东营凹陷烃类充注与储集层化学成岩作用

分析东营凹陷古近系碎屑岩储集层的矿物微观特征、组合关系及其在沉积剖面上的分布特征、主要成岩作用及其地球化学过程 ,认为控制化学成岩作用的地质 地球化学因素主要包括母岩区的岩性特征、沉积环境与沉积相、地层孔隙水性质的改变、早期方解石的充填作用、烃类充注等 ,其中最重要的是地层孔隙水地球化学条件的变化。重点讨论烃类充注对储集层成岩演化的控制作用 :与未被烃类充注的砂岩相比 ,被烃类充注的砂岩的石英次生加大和钾长石的钠长石化程度要低 ,抑制晚期方解石胶结物的充填 ,长石类及碳酸盐类矿物的溶解十分强烈 ,次生孔隙很发育 ;储集层含油饱和度较低时会促进伊利石生长 ,只有在含油程度较高时伊利石生长才受到抑制。图 4照片 6参

大庆长垣北-断东葡Ⅰ油层组化学成岩作用对砂岩储层孔隙结构的影响

通过对650块砂岩样品铸体薄片偏光显微镜下观察,辅以粘土矿物X-射线衍射分析,电子探针,阴极发光显微照相,电子扫描显微镜,显微图象分析和压汞分析等手段,详细地研究了大庆长垣萨尔图油田北-断东地区葡Ⅰ油层组砂岩储层化学成岩作用与孔隙结构的关系,该区葡Ⅰ油层组砂岩属于湖泊浅水三角洲沉积体系中水下分流平原沉积,碎屑成分复杂,成熟度低,虽然现今埋深为950～1200m,但所经历的化学成岩作用对孔隙结构的改造效果却十分显著,其中体积分数1.1的亮晶方解石胶结作用可以使砂岩中粗喉(10～60"m)下降12.9％,渗透率降低1～2个数量级(/Jm^2),化学溶解作用是提高本区砂岩孔,渗的主要原因之一。它可以使砂岩的粗喉达26.3％,渗透率大于8flm^2。

厦门港滩涂沉积物中铁、锰的早期化学成岩过程

研究了厦门港滩涂沉积物铁锰的化学过程.测定了不同季节沉积物柱样的孔隙度、间隙水盐度、氧化还原电位(E_(pt))、Mn^(2+)、Fe^(2+)的垂直分布,显示了滩涂沉积物由于泥沙的不均匀分布和分带性以及陆源淡水的不规则渗入导致Fe、Mn的化学成岩作用比较复杂;沉积物柱样的多数层次处于中等还原性,间隙水Mn^(2+)在表面层(0～2cm深度)无季节差别出现最高值(E_(pt)下降梯度最大),深于2cm层Mn^(2+)随深度大幅度下降;间隙水Fe^(2+)与Mn^(2+)具有类似的变化趋势,且随着沉积物还原性的增加.MnO_2和Fe_2O_3先后还原与其过程自由能的卞降次序一致.

为什么火成岩地球化学需要地质学、岩石学和矿物学证据约束?

近年来,涌现了大量有关火成岩数值岩石学或化学岩石学的论文。但这不但没有导致科学问题的减少,反而出现了更多难以理解的难题。导致这种困境的主要原因是许多认识缺乏地质学、岩石学和矿物学约束,以及研究人员对火成岩理论研究进展的不关心。岩浆型矿床的成因是一个典型实例。基于此,分析了地球化学数据多解性的原因,介绍了岩浆系统的一般性质,并以四川攀西地区白马铁钛氧化物矿床为例,讨论了利用地质学、岩石学和矿物学证据约束地球化学数据的方法。在此基础之上提出:(1)全岩成分本质上不包含成因信息,相容元素的丰度可以表达岩石的潜在相组成,而不相容元素的丰度则可以表达岩石经历过的流体过程,因而数值岩石学只有得到严格的地质学、岩石学和矿物学约束才具有真实地质意义;(2)大型岩浆型矿床的形成同样需要巨量的含矿流体,透岩浆流体成矿模型可以更合理地解释白马铁钛氧化物矿床的成因。

