Petrogenesis of granitic rocks of the Jabal Sabir area,South Taiz City,Yemen Republic

The Tertiary granitic intrusive body(～21 Ma) of the Jabal Sabir area was emplaced during the early stages of the Red Sea opening.This intrusive body occupies the southern sector of Taiz City.It is triangular in shape,affected by two major faults,one of which is in parallel to the Gulf of Aden,and the other is in parallel to the eastern margin of the Red Sea coast.The petrogenesis of such a type of intrusion provides additional information on the origin of the Oligo-Miocene magmatic activity in relation to the rifting tectonics and evolution of this part of the Arabian Shield.The granitic body of Jabal Sabir belongs to the alkaline or peralkaline suite of A-type granites.It is enriched in the REE.The tight bundle plot of its REE pattern reflects neither tectonism nor metamorphism.This granite body is characterized by high alkali(8.7%-10.13%),high-field strength elements(HFSE),but low Sr and Ba and high Zn contents.The abundance of xenoliths from the neighboring country rocks and prophyritic texture of the Jabal Sabir granite body indicate shallow depths of intrusion.The major and trace elements data revealed a fractional crystallization origin,probably with small amounts of crustal contamination.It is interpreted that the Jabal Sabir intrusion represents an anorogenic granite pertaining to the A-type,formed in a within-plate environment under an extensional tectonic setting pertaining to rift-related granites.     

西南三江杂岩带景洪南部地区晚泥盆世火山岩的发现及意义

本文对西南三江地区景洪南部新发现的晚泥盆世英安质火山岩进行了系统的锆石U-Pb年龄、Hf-O同位素以及全岩地球化学研究。测年结果显示,该英安质火山岩形成于362.3±3.4Ma。火山岩的SiO₂含量为62.87%~66.29%,MgO含量为2.15%~2.49%,Mg^#值为44~47,富集Na₂O（4.77%~5.51%）,高Na₂O/K₂O比值（2.1~3.3）,低Y（12.5×10^-6~15.3×10^-6）和Yb（1.38×10^-6~1.70×10^-6）,具有高硅埃达克岩的地球化学特征,表明它们由俯冲的洋壳部分熔融而成。低的锆石ε_Hf（t）（+0.87~+3.27）,相对较高的锆石δ¹⁸O（6.31‰~7.64‰）,以及高的全岩Th/Yb（4.86~7.78）和（La/Sm）_N（3.62~4.56）比值,指示岩浆中混染了大洋沉积物或混入了大洋沉积岩起源的熔体。综合区域岩浆岩和沉积岩资料,本文认为南澜沧江带晚泥盆世时经历了板片的俯冲,该俯冲作用很可能代表的是由大中河、大平掌火山岩以及火山块状硫化物矿床（VHMS）指示的弧后洋盆的俯冲消减过程。

     

Palaeomagnetic investigations of the tertiary and quaternary igneous rocks: IV The tertiary volcanic rocks of the Tokaji mountains,Hungary

Measurements are reported from samples collected at twenty three sites in the Tokaj mountains of north-eastern Hungary. The simplest interpretation of the results is in terms of geomagnetic field reversals, for there is no petrological or magnetic evidence of self reversal or of correlation of oxidation state and magnetic sign. Four magnetic zones satisfy the minimum stratigraphic requirements, speculative use of these zones against theHeirtzler et al. magnetic time scale as a control suggests locating the Miocene-Pliocene boundary at 11.75 my. However it seems probable that much of the lower Sarmatian is not represented in the Tokaj samples, although the scatter of individual readings suggest secular variation is averaged out. The virtual pole position at 70.4 W, 82.8 N is not significantly different from the theoretical dipole field.

