山东金岭杂岩体内尖晶石-刚玉-碱性长石岩——一种极罕见的富铝碱质交代岩的发现

作者在山东金岭杂岩体内发现了一种由尖晶石刚玉碱性长石组成的富铝碱质交代岩。此类岩石以往国内未曾有过报导，实属罕见。根据该岩石产出的地质、岩石及岩石化学等特征，初步探讨了这类富铝碱质交代岩的形成机理。其成因独具特色，明显不同于由粘土矿经变质作用而形成的杂刚玉，可能是岩浆晚期富含碱质组分（Ｎａ２Ｏ＋Ｋ２Ｏ）的伟晶岩流体与杂岩体内中石炭纪的粘土岩。

秦岭东段泥盆系中似碧玉层纹钠长石岩的发现及其意义

在秦岭东段泥盆系中新发现一种似碧玉层纹钠长石岩,发育有与中泥盆统同样良好的韵律层。野外和室内研究表明,岩石具古热泉沉积成因的可靠信息。这类岩石的发现,对研究秦岭泥盆系铅锌成矿海盆中古地热异常及热泉活动引起的局部热水沉积环境具重要意义,也为了解秦岭造山带泥盆纪时期的成因演化积累了新的资料。

元坝东地区须四段长石岩屑砂岩储层预测方法研究

元坝东地区须四段长石岩屑砂岩储层横向非均质性强,导致沉积相带边界刻画困难、储层预测精度低等问题。通过储层精细标定,明确了储集层的测井及地震响应特征;利用波形分类、均方根振幅属性,明确了储层的宏观展布范围;在储层宏观分布范围内分析储层敏感参数,开展声波曲线重构进行拟声波波阻抗反演,对有利储层分布区及厚度进行精细预测。研究区须四段通过运用地震地质综合储层预测技术所得的储层厚度与实钻吻合,证实该技术可有效提高长石岩屑砂岩储层预测的精度。

含水率对细粒长石岩屑砂岩蠕变特征影响试验研究

煤矿采空区储水库建立过程中,由水的运移引发各种水-岩作用,促使水库坝体长期强度发生变化。为了探究含水率对地下水库坝体蠕变特征影响,以西部梅花井煤矿4-2#煤层底板细粒长石岩屑砂岩为研究对象,通过自制无损浸水加湿设备制取含水率为0%,2%,6%和11%的岩样,采用机械分级加载分别对不同含水率岩样进行三轴蠕变试验,并监测岩样蠕变过程中声发射信号。研究发现随着含水率的增加,岩样蠕变各阶段持续时间显著减少,岩样达到稳定状态所需要时间也相应缩短,同时,岩样的极限应变量呈线性增加,岩样的长期强度呈指数降低,不同含水率长期强度的值与单轴抗压强度的比值为0.3~0.5。声发射RA值监测结果表明,随着含水率的提高,岩样内部拉张裂纹数量明显增加。b值监测结果表明含水率的增加改变了岩石内部结构,岩石试件内部裂隙发育期间,声发射事件普遍比较微弱,随着含水率的增加,试件内部小裂隙比较发育。

樟村-郑坊黑色岩系钒矿床中钡冰长石岩的发现——热水沉积成因的证据

樟村-郑坊黑色岩系钒矿床位于江南吉岛弧靠杨子陆块一侧的边缘海盆地中,除泥盆系、志留系外,从上元古界至第四系地层,该区内都有发育.该矿床含矿岩系为下寒武统,矿体赋存在荷塘组的下部,根据当地地质部门的资料,钒主要赋存在以黑色(碳质)粉砂岩为主的黑色岩系中.我们在对这类容矿岩石的研究中,发现其中存在大量的钡冰长石,所谓的粉砂岩,实质是钡冰长石岩,在矿区中以层状或透镜状、条带状出现.

