Electronic structures of MCO (M = Nb, Ta, Rh, Ir, Pd, Pt) molecules by density functional theory

Equilibrium geometries, vibrational frequencies, and dissociation energies of the transition metal carbonyls MCO (M = Nb, Ta, Rh, Ir, Pd, Pt) were studied by use of diverse density functional methods B3LYP, BLYP, B3P86, B3PW91, BHLYP, BP86, and PBE1PBE. It was found that the ground electronic state is (6)Sigma(+) for NbCO and TaCO, (2)Sigma(+) for RhCO,(2)Delta for IrCO, and (1)Sigma(+) for PdCO and PtCO, in agreement with previous theoretical studies. The calculated properties are highly dependent on the functionals employed, in particular for the dissociation energy. For most of the molecules, the predicted bond distance is in agreement with experiments and previous theoretical results. BHLYP is the worst method in reproducing the experimental results compared with the other density functional methods for the title molecules.

Determination of Nb and Ta in Nb/Ta minerals by inductively coupled plasmas optical emission spectrometry using slurry sample introduction

The determination of Nb and Ta in Nb-Ta minerals was accomplished by slurry nebulization inductively coupled plasma optical emission spectrometry (ICP-OES), using a clog-free V-groove ceramic nebulizer. Samples were first wet-ground to appropriate particle sizes with narrow size distribution and 90% of the particles in the slurry were smaller than 2.32 mu m in diameter. Subsamples were then dispersed in pH 9 aqueous solutions, and agitated in an ultrasonic bath for 15 min prior to analysis. Due to the lack of slurry standards matching well with the samples, calibration was simply carried out using aqueous solution standards. Results were compared with those obtained from a conventional fusion decomposition procedure and acid digestion procedures and a good agreement between the measured and referred values was obtained. The technique provided a good alternative for the rapid determination of Nb and/or Ta in their corresponding minerals.

V、Nb、Ta对促进Bi系超导体中2223相生成作用研究

自发现BiSrCaCuO超导体以来,为了稳定2223高T_C相结构、增加其在超导体中的含量,在该体系中引入掺杂元素Pb被公认是最有效的方法。我们系统研究了V~(5+)、Nb~(5+)、Ta~(5+)高价离子的单独掺入Bi系中对

可见光响应光催化剂K4Ce2M10O30（M=Ta, Nb）及其光解水特性的研究

氢能已被广泛认为是最具有潜力解决能源危机和环境问题的理想替代能源之一，其开发备受各个领域科学家的重视，更是从根本上解决环境地球化学工作者的主要目标：对已被破坏的环境和生态进行修复以及对可能破坏环境与生态的人类活动进行干预和指导。在众多的氢能开发手段中，利用太阳能光催化分解水制取氢气是一种兼顾能耗、资源和环境的最为理想和最有前途的氢能开发手段之一。在光催化分解水过程中，最为首要的研究内容就是开发具有适宜能带结构能响应可见光，稳定地、高量子效率地光解水的固相半导体光催化剂。 本论文中，通过高温固相反应合成了呈四方晶系钨青铜结构的半导体光催化剂K4Ce2M10O30(M=Ta, Nb)，吸收边分别达到580 nm (M＝Ta) 和690 nm (M＝Nb)，对应带隙为2.2 eV和1.8 eV。可见光下（λ> 420 nm）光催化分解H2O产生H2和O2的活性表明它们不仅有适宜的带隙响应可见光，并且其价带和导带位置能满足完全分解水的电化学电位需要。在担载Pt、RuO2以及NiO（NiOx）等助催化剂对产氢性能有显著的提高。同时以乙醇钽和草酸铌可溶性前驱体，分别通过溶胶凝胶法（Sol-gel）和聚合物络合法(Polymerizable Complex)制备了K4Ce2Ta10O30和K4Ce2Nb10O30。通过湿法化学合成的光催化剂显示了更高的光催化活性，并且通过PC法制备的K4Ce2Nb10O30更是实现了在大于300 nm 的光辐射下完全分解纯水产生摩尔比为约2:1 的H2和O2。 通过高温固相反应得到Nb取代K4Ce2Ta10O30中部分晶格Ta形成的单相无限固溶体系列K4Ce2Ta10-xNbxO30（x=0~10）是结构一致的同系物，吸收边介于540 nm～710 nm 之间，并且随着x的增加，吸收边依次红移，光催化产氢活性依次降低，但是x=2，5，8时的产氧活性比x=0和10的高，光催化活性的差异主要源于它们光吸收特性和能带结构的差异。基于密度范函理论DFT的第一性原理计算结果表明，光催化剂K4Ce2M10O30(M=Ta, Nb)的能带结构为：导带主要由Ta 5d (Nb 4d)组成，处于高能级的电子未占据态的Ce 4f 与其有很明显的重迭，但由于其高度局域特性，不能很好地参与光生电子在导带的传导，从而其对光催化活性的贡献很小，而价带则由O 2p与Ta 5d (Nb 4d)以及电子占据态的Ce 4f杂化轨道组成。同时通过高温固相反应合成了系列含稀土元素的光催化剂K4Re2M10O30(Re=La, Ce, Nd, Sm, Y; M=Ta, Nb)，通过对它们及其前驱体氧化物的光吸收特性以及电子结构的第一性原理计算研究，合理的解释了只有当Ln＝Ce时才具有可见光响应特性的微观机理。