鄂尔多斯盆地白垩系粘土矿物的分布特征及其沉积-成岩环境意义

系统地分析了鄂尔多斯盆地白垩系粘土矿物的特征及其沉积、成岩环境意义。研究结果表明:白垩系砂岩、泥质岩的粘土矿物组合以I+C+I/S型、I+C型为主,具有高伊利石含量,较高绿泥石、伊/蒙混层矿物含量的粘土矿物组成特点;其中泥质岩粘土矿物主要为陆源碎屑成因,次为沉积成岩过程中形成的自生粘土矿物,而砂岩粘土矿物兼有陆源碎屑成因和沉积成岩过程自生成因的特征;白垩系沉积时气候总体特征为干旱—半干旱,但局部时段发生干—湿气候波动而处于短暂的湿热气候环境;白垩系沉积物源富含长石等硅酸盐矿物,沉积物质主要自北、南、西向盆地内部搬运沉积;白垩系沉积和埋藏成岩过程中水介质整体上具有盐度较高,偏碱性,富K+、Fe2+、Mg2+的特点,且总体上盆地南部水介质中的这些指标都高于北部。

厦门港间隙水碱度和沉积物反应活性

测定了厦门港沉积物间隙水NH^+_4、SO^(2-)_4、pH、AlK、Ept、Ca^(2+)和Mg^(2+)等参量的深度分布,探讨由SO^(2-)_4、NH^+_4、Ca^(2+)和Mg^(2+)浓度计算间隙水AlK的计算式,得出了沉积物成岩分解有机质N/C无素比值在柱样表层为0.16,深层为0.083,间隙水△SO^(2-)_4/△∑CO_2=0.51,通过表层沉积物的缺氧培养,测出了海区沉积物化学成岩反应活性的分布。

Geochemistry of intrusive rock in Dachang tin-polymetallic ore field, Guangxi, China: Implications for petrogenesis and geodynamics

The major element, trace element and rare earth element（REE） of the intrusion rock from the Dachang ore field in Guangxi, China, were analyzed. The results show that the phenocryst（about 15%） and matrix（about 85%） mainly consist of quartz, K-feldspar and plagioclase. The rock is composed of low content of Si and high content of Al2O3, low contents of Ca, Fe2O3, Na, TiO2, etc. The intrusion rock has the medium alkali content, attributing to K-rich type rock; and contains medium to low REE contents, of which light rare earth elements（LREEs） and heavy rare earth elements（HREEs） are highly fractionated, showing a weak negative Ce anomaly and a negative Eu anomaly. These rocks are enriched in LREE, and the large ion lithophytes elements（LILE） are rich in Rb, Sr, and U; the high-field-strength elements（Nb, Th, etc） are relatively depleted. The REE chondrite-normalized patterns are consistent with the overall, roughly indicating their similar characteristics, sources and evolution. The intrusion rock mainly formed during the collisional and within-plate periods.

Chemical Constituents of Hedysarum gmelinii

To study the chemical constituents of Hedysarum gmelinii. Methods Theconstituents were separated and purified by different methods of chromatography, and theirstructures were elucidated by DR, MS and NMR. Results Eight compounds were isolated from Hedysarumgmelinii, including three triteipenoids, two flavonoids and two other compounds. Their structureswere identified as squasapogenol (1), soyasapogenol (2), lupeol (3), 3, 9-dihydroxy coumestan (4),3-hydroxy-9-me-thoxy pterocarpan (5), β-sitosterol (6), palmatic acid (7), and hexadecanoic acid 2,3-dihydroxypropyl ester (8). Conclusion All the compounds have been isolated from this plant forthe first time. Compounds 1 — 4 and 8 were obtained from this genus for the first time. The NMRdata of 1 are reported for the first time.