红河油田川口地区长8储层微观特征研究

红河油田位于鄂尔多斯盆地西缘天环拗陷南部,其主力开发层位为三叠系延长组长8油层组。储层岩石类型主要是岩屑长石砂岩,少数样品中为长石岩屑砂岩,粒度主要为细一中粒,以细粒为主。储层平均有效孔隙度为10.3%,平均有效渗透率0.27×10-3μm2,属于低孔特低渗储层。储层毛管压力曲线呈陡斜式分布,基本无平台发育,排驱压力较高,属于细喉型储层。依据物性和压汞曲线形态及参数特征,将储层毛细管压力曲线划分出三种类型,Ⅰ、Ⅱ类为有效储层,而Ⅲ类为无效储层。砂岩共有4种孔隙组合类型,其中以剩余原生粒间孔+次生粒间孔+粒内溶孔+铸模孔组合为主。

西藏甲马多金属矿床容矿岩石的地球化学特征及其成因初步研究

古海底热水流体所产生的喷流岩是一种具有鲜明特色的地质体,在岩石分类中占有重要位置。它们常常构成某些大型或超大型多金属矿床中极为重要的容矿岩石或含矿岩石,且与矿床成因有十分密切联系。西藏甲马多金属矿床由笔者等人研究(1995)确认为属热水喷流型夕卡岩多金属矿床...

新疆西天山莫托萨拉热水沉积型铁锰矿床矿物学与地球化学特征

莫托萨拉铁锰矿床位于西天山阿吾拉勒成矿带东端,研究程度相对薄弱,在矿床成因方面存在热水沉积、沉积-热液改造、胶体化学沉积等争论。本文详细研究了莫托萨拉最上层锰矿及其围岩的矿物组成、结构构造和地球化学特征,并综合前人资料对整个铁锰矿床的成因做了进一步探讨。本研究首次在矿区发现了热液长石岩,其主要由钠长石、钾长石以及少量重晶石、霓石、锌铁黄长石等矿物组成,类似于"白烟型"热水沉积岩。莫托萨拉最上层锰矿主要由锰橄榄石、褐锰矿、红硅锰矿、磁锰铁矿以及少量重晶石、方铁锰矿等矿物组成,发育有典型的热水内碎屑结构,指示其沉积于海底热液喷流口附近。该层锰矿的Al/(Al+Fe+Mn)值很低(0~0.02)、Si/Al值较高(7.9~10.9)、Fe/Ti值很高(428~1353),通过UCC标准化后发现明显富集Zn、Ba、Pb等元素,而Co、Ni、Cu等元素未见富集,以上地球化学特征与现代海底热液成因铁锰沉积物一致。在Fe/Ti-Al/(Al+Fe+Mn)、SiO_(2)-Al_(2)O_(3)、10×(Co+Ni+Cu)-Fe-Mn、100×(Zr+Ce+Y)-15×(Cu+Ni)-(Fe+Mn)/4等判别图中,莫托萨拉的锰矿层和铁矿层样品均落在海底热液沉积区。锰矿层和铁矿层的稀土元素经PAAS标准化后具有明显的Ce负异常、Eu正异常和Y正异常,与现代海底热液成因铁锰沉积物的稀土配分模式非常相似。综合分析本次研究的矿物学、岩石学、地球化学特征以及前人资料,本文认为莫托萨拉铁锰矿床为海相热水沉积成因,成矿与同期海底火山的间歇性活动密切相关,海底热液的化学组分、温度高低和活动强弱都具有明显的脉动性。莫托萨拉矿区铁锰共存但各自独立成矿,且铁锰分离程度较高,这在显生宙沉积型锰矿中独具特色。鉴于前人曾报道莫托萨拉铁矿石中存在菌藻类微生物化石,我们推测,该矿床的铁锰分离过程除了受控于沉积环境的氧化还原条件变化外,微生物的选择性氧化沉淀可能也发挥了重要作用,值得开展深入研究。