Eu~(3+)激活的LaNb(Ta)复合卤氧化物的合成和光谱特性

采用真空气体输运技术制备了Eu0 .0 6La0 .94 M2 O6X(M =Nb ,Ta ;X =Cl,Br) ,测定了它们的晶体结构及光谱 ,研究了其光谱性质与晶体结构的关系 ,不同金属阳离子和卤素配体对铕光谱性质的影响及其变化规律。

Determination of rare and rare earth elements in soils and sediments by ICP-MS using Ti(OH)(4)-Fe(OH)(3) co-precipitation preconcentration

A method was developed for the determination of trace and ultratrace amounts of REE. Cd. In. Tl. Th. Nb, Ta. Zr and Hf in soils and sediments. With NaOH-Na2O2 as the flux. Ti(OH)(4)-Fe(OH)(3) co-precipitation as the preconcentration technique and inductively coupled plasma mass spectrometry (ICP-MS) for measurement, the whole procedure was concise and suitable for batch analysis of multi-element solutions. An investigation was carried out of the Ti(OH)(4)-Fe(OH)(3) co-precipitation system, and the results obtained showed that the natural situation of Ti tightly coexisting with Nb. Ta, Zr and Hf in geological samples plays a very important role in the complete co-precipitation of the four elements. The accuracy of this procedure was established using six Chinese soil and sediment certified reference materials (GSS and GSD). and the relative errors between the found and certified values were mostly below 10%.

Bond-charge calculation of nonlinear optical susceptibilities of LiXO3 type complex crystals

Second order nonlinear optical (NLO) tensor coefficients of LiXO3 (X = I, Nb, Ta) type crystals have been evaluated on the basis of the dielectric theory of complex crystals and the modified bond charge model. The current method is capable of calculating single bond contributions to the total second order NLO susceptibility. The tenser values thus calculated agree well with experimental data. By introducing the subformula equation and the concept of the effective charge of one valence electron, we are able to successfully treat such complex crystals as LiXO3 type compounds. In addition, the bond charge expression is modified to a more reasonable form for complex crystals. (C) 1998 Elsevier Science B.V.

VB族元素掺杂对YBa_2Cu_3O_(7-y)电子结构的影响

合成了YBa_2Cu_(3-x)M_xO_(7-y)(M=V,Nb,Ta;x-0.0～0.7)高温超导体。X-射线粉末衍射分析表明,x≤0.6时,体系仍然是正交结构,没有发生正交到四方的相变。体系的晶胞参数随x的不同而异。体系的电阻率和Hall系数随x的增加而逐渐增加,它们的载流子浓度和载流子迁移率却随x的增加而下降。这说明VB族元素的置換影响了YBa_2Cu_3O_(7-y)的电子结构。用晶体场理论对体系的电子结构作了解释。

