GPS-derived crustal deformation in southwestern China

The Sichuan – Yunnan region is divided into nine active secondary crustal blocks, based on several GPS repeat surveys at more than 200 GPS sites during the period 1999 – 2005. Velocities of the nine secondary blocks are calculated and analysed. The strain field within the area related to the 2004 Sumatra – Andaman earthquake event is also analysed. Results indicate that the crustal movement in the northern and western areas of the Sichuan – Yunnan region is stronger than that in the south and east. The horizontal velocities change from 19 – 20 mm/y in the northern and the central rhombic block to 11.7 mm/y in the southern rhombic block. The orientations of block motion vary from 99° in the north to 126 – 150° in the central area and 156 – 188° in the south, implying that the motion of the Sichuan – Yunnan rhombic block is dominated by a clockwise rotation. The velocity differences between blocks inside and outside the rhombic block are about 6.5 – 7.7 mm/y in the northern and central Sichuan – Yunnan region. The southeastward extrusion rate of the Tibetan Plateau shows a remarkable downtrend of up to 47% along the Xianshuihe Fault, suggesting an increase in strain accumulation and hence an area prone to strong earthquakes. The horizontal coseismic deformation caused by the Mw9.0 Sumatra – Andaman earthquake is <10 mm with a south-southeast orientation towards the earthquake epicentre. The dilatational strain rates from coseismic displacements reveal a possible interaction between the extrusion from the Tibet plateau interior and the underthrust effects from the Sumatra – Andaman earthquake.     

Zircon U–Pb geochronology and geochemistry of Late Cretaceous–early Eocene granodiorites in the southern Gangdese batholith of Tibet: petrogenesis and implications for geodynamics and Cu ± Au ± Mo mineralization

Cu ± Au ± Mo mineralization is found in multiple intrusive suites in the Gangdese belt of southern Tibet (GBST). However, the petrogenesis of these ore-bearing intrusive rocks remains controversial. Here, we report on mineralization-related Late Cretaceous-early Eocene intrusive rocks in the Chikang–Jirong area, southern Gangdese. Zircon U–Pb analyses indicate that the mainly granodioritic Chikang and Jirong plutons were generated in the Late Cretaceous (ca. 92 Ma) and early Eocene (ca. 53 Ma), respectively. They are high-K calc-alkaline suites with high SiO₂ (64.8–68.3 wt.%) and Al₂O₃ (15.1–15.7 wt.%) contents. Chikang granodiorites are characterized by high Sr (835–957 ppm), Sr/Y (118–140), Mg# (58–60), Cr (21.8–36.6 ppm), and Ni (14.3–22.9 ppm), and low Y (6.0–8.1 ppm), Yb (0.54–0.68 ppm) values with negligible Eu anomalies, which are similar to those of typical slab-derived adakites. The Jirong granodiorites have high SiO₂ (64.8–65.3 wt.%) and Na₂O + K₂O (7.19–7.59 wt.%), and low CaO (2.45–3.69 wt.%) contents, Mg# (47–53) and Sr/Y (14–16) values, along with negative Eu and Ba anomalies. Both Chikang and Jirong granodiorites have similar ε_Hf(t) (7.6–13.1) values. The Chikang granodiorites were most probably produced by partial melting of subducted Neo-Tethyan oceanic crust, and the Jirong granodiorites were possibly generated by partial melting of Gangdese juvenile basaltic crust. In combination with the two peak ages (100–80 and 65–41 Ma) of Gangdese magmatism, we suggest that upwelling asthenosphere, triggered by the rollback and subsequent break-off of subducted Neo-Tethyan oceanic lithosphere, provided the heat for partial melting of subducted slab and arc juvenile crust. Taking into account the contemporaneous occurrence of Gangdese magmatism and Cu ± Au ± Mo mineralization, we conclude that the Late Cretaceous–early Eocene magmatic rocks in the GBST may have a significant potential for Cu ± Au ± Mo mineralization.     

Tertiary stratigraphy of Western Australia

This paper is a summary of the present knowledge of the Tertiary stratigraphy of Western Australia. Also included is new information on the Cainozoic of the Carnarvon Basin, a result of petroleum exploration in the area.

Tertiary rocks formed during more than one cycle of deposition in three basins (Eucla, Perth, and Carnarvon), and also as thin units deposited in a single transgression along the south coast. The Tertiary stratigraphy of the Bonaparte Gulf Basin is not well known.

Drilling in the Eucla Basin has encountered up to 400 m of Tertiary in the south central part, with uniform thinning towards the margins. The section begins with a middle‐upper Eocene carbonate unit which represents the dominant event in the Tertiary sedimentation in this basin. More carbonates were deposited in the late Oligocene‐early Miocene and middle Miocene.

Along the south coast, the so‐called Bremer Basin, the Plantagenet Group (up to 100 m) of siltstone, sandstone, spongolite, and minor limestone, was deposited during the late Eocene.

The Perth Basin contains up to 700 m of Tertiary sediment, formed during at least two phases of sedimentation. The upper Paleocene‐lower Eocene Kings Park Formation consists of marine shale, sandstone, and minor limestone, with a thickness of up to 450 m. The Stark Bay Formation (200 m) includes limestone, dolomite, and chert formed during the early and middle Miocene. Events after deposition of the Stark Bay Formation are not well known.