松辽盆地三肇凹陷扶余油层成岩作用及其对储层的影响

松辽盆地三肇凹陷挟余油层储集岩由长石岩屑砂岩、少量岩屑长石砂岩和很少量岩屑砂岩组成。岩石粒度以极细砂为主，有细砂和粉砂。具有高的泥岩岩屑含量。孔隙度在1．40％～20．00％之间，平均为11．15％：渗透率在O．01。163mD之间，平均为1．16mD；以低一特低孔、渗为特征。发生在扶余油层的成岩作用主要有压实作用、胶结作用、溶蚀作用、交代作用。压实作用和胶结作用是破坏储层的最主要作用。高的泥岩岩屑含量、高的地温梯度和细粒沉积物是压卖作用产生强烈影响的重要原因。碳酸盐的沉淀是主要的胶结作用。碎屑颗粒的微晶石英和绿泥石包壳阻止了石英加大。储集岩黏土矿物以高的伊利石、较高的绿泥石、较低的伊蒙混层、低的高岭石和几乎没有蒙皂石为特征。长石和中基性火山岩岩屑的溶蚀对储层是最重要的建设作用。成岩作用已进入晚成岩作用阶段的中期。

Potential Role of Feldspathic Sandstone as a Natural Water Retaining Agent in Mu Us Sandy Land,Northwest China

This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.

Diagenesis and reservoir quality of the fourth member sandstones of Shahejie formation in Huimin depression,eastern China

Petrographic analysis combined with various techniques, such as scanning electron microscopy and X-ray diffraction, was used to assess the timing of growth and original mineral cements, the controls on reservoir and reservoir quality of the fourth member sandstones of Shahejie formation (Es4). The Es4 sandstones are mostly arkose and lithic arkose, rarely feldspathic litharenite, with an average mass fraction of quartz 51.6%, feldspar 33.8% and rock fragments 14.6% (Q51.6F33.8R14.6). They have an average framework composition (mass fraction) of quartz 57.10%, K-feldspar 5.76%, sodium-calcium feldspar 13.00%, calcite 5.77%, dolomite 5.63%, siderite 0.95%, pyrite 0.30%, anhydrite 0.04%, and clay mineral 11.46%. The diagenentic minerals typically include kaolinite, illite-smectite (I/S), illite, chlorite, authigenetic quartz and feldspar, and carbonate and pyrite. Es4 sandstone has undergone stages A and B of eodiagenesis, and now, it is experiencing stage A of mesodiagenesis. Reservoir quality is predominantly controlled by the mechanical compaction, for example, 45.65% of the original porosity loss is related to compaction. The original porosity loss related with cementation is only 26.00%. The reservoir quality is improved as a result of dissolution of feldspar, rock fragment and so forth. The porosity evolved from dissolution varies from 3% to 4%.

Buckling analysis of super-long rock-socketed filling piles in soft soil area by element free Galerkin method

In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditional first type, and a newly invented numerical analysis method, i.e. the element-free Galerkin method (EFGM), was introduced to consider the non-concordant deformation and nonlinearity of the pile-soil interface. Then, based on the nonlinear elastic-ideal plastic pile-soil interface model, a nonlinear iterative algorithm was given to analyze the pile-soil interaction, and a program for buckling analysis of piles by the EFGM (PBAP-EFGM) and arc length method was worked out as well. The application results in an engineering example show that, the shape of pile top load-settlement curve obtained by the program agrees well with the measured one, of which the difference may be caused mainly by those uncertain factors such as possible initial defects of pile shaft and the eccentric loading during the test process. However, the calculated critical load is very close with the measured ultimate load of the test pile, and the corresponding relative error is only 5.6%, far better than the calculated values by linear and nonlinear incremental buckling analysis (with a greater relative error of 37.0% and 15.4% respectively), which also verifies the rationality and feasibility of the present method.