Geochemical and isotopic characteristics of volcanic rocks from the northern East China Sea shelf margin and the Okinawa Trough

Volcanic rocks both from the northern East China Sea (NECS) shelf margin and the northern Okinawa Trough are subalkaline less aluminous, and lower in High Field Strength Elements (HFSE). These rocks are higher in Large Ion Lithophile Elements (LILE), thorium and uranium contents, positive lead anomalies, negative Nb-Ta anomalies, and enrichment in Light Rare Earth Elements (LREE). Basalts from the NECS shelf margin are akin to Indian Ocean Mid-Ocean Ridge Basalt (MORB), and rhyolites from the northern Okinawa Trough have the highest Pb-207/Pb-208 and Pb-208/Pb-204 ratios. The NECS shelf margin basalts have lower Sr-87/Sr-86 ratios, epsilon(Nd) and sigma O-18 than the northern Okinawa Trough silicic rocks. According to K-40-Ar-40 isotopic ages of basalts from the NECS shelf margin, rifting of the Okinawa Trough may have been active since at least 3.65-3.86 Ma. The origin of the NECS shelf margin basalt can be explained by the interaction of melt derived from Indian Ocean MORB-like mantle with enriched subcontinental lithosphere. The basalts from both sides of the Okinawa Trough may have a similar origin during the initial rifting of the Okinawa Trough, and the formation of basaltic magmas closely relates to the thinning of continental crust. The source of the formation of the northern Okinawa Trough silicic rocks was different from that of the middle Okinawa Trough, which could have been generated by the interaction of basaltic melt with an enriched crustal component. From the Ryukyu island arc to East China, the Cenozoic basalts have apparently increasing trends of MgO contents and ratios of LREE to Heavy Rare Earth Elements (HREE), suggesting that the trace element variabilities of basalts may have been influenced by the subduction of the Philippine Sea plate, and that the effects of subduction of the Philippine Sea plate on the chemical composition of basaltic melts have had a decreasing effect from the Ryukyu island arc to East China.