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Zusammenfassung Es wird über paläomagnetische Messungen an ungarischen Gesteinen berichtet, die von 23 Punkten in den Tokajer Bergen stammen.Die Ergebnisse werden als magnetische Feldumkehrungen gedeutet, da sich weder für Selbstumkehrungen noch für Beziehungen zwischen den jeweiligen Oxidationszuständen der Ilmenite und Titanomagnetite und den magnetischen Daten Anhaltspunkte ergeben haben.Vier magnetische Zonen entsprechen dieser stratigraphischen Abfolge; ein möglicher Vergleich dieser Zonen mit der magnetischen Zeitskala vonHeirtzler u. a. als Kontrolle legt die Vermutung nahe, die Miozän-Pliozän-Grenze mit 11,75 Millionen Jahren anzugeben.Einerseits ist es wahrscheinlich, daß das Untere Sarmat durch die Tokajer Vulkanite nicht vollständig erfaßt wird, andererseits kann eine Säkular-Variation als Deutungsmöglichkeit wahrscheinlich ausgeschlossen werden.Die virtuelle Pol-Position mit 70.4 W, 82.8 N weicht nicht bedeutend vom theoretischen Dipol-Feld ab.

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Résumé Des mesures paléomagnetiques ont été effectuées sur des roches hongroises qui proviennent de 23 endroits des montagnes TokaÏ.Les résultats sont interprétés comme des inversions du champ magnétique car il n'y a pas de raisons d'admettre ni d'auto-inversion ni de rapports entre les états d'oxidation des ilménites et des titanomagnétites et les données magnétiques.Quatre zones magnétiques correspondent à cette suite stratigraphique; une comparaison possible de ces zones avec l'échelle du temps deHeirtzler et al. comme contrÔle laisse supposer que la limite Miocène-Pliocène se situe à 11.75 millions années.Il est probable d'une part qu'une grande partie du Sarmatien inférieur n'est pas représentée par ces roches volcaniques de TokaÏ, d'autre part qu'une variation séculaire comme un interprétation possible peut Être exclue avec grande probabilité.La position virtuelle du pÔle avec 70.4 ouest, 82.8 nord n'est pas très différente du champ théorique du dipole.

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, 23 , . , . . , , . , . Heirtzler'a, , , - 11,75 . — , , , . 70,4 W, 82,8 N .

     

中国海相碳酸盐岩评价中有关有机质丰度下限的几点讨论

综述了中国海相碳酸盐岩有机质下限研究的若干进展,认为针对不同需求,应提出碳酸盐岩烃源岩最低下限、有效烃源岩下限、战略选区下限3个不同的下限标准.高成熟碳酸盐岩原始有机质丰度恢复一直存在争议,根据生烃动力学,结合热史,可实现原始有机质总量的恢复.碳酸盐岩中泥质与有机质丰度、排烃能力是否相关仍存在争论,认为碳酸盐岩中泥质的作用仍有待进一步研究.     

中国海相碳酸盐岩评价中有关有机质丰度下限的几点讨论

综述了中国海相碳酸盐岩有机质下限研究的若干进展,认为针对不同需求,应提出碳酸盐岩烃源岩最低下限、有效烃源岩下限、战略选区下限3个不同的下限标准。高成熟碳酸盐岩原始有机质丰度恢复一直存在争议,根据生烃动力学,结合热史,可实现原始有机质总量的恢复。碳酸盐岩中泥质与有机质丰度、排烃能力是否相关仍存在争论,认为碳酸盐岩中泥质的作用仍有待进一步研究。     

羌塘赤布张错地区新生代火山岩研究

根据K-Ar同位素年代学研究成果,将赤布张错新生代火山活动划分为3期:第Ⅰ期(40.1~35.1Ma)火山喷发较弱,形成小范围分布的细粒安粗岩和斑状粗面岩;第Ⅱ期(26.5~17.6Ma)火山喷溢最为强烈,形成大面积厚层黑色气孔状安粗岩;第Ⅲ期(5.5~4.61Ma)由潜火山作用形成球粒状、斑状粗面岩岩丘。新生代火山岩系包括高钾钙碱性系列和钾玄岩系列,高钾钙碱性火山岩形成于始新世,属于壳源岩浆系列;钾玄岩系火山岩形成于中新世-上新世,属于幔源岩浆系列。由老到新,岩石系列由高钾钙碱性系列→钾玄岩系列演化,岩性由安粗岩→粗面岩演化。     