Geochemistry and petrology of rift-related mafic sills and arc-related Gabbro–Diorite bodies, Northern Bafq District,Central Iran

Two types of mafic intrusions have been recognized in the north of the Bafq district, Central Iran. A number of olivine-gabbroic to gabbroic sills intruded the Rizu Formation, comprised of alternating carbonate and volcanic rocks. Mineralogical data show that olivine + pyroxene +brown amphibole(kaersutite) + calcic plagioclase +opaque comprise the olivine-gabbroic rocks, and intermediate(or sodic) plagioclase + altered pyroxene and altered amphibole to biotite + opaque minerals the gabbroic rocks.Both rock types have shown within-plate and alkaline characters and have been presumed to be related to rift formation. The mafic-alkaline magma source of the sills is proposed to have been derived from enriched mantle.Regionally, two Gabbro–Diorite intrusions have been identified in the metamorphic complexes. Mineralogical data suggest that the pyroxene + amphibole(hornblende) +plagioclase + biotite + opaque minerals formed the gabbro to diorite intrusions. These rocks have shown characteristics of calc-alkaline and volcanic arc magmatism.

Big difference in ^87Sr/ ^86Sr ratios of basalt and basin water： higher ^87Sr/ ^86Sr ratios in plagioclase

We analyzed the ^(87)Sr/^(86)Sr ratios of basaltic rocks and basin water in Xuyi,China,and found a big difference,which may challenge conventional wisdom on the contribution of basalt weathering in end-member analysis.Results of an in-house weathering experiment suggest that rainwater and dust are not responsible for the difference.By isolating the major minerals in basalt,we found that plagioclase has much higher ^(87)Sr/^(86)Sr ratios than bulk basalt and basin water,which might explain the difference in ^(87)Sr/^(86)Sr ratios of basalt and basin water.We inferthatlow-temperaturehydrothermalalteration increased the ^(87)Sr/^(86)Sr ratios of plagioclase.Future analyses of end-member contribution in a mixed-rock basin should take into account that basin water and plagioclase have higher ^(87)Sr/^(86)Sr ratios than basaltic rocks.

Effects of Trichoderma harzianum YC_(459) and soil types on seed germination and seedling growth in rock slope restoration

We carried out experiments with various concentrations of Trichoderma harzianum YC459 in different soil types(forest soil, mixed soil,merchantable soil, and leaf mold soil) to evaluate its effect on seed germination and seedling establishment of four species(Festuca arundinacea Schreb., Dianthus barbatus var. asiaticus Nakai,Lespedeza cyrtobotrya Miq., and Parthenocissus tricuspidata Planch) for rock slope restoration. We also investigated the use of drilled slanted holes on the rock slopes for seedling establishment. The results showed that T. harzianum concentration had significant effects on seed germination, seedling growth, and seedling survival for all the species with different soil types. Seed germination and survival rates peaked at 5% T. harzianum concentration with leaf mold soil and decreased as T. harzianum concentration increased from 5% to 10%. Seedling survival rates of all four species were generally lowest at 0% T. harzianum concentration in all soil types.The height of F. arundinacea and L. cyrtobotrya peaked at 5% T. harzianum concentration whereas that of D. barbatus and P. tricuspidata peaked at 10%T. harzianum concentration. We concluded that 5% T. harzianum concentration with leaf mold soil is appropriate for seed germination and seedling survival rates of most species, thus enhancing seedling establishment. Practical application of the findings of this study will contribute in the vegetation restoration of steep rocks in mountain environments.

Petrophysical characteristics of shale oil reservoirs in the Yanchang Formation,Ordos Basin

The mediate-low maturity continental shale oil reservoir in the 7th member of the Triassic Yanchang Formation is one of the main zones for shale oil exploration and development in Ordos Basin,China,but the seismic response mechanism of the reservoir remains unclear.Therefore,developing a new method for“sweet spot”seismic prediction combined with rock physics is necessary.To determine the petrophysical characteristics of continental shale in the 7th member of the Yanchang Formation in the study area,a series of tests,such as a systematic acoustic test on shale oil samples in the target segment,X-ray diffraction analyses,analysis of thin optical sections,and scanning electron microscopy,were conducted to summarize the patterns of seismic elastic property changes.Results show that the shale oil samples of the 7th member of the Yanchang Formation are primarily composed of lithic feldspar sandstone with feldspar dissolution and intergranular pores,widespread micron pores,and throats.Such composition indicates a positive correlation between porosity and permeability.The velocities of the samples are affected by their porosity and mineral composition.Velocity increases with the increase of the calcium content and decreases with the increase of the clay content,indicating a negative correlation with the porosity and total organic carbon(TOC)content on the condition of the same rock structure(quartz skeleton or clay skeleton).The elastic properties of the rock are horizontally isotropic(T1 medium),and the velocity is vertically anisotropic.In addition,the directional arrangement of clay controls the anisotropy of rock velocity.TOC is mainly distributed in the primary intergranular pores,and it has no contribution to the anisotropy of rock velocity.The results of this paper can provide a reference for the seismic prediction of continental shale oil reservoirs in the 7th member of the Yanchang Formation.