南海新生代碱性玄武岩的特征及其地球动力学意义

南海是西太平洋最大的边缘海之一，位于欧亚板块、印-澳板块以及太平洋板块之间。南海海底扩张停止(15.5Ma, Briais et al., 1993) 后的板内火山作用，影响着中国南部、中南半岛、大洋基底和分裂的微大陆片段的广大地区。对南海新生代玄武岩进行地球化学研究，不仅对于理解南海板内火山作用的深部地幔过程有着重要意义，而且对南海形成演化及含油气盆地形成的深部动力学机制有着深远意义。 南海新生代玄武岩K-Ar/Ar-Ar年龄为3.8-7.9Ma, 表明为晚中新世以来的岩浆活动产物，与周边地区的碱性火山岩在年龄上的一致性。岩石学特征表明，南海新生代玄武岩的矿物组合为橄榄石、单斜辉石、斜长石，与特征的碱性玄武岩的矿物组合一致。由橄榄石所计算的南海底潜在地幔温度(Tp)平均值为1661℃, 暗示南海地区下的地幔可能存在热量异常，为海南地区存在地幔柱的观点提供了证据。单斜辉石富钙、钛，由单斜辉石-熔体平衡温压计计算的岩浆房深度分别为：碱玄岩岩浆房深度约49km（对应压力为1.46～1.48 GPa）；粗面玄武岩岩浆房约25km（对应压力为0.76 GPa）；玄武岩岩浆房约15km（对应压力为0.44GPa）。由碱玄岩→粗面玄武岩→玄武岩，平衡温度(K)依次降低:从1535～1498→1429→1369。由斜长石微晶所计算的岩浆喷出地表的温度为989℃。 主量元素特征表明，岩石类型主要为碱玄岩，有少量的粗面玄武岩和玄武岩，属于碱性系列。微量元素方面，大离子亲石元素(LILE)以及高场强元素（HFSE）特别是Nb、Ta、Ti、Y等元素均呈现富集现象，Yb、Sc、Sr以及K、U、Th等生热元素相对亏损，微量元素及稀土元素分布岩石类似板内OIB微量元素的全球平均值。同位素地球化学研究表明，源区存在两个混合端员并具Dupal Pb异常：一个为DMM，位于软流圈或岩石圈地幔中；另一个为EM2源区，可能来自位于核-幔边界处的海南地幔柱而非大陆底岩石圈地幔。研究表明，南半球Dupal异常不存在全球范围内的地区专属性，本区存在的Dupal异常与南半球Dupal异常可能不存在联系。在南海新生代玄武岩的成因过程中，海南地幔柱在为岩石圈地幔的部分熔融作用提供所需的热量同时，也在物质上作出了贡献。南海盆新生代碱性玄武岩由不同程度的部分熔融作用，以及岩浆在上升期间或者在高位岩浆房中的橄榄石等矿物分离结晶作用所形成，同时还可能发生了堆晶作用。构造环境判别表明，玄武岩浆在上升到地表过程中几乎未受到地壳混染。 南海新生代玄武岩的地球化学研究表明，在玄武质岩浆的深部地幔演化过程中，海南地幔柱可能起着重要的作用。通过引入海南岛地幔柱这个概念，本文建立了一个新的有关南海形成演化的初步的概念性模型：（1）50-32Ma，印度洋板块-欧亚板块碰撞及其所导致的太平洋板块后退的综合效应为南海地区提供了一个伸展环境，此伸展环境为地幔柱物质的上升提供了通道；（2）32-21Ma，当地幔柱柱头到达软流圈时, 通过侧向物质流开始同扩张中心发生相互作用，促进了南海的扩张，并在26-24Ma期间发生了洋脊重新就位事件，使扩张中心从原来的18°N附近(即现今西北海盆的中心)调整到15.5°N附近（即现今的东部亚盆）；（3）21-15.5Ma, 随着地幔柱效应的逐渐增强，热点-洋脊相互作用越来越强烈，在大约21Ma发生了洋脊的再次重新就位事件，诱发了西南海盆的扩张；（4）15.5-现在，由于印澳板块前缘与巽他大陆碰撞，使得南海大约在15.5Ma停止扩张,并沿着南沙海槽及吕宋海沟向菲律宾岛弧及巴拉望地块之下俯冲，而南海热点继续活动，在地表处直到第四纪还有碱性玄武岩喷出。