The northern Carnarvon Basin and Northwest Shelf contain by far the most voluminous Tertiary sediment known from Western Australia: 3500 m is known from BOCAL's Scott Reef No. 1. A more usual maximum thickness is 2500 m. Most sediments were laid down in four episodes, separated by unconformities: late Paleocene‐early Eocene; middle‐late Eocene; late Oligocene‐middle Miocene; and late Miocene to Recent.

The Paleocene‐early Eocene cycle consists of about 100–200 m (up to 450 m in the north) of carbonate, shale, and marl of the Cardabia Group containing rich faunas of planktonic foraminifera.

The middle‐late Eocene sediments include diverse rock types. Marine and nonmarine sandstone formed in the Merlinleigh Trough. At the same time, the Giralia Calcarenite (fauna dominated by the large foraminifer Discocyclina) and unnamed, deeper water shale, marl, and carbonate (with rich planktonic foraminiferal faunas) formed in the ocean outside the embayment. Thickness is usually of the order of 100–200 m.

The main cycle of sedimentation is the late Oligocene‐middle Miocene, during which time the Cape Range Group of carbonates formed. This contains dominantly large foraminiferal faunas, of a wide variety of shallow‐water microfacies, but recent oil exploration farther offshore has recovered outer continental shelf facies with abundant planktonic foraminifera. A minor disconformity representing N7 and perhaps parts of N6 and N8 is now thought to be widespread within the Cape Range Group. The last part of this cycle resulted in sedimentation mainly of coarse calcareous marine sandstone (unnamed), and, in the Cape Range area, of the sandstone and calcareous conglomerate of the Pilgramunna Formation. Maximum thickness encountered in WAPET wells is 900 m.

After an unconformity representing almost all the late Miocene, sedimentation began again, forming an upper Miocene‐Recent carbonate unit which includes some excellent planktonic faunas. Thickness is up to 1100 m.

Thin marine sediments of the White Mountain Formation outcrop in the Bonaparte Gulf Basin. They contain some foraminifera and a Miocene age has been suggested.     

Atypical stratiform sulfide-poor platinum-group element mineralisation in the Agnew – Wiluna Belt komatiites,Wiluna, Western Australia

A new style of komatiite-associated sulfide-poor platinum-group element (PGE: Os, Ir, Ru, Rh, Pt, Pd) mineralisation has been identified at Wiluna in the strongly nickel sulfide (NiS) mineralised Agnew – Wiluna Greenstone Belt, Western Australia. The komatiite sequence at Wiluna is ～200 m thick and comprises a basal pyroxenite layer, a thick ortho-to-mesocumulate-textured peridotite core, which is overlain by rhythmically layered wehrlite, oikocrystic pyroxenite and thick upper gabbroic margins. Pegmatoid and dendritic (harrisitic) domains are common features, whereas spinifex-textured horizons and flow-top breccias are absent. The presence of anomalous PGE-enriched horizons (ΣPt – Pd = 200 – 500 ppb) in the oikocrystic pyroxenite and in the layered melagabbro and gabbronorite horizons directly overlying the wehrlite unit is due to the presence of fine-grained (1 – 10 μm) platinum-group minerals (PGMs). More than 70 PGM grains were identified, and a considerable mineralogical variability was constrained. However, only Pd – Pt-bearing phases were identified, whereas no Ir – Ru-bearing PGMs were found in any of the sections examined. Interestingly, all PGMs are not in paragenetic association with sulfides, and only sulfide-poor/free intervals contain significant PGM concentrations. The whole-rock PGE sequence largely reflects the PGM distribution. It is hypothesised that the Pd – Pt enrichment in the oikocrystic pyroxenite and melagabbros and the overall Ir – Ru depletion in the upper mafic section of the sequence are the result of extensive olivine and chromite crystallisation in the basal ultramafic section. PGE saturation was driven by extensive crystallisation of silicate and oxide phases in a sulfide-undersaturated environment. The crystallisation of clinopyroxene in the oikocrystic pyroxenite horizon may have triggered the formation of Pt – Pd-bearing alloys and arsenides, which were the first PGMs to form. Stratiform sulfide-poor PGE mineralisation at Wiluna is more similar in stratigraphic setting, style and composition to PGE-rich sulfide-poor mineralisation zones in thick differentiated intrusions, rather than to other PGE-enriched zones in komatiite-hosted systems, where PGE enrichment is directly associated with accumulations of magmatic sulfides.     