Strongly undersaturated Tertiary volcanic rocks from the Kangerdlugssuaq area, east Greenland

Erratic blocks from the interior of Kangerdlugssuaq fjord are described with chemical analyses and microprobe data for their constituent minerals. A strongly peralkaline phonolite, unlike any previously known from the province, shows that some magmas which precipitated alkali feldspar, nepheline and amphibole (magnesio-katophorite) differentiated along a trend towards increasing peralkalinity, although this trend is unknown in the nearby plutons. Feldspar-free nephelinite and less undersaturated limburgite are also encountered, which apparently provided a petrographic link between the strongly undersatrated ultramafic rocks recently discovered in the area and the alkali basalts of Prinsen af Wales Bjerge.

Recognition of these rock types provides further important analogies with the plume-generated triple junctions of the African Rift and affords samples approximating closely to the compositions of the more unusual magmas of the area.     

Platinum-group element geochemistry of mafic rocks from the Dongchuan area,southwestern China

Mafic intrusions and dykes are well preserved in the Yinmin and Lanniping districts, located within the western margin of the Yangtze Block, SW China. Although these mafic rocks from the two areas formed during different periods, they share similar ranges of PGE concentration. Most of the Yinmin gabbroic dykes contain relatively high PGE concentrations (PGEs = 13.9–87.0 ppb) and low S contents (0.003 %–0.020 %), higher than the maximum PGE concentrations of mafic magmas melting from the mantle. Two exceptional Yinmin samples are characterized by relatively low PGE (PGEs = 0.31–0.37 ppb) and high S (0.114 %–0.257 %) contents. In contrast, most samples from the Lanniping gabbroic intrusion have low PGE concentrations (PGEs = 0.12–1.02 ppb) and high S contents (0.130 %–0.360 %), except that the three samples exhibit relatively high PGE (PGEs = 16.3–34.8 ppb) and low S concentrations (0.014 %–0.070 %). All the Yinmin and Lanniping samples are characterized by the enrichment of PPGE relative to IPGE in the primitive-mantle normalized diagrams, and the high-PGE samples exhibit obvious Ru anomalies. This study suggests that during the ascent of the parental magma, removal of Os–Ir–Ru alloys and/or chromite/spinel leads to high Pd/Ir ratios and Ru anomalies for the Yinmin high-PGE samples and relatively lower Pd/Ir ratios and Ru anomalies for the Lanniping low-PGE samples. We propose that the magmas parental to the Yinmin gabbroic dykes are initially S-unsaturated, and subsequently, minor evolved magma reached sulfur saturation and led to sulfide segregation. Although the Lanniping parental magmas are originally not saturated in S, the high Cu/Pd ratios (3.8 × 10⁴ to 3.2 × 10⁶) for most of the Lanniping samples indicate the S-saturated state and sulfide segregation. A calculation shows that the PGE-poor magmas might have experienced 0.01 %–0.1 % sulfide segregation in the magma chamber. Therefore, our study provides a possible opportunity to discover PGE-enriched sulfide mineralization somewhere near or within the Lanniping mafic intrusion.     

Geochemistry of eocene calc-alkaline volcanic rocks from the Kastamonu area,Northern Turkey

Analytical data for Sr, Rb, Cs, Ba, Pb, rare earth elements, Y, Th, U, Zr, Hf, Sn, Nb, Mo, Ni, Co, V, Cr, Sc, Cu and major elements are reported for eocene volcanic rocks cropping out in the Kastamonu area, Pontic chain of Northern Turkey. SiO₂% versus K₂O% relationship shows that the analyzed samples belong to two major groups: the basaltic andesitic and the andesitic ones. High-K basaltic andesites and low-K andesites occur too. Although emplaced on continental type basement (the North Anatolian Crystalline Swell), the Pontic eocene volcanics show elemental abundances closely comparable with typical island arc calc-alkaline suites, e.g. low SiO₂% range, low to moderate K₂O% and large cations (Cs, Rb, Sr, Ba, Pb) contents and REE patterns with fractionated light and almost flat heavy REE patterns. REE and highly charged cations (Th, U, Hf, Sn, Zr) are slightly higher than typical calc-alkaline values. Ferromagnesian elements show variable values. Within the basaltic andesite group the increase of K%, large cations, REE, La/Yb ratio and high valency cations and the decrease of ferromagnesian element abundances with increasing SiO₂% content indicate that the rock types making up this group developed by crystalliquid fractionation of olivine and clinopyroxene from a basic parent magma. Trace element concentration suggest that the andesite group was not derived by crystal-liquid fractionation processes from the basaltic andesites, but could represent a distinct group of rocks derived from a different parent magma.     