青岛晚白垩世岩石圈结构特征：劈石口晚白垩世基性脉岩及其捕虏体提供的证据

The occurrence of Late Cretaceous mafic dykes and their entrained peridotite and granulite xenoliths as well as clinopyroxene xenocrysts in the Qingdao region provide us a precious opportunity to unveil the nature and characteristics of the Late Mesozoic lithospheric mantle and lower crust beneath the Jiaodong region, and the change of the magma sources. These studies are of important and significant for understanding the lithospheric evolution in the eastern North China Craton. There were two periods of magma activities in Late Mesozoic in Qingdao Laoshan region, one was around 107Ma in the Early Cretaceous and the other around 86Ma in the Late Cretaceous according to the whole rock K-Ar age determination. The Early Cretaceous mafic dykes and the Late Cretaceous mafic dyke (i.e. Pishikou mafic dike) have completely different geochemical characteristics. The Early Cretaceous mafic dykes are enriched in LILE, strongly depleted in HFSE (Nb, Ta, Zr, Hf) and characterized by the highly radiogenic Sr and Nd isotopic compositions. These geochemical features indicate that the Early Cretaceous mafic dykes were derived from an enriched lithospheric mantle. In contrast, the Late Cretaceous mafic dyke is enriched in LILE, without HFSE depletion (Nb, Ta, Zr, Hf) and has less radiogenic Nd and Sr isotopic compositions. These geochemical features indicate that the Late Cretaceous mafic dyke was derived from the asthenosphere modified by subducted pelagic sediment contamination. The intrusive age of the Late Cretaceous mafic dyke provides further information for the termination of the lithosphere thinning for the eastern North China Crtaon. Pishikou Late Cretaceous mafic dyke contains abundant peridotitic xenoliths, granulite xenoliths and clinopyroxene xenocrysts. The peridotitic xenoliths can be divided into two types: high Mg# peridotites and low Mg# peridotites, according to their textural and mineral features. The high-Mg# peridotites have high Fo (up to 92.2) olivines and high Cr# (up to 55) spinels. The clinopyroxenes in the high# peridotites are rich in Cr2O3 and poor in Al2O3. The low-Mg# peridotites are typified by low Mg# (Fo <90) in olivines and low Cr# (Cr# <0.14) in spinels. The clinopyroxenes in the low-Mg# peridotites are rich in Al2O3 and Na2O and poor in Cr2O3. These two type peridotites have similar equilibrated temperatures of 950C-1100C. The Clinopyroxenes in the high-Mg# peridotites generally have high and variable REE contents (REE = 5.6-84 ppm) and LREE-enriched chondrite-normalized patterns ((La/Yb)N>1). In contrast, the clinopyroxenes in the low-Mg# peridotites have low REE contents (REE = 12 ppm) and LREE-depleted patterns ((La/Yb)N<1). The textural, mineral and elemental features of the low-Mg# peridotites are similar to those of the low-Mg peridotites from the Junan, representing the newly-accreted lithospheric mantle. However, the mineralogical and petrological features of the high-Mg# peridotites are similar to those of the high-Mg# peridotites from the Junan region, representing samples from the old refractory lithospheric mantle that was strongly and multiply affected by melts of different origins Late Cretaceous mafic dike in the Qingdao region also contains two types of granulite xenoliths according to the mineral constituents: the pyroxene-rich granulites and the plagioclase-rich granulites. Equilibrated temperatures calculated from the cpx-opx geothermometers are in a range of 861C - 910C for the pyroxene-rich granulites and of 847C - 890C for the plagioclase-rich granulites. The equilibrated pressure for the plagioclase-rich granulites is in a range of 9.9-11.7 kbar. Combined with the results of the peridotitic xenoliths, a 40C temperature gap exists between the peridotite and the granulite. The petrological Moho was 33~36 km at depths, broadly consistent with the seismic Moho estimated from the geophysical data. This indicates that there was no obvious crust-mantle transition zone in the Qingdao region in the Late Mesozoic. Pishikou Late Cretaceous mafic dyke entrained lots of clinopyroxene xenocrysts which are characterized by the chemical zoning. According to the zoning features, two types of clinopyroxene xenoliths can be classified, the normal zoning and the revise zoning. The normally-zoned clinopyroxene xenocrysts have LREE-depleted REE patterns in the cores. In contrast, the revisely-zoned clinopyroxenes have LREE-enriched REE patterns in the cores. According to the rim and core compositions of xenocrysts, all the rims are balanced with the host magma. Meanwhile, the origins of the cores were complicated, in which the normally-zoned clinopyroxenes were derived form the lithospheric mantle and some of the reversely-zoned clinopyroxnes were originated from the lower crust. Other revisely-zoned clinopyroxenes had experienced complex geological evolution and need to be further investigated. According to the above results, a simplified lithospheric profile has been established beneath the Qingdao region and a constraint on the nature and characteristics of the lithospheric mantle and lower crust has been made.