Rock-forming mechanism of Qingshanjiao intrusion in Dongguashan copper(gold) deposit, Tongling area, Anhui province, China

Dongguashan deposit is a large porphyry-skarn copper（gold） deposit in Tongling ore district. The Qingshanjiao intermediate acid intrusion of Yanshanian had a direct genetic relationship with mineralization. The magma origin, rock-forming dynamic background and rock-forming process were studied, and the rock-forming mechanism of Qingshanjiao intrusion was discussed, based on geological characteristics, detailed observation of petrography and systematic investigation of petrochemistry, trace elements and REE geochemistry characteristics of Qingshanjiao intrusion. The results show that Qingshanjiao rock body belongs to high-K calc-alkaline series with higher LREE elements, Th, Rb and Sr abundance, but depleted in HREE elements, Ba, Nb and Ta. The primary magma originated from the mantle-crust mixtures which were caused by basaltic magma of mantle mixing with syenite magma of partial melting of the lower crust, and the formation environment of Qingshanjiao intrusion was emplaced in the transitional environment from compression to extension. The Harker diagram and hybrid structures of plagioclase and potassium feldspar indicate that the fractional crystallization occurred in the process of magmatic evolution. The petrochemistry, trace elements and REE geochemistry characteristics indicate that the magma was contaminated by crustal material during the rock-forming. These results suggested that the Qingshanjiao intrusion was formed by fractional crystallization and assimilation and hybridization of mantle-crust magma in the transitional environment from compression to extensional.

Petrogenesis of skarn in Shizhuyuan W-polymetallic deposit, southern Hunan,China:Constraints from petrology,mineralogy and geochemistry

Skarn is the main altered rock type and is of great importance to mineralization and ore-prospecting in the Shizhuyuan area of Hunan province, China. Its features of petrography, mineralogy and geochemistry were studied systematically. The results show that the skarn mainly consists of garnet skarn, secondary wollastonite-garnet skarn, tremolite-clinozoisite skarn, and few wolframine garnet skarn, idocrase-garnet skarn and wollastonite skarn with granoblastic texture, granular sheet crystalloblastic texture, and massive structure, disseminated structure, mesh-vein structure, comb structure, and banded structure. And, it is mainly composed of garnet, fluorite, chlorite, hornblende, epidote, tremolite, plagioclase, biotite, muscovite, plagioclase, quartz, idocrase, and calcite and so on. The chemical components mainly include SiO2, Al2O3, Fe2O3, MgO and CaO, and the trace elements and REEs consist of Li, Be, V, Co, Zn, Ga, Rb, Sr, Y, Ce, Nd, Pb and Bi, etc. And, the obvious fractionation exists between LREE and HREE, and it shows typical features of Nanling ore-forming granite for W？Sn polymetallic deposit. Skarn is derived from the sedimentary rock, such as limestone, mudstone, argillaceous rock, and few pelitic strips. It is affected by both Shetianqiao formation strata and Qianlishan granite during the diagenesis, indicating a strong reduction environment. The occurrence of skarn, whose mutation site is favorable to the mineralization enrichment, is closely related to the mineralization and prospecting.

Zircon geochemistry of different intrusive phases of Weiya pluton: implications for magma genesis

The characteristics of hosted magmas and their petrogenesis based on electron microprobe determination of trace element contents in zircons were discussed. Trace element geochemistry of zircons indicates that zircons in both gabbro and quartz syenite have two-generations. Zircons of the first generations are crystallized in the magma chamber, whereas those of the second generations are formed in supercooling environment. The former is richer in Zr, but poorer in U, Th, Hf and Y. Quartz diorite porphyrite contains zircons that can be distinguished into the early and late generations. Compared to the late generation, the early generation is richer in Zr but poorer in U, Th, Hf and Y. No conspicuous disruption of zircon evolution has been found in both biotite monzogranite and fine-grained granite. However, the content of zircon in fine-grained granite is higher in U, Th and Y and lower in Zr relative to biotite monzogranite without significant contrast in mass fraction ratio of ZrO2 to HfO2 ratio. Such differences in zircon geochemistry of various intrusive phases and the occurrence of the two zircon generations within a single intrusive phase suggest that these phases of magmas are generated from diverse sources during post-collisional continental extension. These magmas ascend rapidly and cool quickly in a short interval.