兰坪思茅盆地第三纪矿床有机质特征及其地质意义

兰坪思茅盆地第三纪矿床富含有机质，有机地球化学研究认为，矿床中的有机质片地未成阶段或低级成熟阶段，其分布受中轴断裂带的控制，有机质为少相、陆相的有机沉积物，生物标志显示盆地第三纪成矿为裂谷构造环境。     

宁芜火山岩的地球化学特征及其意义

宁芜早白垩世火山岩由中基性成分组成,与碱性玄武岩比较,火山岩贫Ti,Fe,富K和LREE,Na2O/K2O近似等于1,在SiO2-K2O图中龙王山组的全部和大王山组的大部落入橄榄玄粗岩区域,属于橄榄玄粗岩系列,为富集LILE和水的地幔部分熔融的产物。宁芜火山岩产于板内环境,富钾质岩浆的形成可能与软流圈地幔上涌和岩石圈的伸展－减薄或裂谷作用有关。宁芜火山岩富集大离子亲石元素,亏损高场强元素,Ti,Nb(Ta)具负异常。宁芜火山岩底部的龙王山组和主体大王山组具有不同的地球化学特征：与大王山组相比,前者更富Rb,Ba,K,而相对贫LREE（La,Ce,Nd),Eu,Sr,Isr较高,εNd(t)较低。由于龙王山组层位低,大王山组层位高,不可能解释为分离结晶作用的结果,而只能说明在火山岩喷发的早期阶段（龙王山组）,岩浆穿过陆壳上升过程中与围岩发生过混染作用,从围岩中带入较多的K、Rb,Ba等大离子亲石元素,从而使得Isr较高和εNd(t)较低。龙王山组SiO2-K2O不具相关性也说明陆壳混染的影响。至宁芜火山岩喷发的极盛时期（大王山组）,岩浆与围岩的混染程度降低,Isr和Nd(t)值更接近岩浆的初始组成。据了解,在长江中下游地区有许多晚中生代的埃达克质岩出露,埃达克质岩来自加厚的陆壳底部,需要很高的温度才能使下地壳基性岩发生部分熔融。宁芜一带火山岩的大规模喷出,表明在早白垩世初期该区地幔处于十分活跃的状态,可能有大量橄榄玄粗质岩浆底侵到下地壳底部,烘烤下地壳使之熔融形成埃达克质熔浆。     

辽西北票—义县地区义县旋回火山岩的岩石化学特征

辽西地区是中国中生代火山岩主要分布区之一。义县组分为4个岩性段。义县火山旋回可分为4个亚旋回。第一亚旋回分为4个小旋回。从早期至晚期，义县旋回火山岩逐渐由基性向中基性、中性和酸性演化，火山岩岩石组合为基性岩-中性岩-酸性岩组合，从北票-义县，火山活动显示了由老到新的迁移性。主要氧化物关系表明岩石的SiO2与K2O呈正相关，SiO2与MgO、CaO、FeO Fe2O3呈负相关。TAS图解反映了火山岩较高碱度的总体特征，硅-碱关系图和AFM图解反映了火山岩属于亚碱性系列中的钙碱性系列岩石，在SiO2-K2O关系图上，绝大部分样品落于高钾钙碱性系列区内，少量落于钾玄岩系列区，因此义县旋回火山岩以高钾钙碱性系列岩石为主，部分为钾玄岩系列，表明岩石富钾。义县旋回火山岩具有大陆板内火山岩的基本特征。     