俯冲带深部流体特征——以西南天山变质俯冲杂岩为例

The subduction zone is an important site of the fluid activity and recycling of chemical elements. The fluid characteristic of deep subduction zones is a top scientific problem attracting the petrologists, geochemists and tectonists. In this dissertation, the characteristics of fluid activity within a deep subduction zone have been explored on the basis of the studies on the petrography, mineral chemistry, fluid inclusions, geochemistry and metamorphic P–T conditions of the omphacite-bearing high-pressure veins and related hosts from the low-temperature/high-pressure metamorphic belt in southwestern Tianshan, China. Multiple high-pressure veins are exposed in host eclogites and blueschists. The veins are composed predominantly of omphacite, garnet, quartz, and other minerals. Some veins contain cm-sized rutiles. In general, the vein can be divided into three types, the ‘in situ dehydration’ vein, the ‘external transport’ vein and the ‘composite’ vein. The omphacites within the veins and related host rocks contain lots of two-phase or three-phase primary fluid inclusions. The final melting temperature (Tfm) of fluid inclusions varies mainly from -0.6 to -4.3 °C, the homogeneous temperature (Th) varies from 185 to 251 °C, the salinity varies from 1.1 to 6.9 wt.% NaCl equivalent and the density varies from 0.81 to 0.9 g/cm3. The fluids were released under the conditions of T = 520–580°C and P = 15–19 kbar at blueschist facies to eclogite facies transition. The fluids include not only Li, Be, LILE, La, Pb-enriched and HFSE- and HREE-depleted aqueous fluids but also HFSE (Ti-Nb-Ta)-rich aqueous fluids. The complex composed of aluminosilicate polymers and F was the catalyst which had caused the Ti-Nb-Ta to be dissolved into the fluids. During the transport of the LILE-rich and HFSE- and HREE-poor fluids, they can exchange some chemical elements with country rocks and leach some trace elements in some extent. The rutile could be precipitated from the HFSE (Ti-Nb-Ta)-rich aqueous fluids when CO2 was added into the fluids. The host rocks could obtain some elements, such as Ca, Cs, Rb, Ba and Th, from the external fluids. The fluids with complex composition had been released within the deep subduction zone (>50 km) in Early Carboniferous during the subduction of the South Tianshan Ocean under the Yili–Central Tianshan Plate. The results obtained in this dissertation have made new progress compared with the published data (e.g. Tatsumi, 1989; Becker et al., 1999; Scambelluri and Philippot, 2001; Manning, 2004; Hermann et al., 2006; Spandler and Hermann, 2006).

荣成基底片麻岩原岩岩石成因及其构造意义

Extensive high to ultrahigh pressure metamorphic rocks are outcropped in the the Dabie-Sulu UHP orogenic belt. Disputes still exist about for protolith nature of metamorphic rocks, petrogenesis, tectonic setting, and influence on upper mantle during the Triassic deep subduction. In this study, a combined study of petrology, geochemistry, isotope geochemistry and zircon chronology was accomplished for high-grade gneisses in the basement of the ultrahigh-pressure metamorphic Rongcheng terrane to reveal protolith nature and petrogenesis of the gneisses and to disucss the magmatic succession along the northern margin of the Yangtze block in Neoproterozoic. Gneisses in the Rongcheng terrane are characterized by negative Nb, Ta, P and Ti anomalies, relatively low Sr/Y ratios and relatively high Ba/La, Ba/Nb and Ba/Zr ratios, mostly displaying geochemical affinity to Phanerozoic volcanic arc. Neoproterozoic protolith ages (0.7 ~ 0.8 Ga) and Paleoproterozoic average crustal residence time (1.92 ~ 2.21 Ga) favour a Yangtze affinity. The gneisses mostly display characteristics of enrichment of LREE, flat heavy rare earth elements (REE) patterns, moderately fractionation between LREE and HREE and slight negative or positive Eu anomalies, probably reflecting that melting took place in the middle to low crust (26 ~ 33 km), where amphibole fractionated from the melts and/or inherited from source material as major mineral phases in the source area. Sr-Nd isotopic composition of the gneisses supports this conclusion. According to εNd(t) and εHf(t) values, the gneisses can be divided into three groups. Gneisses of group I have the highest εNd(t) and εHf(t) values, corresponding to the range of -6 ~ -3 and -2.9 ~ 13.4, respectively. This suggests obvious influx of depleted mantle or juvenile crust in the formation of protoliths. Gneisses of group II have medium εNd(t) (-9 ~ -7) and εHf(t) values (-15.8 ~ -1.4), corresponding to relatively high TDM2(Nd) (1.99 ~ 2.31 Ga) and TDM2(Hf) (1.76 ~ 2.67 Ga) , respectively. This suggests these gneisses were formed by partial melting of Paleoproterozoic crust. Gneisses of group III have the lowest εNd(t) (-15 ~ -10) and εHf(t) values (-15.8 ~ -1.4), corresponding to the largest TDM2(Nd) (1.99 ~ 2.31 Ga) and TDM2(Hf) ( 1.76 ~ 2.67 Ga), respectively. This indicates that gneisses of group III were formed by remelting of Archean crustal material and further demonstrates existence of an Archean basement probably of the Yangtze affinity beneath the Rongcheng terrane. Gneisses of three groups have also certain different geochemical characteristics. Contents of REEs and trace elements reduce gradually from group I to group III. Zirconium saturation temperatures also show similar tendency. Compared to gneisses of group II and group III, gneisses of group I display geochemical feature similar to extensional tectonic setting, having relatively little influence by the source area. Therefore, geochemical characteristics for gneisses of group I can indictate that the protoliths of the Rongcheng gneisses formed in an extensional rifting tectonic setting. This conclusion is supported by the results of eclogites and gabbros previously reported in the Dabie-Sulu orogenic belt. Statistical results of the protolith ages of the Rongcheng gneisses show two age peaks around ~728 Ma and ~783 Ma with an about 50 Ma gap. Extensive magatism in abou 750 Ma along the northern margin of the Yangtze block can hardly be observed in the Rongcheng terrane. This phenomenon likely suggests discontinuous Neoproterozoic magmatism along the northern margin of the Yangtze block.