Sediment recycling and indication of weathering proxies

As a result of recycling, the mineralogical and chemical compositions of riverine sediments may reflect the combined effects of the present-day weathering regime as well as previous weathering and diagenetic alteration history. River sediments can be interpreted as a mixture of non-weathered bedrock—of igneous, metamorphic, or sedimentary origin—and solids formed by the modern weathering system. The correlation between the weathering proxies chemical index of alteration and weathering index of Parker offers an approach to distinguish fine suspended particles, coarse bedload sediments, and recycled sediments under the influence of quartz dilution. Recycling of cation-depleted source rocks formed during past geological weathering episodes may have great impacts on the weathering indices of sediments from the Changjiang(Yangzte) and Zhuoshui Rivers. Special caution is required when using chemical weathering indices to investigate the intensity of chemical weathering registered in fluvial sediments. To minimize the effect of hydrodynamic sorting or sediment recycling, we suggest that the fine sediments(e.g.suspended particles and ﹤2 lm fractions of bedload sediments) in rivers better reflect the average of weatheredcrust in catchments and the terrigenous end-member in marginal seas.

Zircon U-Pb geochronology and geochemistry of Early Cretaceous granodiorite porphyries in Hutouya,western Shandong and their implications for petrogenesis

Zircon LA-ICP-MS U-Pb age and whole-rock geochemistry data are presented for the Hutouya grano-diorite porphyries in Mengyin, western Shandong, to restrict its petrogenesis. The analyzed zircons exhibit os-cillatory growth zoning and core-rim textures in the cathodoluminescence images and have high Th/U ratios （0.04-1.66）,indicating its magmatic origin. The youngest group of magmatic zircon yields weighted mean 206Pb/238U age of 132 ±2 Ma, which represents the forming age of the granodiorite porphyries, i. e., the Early Cretaceous. The oldest group of magmatic zircon 207Pb/206Pb ages ranges from 2 398 Ma to 2 370 Ma, yielding a weighted mean age of 2 389 ±23 Ma,suggesting that the basement of the North China Craton should exist in the research area. Geochemically, the samples are characterized by high Si02（70. 38% and 64. 87% ） , low MgO （0.60% and 1. 53% ） and Mg# values （42. 92 and 50. 42）. Moreover, they show enrichment of light rare earth elements and large ion lithophile elements （e. g. Rb, Ba and K） , depletion of heavy rare earth ele-ments and high field strength elements （e. g. Nb and Ta） , positive anomaly of Pb, and negative anomaly of Ti. These results, together with previously published data, indicate that the Hutouya granodiorite porphyries were derived from partial melting of a delaminated lower continental crust and subsequent interaction with the mantle peridotites. They are consistent with the period of lithospheric thinning beneath the eastern North China Craton and may be formed in an extensional tectonic environment.

Cu and Zn Speciation in an Acid Soil Amended withAlhalline Biosolids

Fractionation of metals in acid sandy loam soil amended withalkaline-stabilised sewage sludge biosolids was conducted in order toassess metal bioavailability and environmental mobility. Soilsolution was extracted by a centrifugation and filtration technique.Meal speciation in the soil solution was determined by a cationexchange resin method. Acetic acid and EDTA extracting solutions wereused for extraction of metals in soil solid surfaces. Metaldistribution in different fractions of soil solid phase wasdetermined using a three-step sequential extraction scheme.