Thermal alteration experiments on organic matter from recent marine sediments in relation to petroleum genesis

Three fractions of organic matter: lipid (benzene:methanol-extractable), humic acid (alkali-extractable) and kerogen (residue) were extracted from a young marine sediment (Tanner Basin, offshore southern California) and heated for different times (5–116 hr) and temperatures (150°–410°C). The volatile (gases) and liquid products, as well as residual material, were then analyzed. On a weight basis, the lipid fraction produced 58% of the total identified n-alkanes, the kerogen fraction 41%, and the humic acid <1%. Whereas n-alkanes produced from lipid show a CPI > 1.0, those produced by thermal alteration of kerogen display a CPI < 1.0. The volatiles produced by heating the lipid and humic acid fractions were largely CO₂ and water, whereas those produced from heated kerogen also included methane, hydrogen gas and small amounts of C₂–C₄ hydrocarbons. A mechanism for hydrocarbon production due to the thermal alteration of organic constituents of marine sediment is discussed.     

川滇黔相邻区碳酸盐岩容矿铅锌矿成矿特征

本文对川滇黔相邻区碳酸盐岩容矿铅锌矿成矿特征进行系统总结,并对区域成矿过程进行讨论。该区碳酸盐岩容矿铅锌矿发育3种矿床类型,主要分布在泸定-荥经-汉源、雷波-金阳-巧家-会东、赫章-威宁-水城和会泽-彝良4个矿集区,震旦系和古生代地层为主要容矿层。铅锌矿形成于3个成矿期和3类构造环境:以黑区-雪区铅锌矿床为代表的喷流沉积型(SEDEX型),形成于早寒武世海底地震同生断裂环境;以会泽矿床为代表的与侵入作用有关的碳酸盐岩容矿铅锌银矿床类型(IRCH Pb-Zn-Ag型),形成于晚三叠世前陆早期局部引张环境;以大梁子和天桥矿床为代表的密西西比河谷型(MVT型),形成于前陆晚期冲断挤压环境。与世界其它地方不同,川滇黔相邻区MVT铅锌成矿作用主要发生于早侏罗世。     

Geological characteristics and metallogenic prospect of marine volcanic rock-type copper deposits in eastern Kunlun Mountains area,Xinjiang

The Katelixi Cu-Zn deposit is a marine volcanic rock-type copper deposit discovered for the first time in the Tokuzidaban Group in eastern Kunlun Mountains area. It is hosted in the Lower Carboniferous Tokuzidaban Group volcanic strata. The orebodies are obviously controlled by the strata and their ore-bearing rocks are a suite of greyish-green mafic tuffs, generally parallel-stratiform, stratoid and lenticular in form, occurring in limestone as well as in the contact between limestone and carbon-bearing siltstone. This ore deposit possesses distinct characteristics of marine volcanic rock sedimentaion. The geological, petrochemical and REE characteristics of its occurrence pro-vide strong evidence suggesting that this deposit is of marine volcanic rock sedimention origin, basically identical to those of some typical marine volcanic rock-type copper deposits in Xinjiang and other parts of China. Marine vol-canic rocks are well developed in the Lower Carboniferous Tokuzidaban strata in eastern Kunlun Mountains area. In addition to this deposit, we have also found a number of copper polymetallic ore deposits or occurrences in associa-tion with marine volcanc activities in many places where there is a good metallogenic prospect. A breakthrough in the understanding of ore prospecting and genesis has not only filled up the gap in prospecting this type of ore depos-its in this area, but also is of great significance in directing exploration of this type of ore deposits in this area.     