乍得西南部中新生代火山作用与盆地演化

Located in the Central and West African, Chad, which is not well geological explored, is characterized by Mesozoic- Cenozoic intra-continental rift basins. The boreholes exposed that, during Mesozoic-Cenozoic times, volcanic activities were intense in these basins, but study on volcanic rocks is very weak, especially on those embedded in rift basins, and so far systematic and detailed work has still no carried out. Based on the project of China National Oil and Gas Exploration and Development Corporation, “The analysis of reservoir condition and the evaluation of exploration targets of seven basins in block H in Chad”, and the cooperative project between Institute of Geology and Geophysics, CAS and CNPC International (Chad) Co. Ltd., “Chronology and geochemistry studies on Mesozoic-Cenozoic volcanic rocks from southwestern Chad Basins”, systematic geochronology, geochemistry and Sr-Nd-Pb isotopic geochemistry studies on volcanic rocks from southwestern Chad basins have been done in the thesis for the first time. Detailed geochronological study using whole-rock K-Ar and Ar-Ar methods shows the mainly eruption ages of these volcanic rocks are Late Cretaceous- Paleogene. Volcanic rocks in the well Nere-1 and Figuier-1 from Doba basin are products of the Late Cretaceous which majority of the K-Ar (Ar-Ar) ages fall in the interval 95-75 Ma, whereas volcanic rocks in the well Ronier-1 from Bongor Basin and the Well Acacia-1 from Lake Chad Basin formed in the Paleogene which the ages concentrated in 66-52Ma. Two main periods of volcanic activity can be recognized in the study area, namely, the Late Cretaceous period and the Paleogene period. Volcanic activities have a general trend of south to north migration, but this may be only a local expression, and farther future studies should be carried on. Petrology study exhibits these volcanic rocks from southwestern Chad basins are mainly tholeiitic basalt. Major- and trace elements as well as Sr-Nd-Pb isotopic geochemistry studies show that the late Cretaceous and the Paleogene basalts have a definitely genetic relationship, and magmas which the basalts in southwestern Chad basins derived from were produced by fractional crystallization of olivine and clinopyroxene and had not do suffered from crustal contamination. These basalts are prominently enriched light rare earth elements (LREE), large-ion lithophile elements (LILE) and high field strength elements (HFSE) and depleted compatible elements. They have positive Ba, Pb, Sr, Nb, Ta, Zr, Hf anomalies and negative Th, U, P,Y anomalies. It is possible that the basalts from southwestern Chad basins mainly formed by mixing of depleted mantle (DM) and enriched mantle (EMⅡ) sources. The late Cretaceous basalts have higher (87Sr/86Sr)i ratios than the Paleogene basalts’, whereas have lower (143Nd/144Nd)i ratios than the latter, showing a significant temporal evolution. The mantle sources of the Late Cretaceous basalts may have more enriched mantle(EMⅡ) compositions, whereas those of the Paleogene basalts are relatively more asthenospheric mantle (DM) components. The mantle components with temporal change observed in basalts from Chad basins were probably correlated with the asthenospheric mantle upwelling and lithospheric thinning in Central and Western Africa since Mesozoic. Mesozoic- Cenozoic Volcanism in Chad basins probably is a product of intra- plate extensional stress regime, corresponded to the tectonic setting of the whole West and Central African during Cretaceous. Volcanism is closely correlated with rifting. As time passed from early period to late, the basaltic magma of Chad basins, characterized with shallower genetic depth, higher density and smaller viscosity, probably indicates the gradual strengthening evolution of the rifting. In the initial rife stage, volcanic activities are absent in the study area. Volcanic activities are basiccally corresponded with the strong extensional period of Chad basins, and the eruption of basalts was slightly lagged behind the extensional period. In the post-rift stage (30-0Ma), these basins shifted to the thermal sag phase, volcanic activities in the study area significantly decreased and then terminated.