PALAEOZOIC TECTONIC PALAEOGEOGRAPHY OF THE CATHAYSIA IN EASTERN ZHE JIANG AND NORTHERNFUJIAN, CHINA

Based on the data about sedimentary facies and palaeogeography, this paper proves the existence of the Cathaysia (the part in eastern Zhejiang and northern Fujian, the same hereinafter) and makes a survey about its palaeogeography since Sinian Period. It also discusses the evolution of the tectonic environment of this region during Phanerozoic Eon, according to the features such as the composition of sandstones derived from the old land and alkalinity of volcanic rocks and so on. Continuous uplifting was maintained in Cathaysia during Sinian Period and Paleozoic Era, typically with no significant tectono-magmatic activity being observed. Its northwestern margin belongs to the type of passive continental margin during the middle and late phase of Caledonian Cycle. It showed the characteristics of a steady continent in late Paleozoic era, but was turned quickly into an active continental margin after the middle Jurassic period.

Geochemistry and genesis of magmatic PGE-bearing Cu-Ni sulphide deposit in Wadi Bayhan,southeastern Yemen

The Wadi Bayhan mafic-uhramafic intrusions associated with magmatic PGE-bearing Cu-Ni sulphide deposit are located in the south margin of the Arabian-Nubian Shield, SW Yemen. The intrusions consist of du- nite, olivine-pyroxenite, lherzolite, hornblendite, gabbro and gabbronorite. The dunite and lherzolite are the main host rock for the Cu-Ni ores. The new data of the chemical compositions of the rocks have SiO2 （50% - 53.6% ）, AI203 （0-32%） and MgO （4%-28%）, and relatively low TiO2 （0-3.2%） and K2 0 ＋ Na20 （0. 04% - 5.2% ）. The geochemical characteristics indicate that the parental magma is high-magnesium tholeiitic. Sulfur had reached saturation and immiscible sulfides droplets segregated from silicate magmas before their emplacement.

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

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 province.The volcanic rocks can be divided into Longwangshan,Dawangshan,Gushan and Niangniangshan Formations from early to late.All these volcanic rocks are rich in alkali,and show the similar patterns in rare earth element(REE) distribution.However,some differences can be found in the trace elements and REE patterns.The 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.

Geochemistry and tectonic significance of volcanic rocks from Qushenla Formation in Gerze area of northern Tibetan Plateau

By using petrological,isotope chronological,and geochemical methods,the authors studied the volcanic rocks in the studied area,mainly including dacites and trachytes. The results show that they formed during the late Early Cretaceous. Geochemically,the volcanic rocks are relatively enriched in large-ion lithophile elements( Rb,K,and Th) and depleted in high field strength elements( Nb,Ta,and Ti),and rich in light rare earth elements,and depleted in heavy rare earth elements. The fact indicates that the main body of the volcanic rocks in the Qushenla Formation was derived from the partial melting of lower crust. The lithological assemblages are characterized by continental high-K calc-alkaline and shoshonitic series,suggesting that the southward-subducting oceanic slab in southern Bangong Lake had break off and that the Bangong Lake-Nujiang Ocean had closed before 107 Ma. The main dynamic mechanisms for the genesis of this set of intermediate-acidic volcanic rocks were upwelling of the asthenosphere and partial melting of the lower crust caused by slab break-off.

东海内陆架沉积物磁性特征对早期成岩作用的响应

以东海内陆架泥质区F17柱样为对象,在放射性同位素测年、磁性测量、地球化学和粒度分析的基础上,探讨了早期成岩作用对陆架沉积物磁性特征的影响。结果表明,F17柱样磁性特征存在显著的垂向变化,表现为随深度的增加,沉积物磁性减弱、磁性颗粒变粗和不完整反铁磁性矿物比例上升。粒度以及Al,Ti,Fe,Mn的含量,有机碳和总硫的分析表明,沉积物物源相对均一,粒度虽然存在垂向变化,但不是磁性特征垂向变化的主要原因,早期成岩作用是导致上述磁性特征垂向变化的主要因素。早期成岩过程中,亚铁磁性矿物含量随深度下降的现象与其他地区报道的结果类似,但磁性矿物类型和颗粒大小随深度变化的模式,不同地区存在一定差异。基于磁性矿物对早期成岩过程的敏感性,磁性测量方法对认识铁在陆架沉积物中的迁移和转化具有积极作用。