500007 India Department of geology University of NigeriaNsukka Nigeria Department of geology University of Port HarcourtPort Harcourt Nigeria

The Precambrian basement complex in the southernmost part of North-Central Nigeria is underlain by migmatitic banded gneisses, granitic intrusions and dykes of dolerite, rhyolite porphyry and pegmatite. The rocks are generally felsic, containing modal and normative hypersthene, as well as normative corundum. The basement complex has experienced high-grade regional metamorphism as indicated by the presence of hypersthene and plagioclase of andesine composition. Anatectic melting is suggested by the occurrence of ptygmatic folds, folded gneissose foliation, numerous quartzo-feldspathic veins and lenses of dark-colured, micaceous schistose rocks. Geochemically, the rocks have magnesian, calc-alkalic and strongly peraluminous characteristics. Their overall characteristics suggest derivation from progressive (fractional) partial melting of pelitic rocks during high-grade regional metamorphism, possibly associated with intense hydrothermal activities. The magnesian characteristics reflect close affinity to relatively hydrous, oxidizing melts and source regions in settings broadly related to subduction.

关键词：岩石地球化学特征前寒武纪基底尼日利亚花岗岩中央区域变质作用流纹斑岩叶状结构

Geospatial approach to elucidate anomalies in the hierarchical organization of drainage network in Kuttiyadi River Basin, Southern India

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Frontiers of Earth Science 2022年第3期16卷 786-797页

作者： Thulasi Veedu SWETHA Girish GOPINATH Arun BHADRAN Arjun P Department of geology and Environmental Science Christ CollegeKerala 680125India Geomatics division Centre for Water Resources Development and ManagementKerala 673571India Department of Climate Variability and Aquatic Ecosystems Kerala University of Fisheries and Ocean StudiesKerala 682508India Earthquake geology division Geological Survey of IndiaNER Shillong 793014India

An assessment of anomalies in the hierarchical organization of the drainage network in the Kuttiyadi River Basin(KuRB),Kerala,has been performed by considering various morphometric parameters such as bifurcation index(R),hierarchical anomaly index(Δa),hierarchical anomaly density(ga),and stream gradient index(SL)in a geographical information system(GIS)***,a digital elevation model(DEM)of the area has been generated from Cartosat stereo pair data at 2.5-m *** computed quantitative information about drainage characteristics reveals the highest drainage anomaly is observed in sub-watersheds(SW)III and *** is observed that neo-tectonic activity caused the development of younger stage drainage patterns of structural controls in the sub-watersheds of this river *** tectonic activityinduced diffusion,high energy fluvial erosion,and anthropogenic interferences altered the hierarchical organization of the drainage network of the sub-watersheds in mature to old stages of geomorphic *** results of finding validated with asymmetry factor and ratio of the hierarchical index(Δa)with hierarchical anomaly number(A),bifurcation index(R),direct bifurcation ratio(Rdb),stream gradient index(SL),and denudation index(logTu).From the denudation index analysis,the sediment yield of the river basin is identified as 0.67 t·km^(−2)·yr^(−1).Moreover,the asymmetric factor(AF)in the KuRB shows the imprints of Paleo−Neo Proterozoic crustal tilting toward a NNW−SSE direction.

关键词： river basin hierarchical anomaly bifurcation index stream gradient index denudation index Cartosat-1 DEM