云南省兰坪县石登—兔峨地区火山岩岩石学特征

石登—兔峨地区上三叠统小定西组火山岩属云南西部澜沧江沿岸三叠系火山岩带的一部分，本文从岩相学、岩石化学和地球化学等多方面对该火山岩特征进行了系统、全面分析，并从理论角度对其形成的大地构造环境进行了判别。结果表明：该火山岩以安山岩为主，玄武岩为次，属钙碱性系列，形成于岛弧大地构造环境。     

大民屯凹陷烃源岩有机质丰度的恢复

烃源岩有机质丰度的恢复具有重要的现实和理论意义。笔者在对比多种方法的基础上,对大民屯凹陷的烃源岩的有机质丰度进行了恢复。     

Geochemical Characteristics of Cenozoic Basaltic High-K Volcanic Rocks from Maguan Area, Eastern Tibet

The major element, trace element and Nd-Sr isotopic composition of Cenozoic basaltic volcanic rocks from the Maguan area, eastern Tibet, indicates that the volcanic rocks are enriched in alkalis, especially K (K2O up to 3.81%) and depleted in Ti (TiO2 = 1.27%-2.00%). These rocks may be classified as two groups, based on their Mg# numbers: one may represent primary magma (Mg# numbers from 68 to 69), and the other, the evolved magma(Mg# numbers from 49 to 57). Their REE contents are very high (∑REE = 155.06-239.04μg/g). Their REE distribution patterns are of the right-inclined type, characterized by LREE enrichment [(La/Yb)N =12.0-19.2], no Ce anomaly (Ce/Ce*=1.0), and weak negative Eu anomaly (Eu/Eu*=0.9). The rocks are highly enriched in Rb, Sr and Ba (59.5-93.8μg/g, 732-999 μg/g, and 450-632 g/g, respectively), high in U and Th (1.59-2.31μg/g and 4.73-8.16 μg/g, respectively), and high in Nb, Ta, Zr and Hf (70-118 μg/g,3.72-5.93 μg/g, 215-381 μg/g, and 5.47-9.03 μg/g, respectively). In the primitive mantle-normalized incompatible element spidergram, Nb, Ta, Zr, Hf and P show positive anomalies, whereas Ba, Ti and Y show negative anomalies. The 87Sr/86Sr ratios range from 0. 704029 to 0.704761; 143Nd/144Nd from 0. 512769 to 0. 512949; and εNd from 2.6 to 6.1. These geochemical features might suggest that the potential source of the basaltic high-K volcanic rocks in the Maguan area is similar to the OIB-source mantle of Hawaii and Kergeulen volcanic rocks.     

Occurrence of Highly Mature Organic Matter in Marine Black Shale Petroleum Source Rocks of Basal Cambrian from Northern Tarim Basin, China

More and more evidence indicates that organic matter (OM) in immature organicrich sediments and sedimentary rocks is chemically adsorbed onto the outer surfaces of minerals and into interlayer (inner) surfaces of smectitic clay minerals in the form of amorphous molecular-scale carbon. But there have been few reports about the occurrence of highly mature OM in marine black shales ( petroleum source rocks ). The occurrence of highly mature OM in the black shales of basal Cambrian from northern Tarim Basin is studied in this paper. Based on the comprehensive analyses of total organic carbon contents (TOC) , maximum thermolysis tempera tures ( Tmax ) of OM, mineral surface areas (MSA) ,and scanning electronic microscopic (SEM) and transmission electronic microscopic (TEM) observations of the black shales, it is concluded that the highly mature OM in the marine black shales of the basal Cambrian from northern Tarim Basin occurs in particulates ranging in size from 1 to 5 μm in diameter. Through the contrast of the occurrence of the highly mature OM in the black shales with that of the immature ones in modern marine continental margin sediments, some scientific problems are proposed, which are worth to study further in detail.     

河北沽源-多伦地区中生代含铀火山岩地球化学

沽源和多伦地区是燕辽多金属成矿带的重要组成部分,中生界主要发育上侏罗统白旗组、张家口组,下白垩统大北沟组和花吉营组.张家口组火山岩分布广、厚度大,是铀(钼)矿床的主要含矿主岩.中生代火山岩属于钙碱性系列,化学成分富硅、偏碱,δ值1.17~7.60.稀土元素特征反映火山岩有壳幔混合和壳源改造两种成因.火山岩形成于弱造山环境,其年龄与库拉-太平洋板块向亚洲板块俯冲的时间吻合.张家口组酸性火山岩具有我国相山产铀火山杂岩富硅、富钾,铕极亏损的地球化学特征.