内蒙古中部道郎和都格铜多金属矿的地质特征矿床类型及找矿模式研究

Daolangheduge copper polymetallic deposit is located on east edge of Ondor Sum-Bainaimiao metallogenic belt, which is a prospective area of porphyry copper deposit, in Xianghuangqi of central Inner Mongolia. Geotectonically, it occurred in the continental margin accretion belt along the north margin of North China Plate, south of the suture zone between North China Plate and Siberian Plate. The intrusive rocks in this area mainly consist of intermediate-acid magmatic rocks, and the quartz veins, tourmaline veins and the transitional phase are comparatively developed. According to our research, the ore-bearing rock body is mainly quartz diorite while the surrounding rock is mainly biotite granite. Besides, the wall rock alteration are mainly propylitization, pyritization and silicification, which consist of epidotization, actinolitization, chloritzation and so on. The metallic minerals are mainly chalcopyrite and pyrite. In addition, the primary ore is mainly of quartz-chalcopyrite-pyrite type. Above all, Daolangheduge copper polymetallic deposit is suggested to be categorized in the porphyry copper type. With isotopic dating and geochemical research on quartz diorite of ore-bearing rock body, the zircon LA-ICP-MS U-Pb dating of two samples yields an age of 266±2 Ma, falling into the range of late Permian Epoch. It is the first accurate age data in Xianghuangqi area, so it should play a key role in the research of deposit and magmatic rocks in this area. With the major elements and trace elements analysis of 14 samples, the quartz diorite should be among the calc-alkaline series, the geochemical characteristics show higher large-ion lithophile elements of Rb, Sr and LREE, low high-field strength elements of Nb, Ta and high transition elements of Cu, Cr . Also, the REE patterns have negative Eu anomalies. With the same analysis of 4 sample for the biotite granite, the geochemical characteristics show higher Rb, Th,, Zr, Hf and LREE, low Nb, Sm and HREE and Eu has no anomaly. It should be among the calc-alkaline series, over aluminum quality and has characteristics of Adakites. According to isotopic dating and geochemical characteristics of ore-bearing rock body, it is suggested that its materials mainly derived from upper mantle that had fractional crystallization and its magma source region may be affected by fluid metasomatism of paleo-asian ocean. It should be an extensional process of post-orogeny according to regional tectonic evolution. Consequently, because of the decrease of temperature and pressure, the ore forming fluid was raised to surface and mineralized accompanied by magmatic activity which might occur in south of the suture zone. By geological survey, further geophysical and geochemical work is needed. In this area, we have accomplished high precision magnetic prospecting, high density electrical survey, gravity prospecting, soil geochemical prospecting, X-ray fluorescence analyzer prospecting and so on. According to geophysical and geochemical abnormal and surface occurrence, 11 drills are arranged to verification. The type of ores are mainly quartz-chalcopyrite-pyrite ores within 3 drills by drill core logging. Although the grade as well as the scale of already-found Cu deposits are insufficient for industrial exploitation, the mineralization prospect in this region is supposed to be great and the potential in mineral exploration at depth is excellent.