Geochronology,geochemistry and Hf isotopic study of Early Carboniferous granodiorites in Taerqi region,central Daxing'anling and its tectonic implication

Zircon U-Pb age,whole rock geochemical and zircon Hf isotopic data are presented for Late Paleozoic granodiorites from the Taerqi region,central Daxing'anling to constrain its petrogenesis and tectonic implication.LA-ICP-MS zircon U-Pb age data indicates that the Late Paleozoic granodiorites were emplaced with age of333.4 ± 2.2 Ma(Early Carboniferous).Geochemically,the granodiorite samples have Si O2= 60.54%-71.40%,Na2 O = 4.04%--4.66%,K2 O = 1.65%--4.27% and Mg O = 0.96%--3.53%,belonging to medium-K to high-K calc-alkaline I-type granites.They are slightly enriched in large ion lithophile elements(e.g.Rb,Th,U and K) and light rare earth elements,and depleted in high field strength elements(e.g.Nb,Ta and Ti),with εHf(t) values of 8.0--11.8 and Hf two-stage model ages of 586-829 Ma.All these geochemical features suggest that the primary magma was derived from partial melting of Neoproterozoic to Phanerozoic newly accreted lower crust.According to the geochemical data and regional geological investigations,the Early Carboniferous granodiorites formed in an island arc setting linked to the subduction of the Paleo-Asian Oceanic Plate beneath the Xing'an Terrane.This also implies that the Xing'an and Songliao terranes have not amalgamated before the Early Carboniferous.

Diagenesis characteristics and their influence on porosity and permeability of sandstone from Yingcheng Formation in Jinshan field

In order to understand the diagenesis and its influence on porosity and permeability of sandstones from Yingcheng Formation in Jinshan field,applying thin sections,casting and scanning electron microscope,the authors studied petrography,diagenesis,porosity and permeability of Yingcheng Formation sandstone reservoir. The results show that the reservoir of Yingcheng Formation is mainly composed of lithic arkoses. Sandstones experienced compaction,pressolution,cementation,metasomatism and dissolution. The primary pores of the sandstones are undeveloped; most of pores are the secondary pores,which are mainly intragranular dissolution pores in feldspar and debris. The compaction and cementation reduced the primary pores in sandstones,the porosity and permeability decreased; while the dissolution formed the secondary pores,resulting in the porosity and permeability increase. Due to compaction and cementation,the porosity and permeability are reduced with increasing of depth. There exists an abnormal enlargement of porosity and permeability within a depth range 2310--2450 m. In combination with analysis of petrology,the dissolution of feldspar and debris is most developed in the depth range. Therefore,compaction,cementation and dissolution are the important factors which affect the porosity and permeability of sandstones.

SHRIMP zircon U-Pb dating of a small tonalite intrusion in metamorphic belt of Chinese Altai orogen and its geological implication

Small granitic intrusions occur in the progressive metamorphic belts of the Chinese Ahai orogen. SHRIMP U-Pb analyses were performed on zircons separated from a tonalite intrusion and yielded a concordant age of 409.6±3.7 Ma （ MSWD = 0.93 ）, restricting the emplacement and crystallization of the tonalite intru- sion to the Early Devonian. Combined with the existing geological data of the contemporary large granitic plutons in the Chinese Altai orogen, the tonalite is considered to be formed together with other granitic rocks in a continental arc setting. The tonalite intrusion has consistent foliation with its country rocks, indicating the strain resuiting in the regional deformation should be very strong during or after the early Devonian.

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.