Structural history of the Greenvale Province,north Queensland: Early Palaeozoic extension and convergence on the Pacific margin of Gondwana*

The southeastern Georgetown Inlier (Greenvale Province) consists of Early Palaeozoic metamorphic rocks in fault contact along the Lynd Mylonite Zone with the Palaeoproterozoic to Mesoproterozoic craton of northeastern Australia. It has a central assemblage of metamorphosed silicic volcanic and sedimentary rocks considered equivalent to the Late Cambrian to Early Ordovician Seventy Mile Range Group that developed in an extensional backarc in the Charters Towers Province to the southeast. In the western part of the Greenvale Province, the Oasis Metamorphics have a U – Pb zircon SHRIMP metamorphic age of 476 ± 5 Ma and are intruded by the granodioritic Lynwater Complex with U – Pb zircon ages of 486 ± 5 Ma and 477 ± 6 Ma. These ages are consistent with these rocks forming basement and intrusive equivalents to the extensional volcanic basin. Existing geochronological constraints on the Halls Reward domain, located at the eastern margin of the province, are consistent with it being basement to the extensional basin. Several domains are recognised in the Greenvale Province with either dominantly steep or low to moderate dips of the main foliation, and each experienced multiple deformation with locally up to four overprinting structural phases. Steepening of foliation in several of the domains is attributed to contractional deformation in the Early Silurian that is inferred to have overprinted low-angle foliation developed during extensional tectonics in the backarc setting. Contractional deformation related to the Early Silurian Benambran Orogeny is considered responsible for multiple deformation in the Greenvale Province and reactivation of domain-bounding faults.     

A cave in Dolerite at Wayatinah,Tasmania

A cave (60 ft. x 30 ft. x 17 ft.) occurs within Jurassic dolerite 600 ft. from the surface. It was formed by zeolitization of a zone in the dolerite followed by solution of the secondary minerals to leave a cavity.     

Evaluating the provenance of Archean sedimentary rocks of the Diemals Formation (central Yilgarn Craton) using whole-rock chemistry and precise U – Pb zircon chronology

Whole-rock chemistry and precise U – Pb zircon chronology have been used to determine the provenance of Archean greenschist-facies siliciclastic sedimentary rocks of the Diemals Formation in the Marda – Diemals area of the central Yilgarn Craton, Western Australia. Field evidence shows that these siliciclastic rocks are, at least in part, derived from uplift and erosion of underlying greenstones, and this is borne out by the similar La/Sc, Cr/Th and REE chemistry of Diemals Formation siltstones and some sandstones to mafic volcanic rocks of the underlying greenstones. The higher Cr/V and lower Y/Ni of some siltstones is consistent with input from ultramafic and mafic rocks. Diemals Formation sandstones and siltstones cannot be separated in terms of ratios such as Zr/La, and siliciclastic rock chemistry reflects provenance rather than the effects of transport and depositional processes, such as sorting. Chemistry does not support input to Diemals Formation sedimentary rocks from the Marda volcanic complex despite both units being close to each other, and having overlapping maximum depositional and crystallisation ages, respectively. Instead, it is likely that detritus for the two units was deposited in adjacent, physically discrete basins. Some Diemals Formation sandstones are geochemically similar to felsic rocks intruding the underlying greenstone succession, with higher La/Sc and lower Cr/Th, and LREE-enriched patterns with negative Eu anomalies. Support for a genetic relationship is shown by the overlap in the maximum depositional age of these sandstones with the crystallisation age of the geochemically identical Pigeon Rocks Monzogranite. Combined whole-rock chemistry and precise U – Pb zircon chronology indicates that Diemals Formation sedimentary rocks were in large part derived from the underlying mafic volcanic rocks, with progressive unroofing of this succession leading to erosion of felsic intrusive rocks, now represented by sandstones found at various levels in the Diemals Formation.     

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

The effects of failure mode transition from tensile to shear on structural style and fault zone architecture have long been recognized but are not well studied in 3D, although the two modes are both common in the upper crust of Earth and terrestrial planets, and are associated with large differences in transport properties. We present a simple method to study this in physical scale models of normal faults, using a cohesive powder embedded in cohesionless sand. By varying the overburden thickness, the failure mode changes from tensile to hybrid and finally to shear. Hardening and excavating the cohesive layer allows post mortem investigation of 3D structures at high resolution. We recognize two end member structural domains that differ strongly in their attributes. In the tensile domain faults are strongly dilatant with steep open fissures and sharp changes in strike at segment boundaries and branch points. In the shear domain fault dips are shallower and fault planes develop striations; map-view fault traces undulate with smaller changes in strike at branches. These attributes may be recognized in subsurface fault maps and could provide a way to better predict fault zone structure in the subsurface.     

Lake Boga Granite,northwestern Victoria: mineralogy,geochemistry and geochronology

The Devonian Lake Boga Granite in northern Victoria, while almost entirely under thin Murray Basin cover, is one of the largest plutons in the western Lachlan Fold Belt. Its only exposure is a quarry penetrating the Cenozoic sediments. In the quarry, prominent pod pegmatites and miarolitic cavities suggest a high level of emplacement. The granite, a non-magnetic, fractionated S-type, contains a large range of accessory minerals, including primary uranium- and REE-bearing phosphates and oxides, and primary copper sulfides. Monazite-series minerals show an exceptionally wide range of compositions, from normal monazite-(Ce) through cheralite (Ca – Th-rich) to rare huttonitic monazite (Th-rich) and brabantite; U contents in monazite also vary widely (0 – 7.9 wt%). Primary low-Ca uraninites are well preserved and are unusual in having low Th/U and LREE. Late-stage cavity fluorapatite crystals up to several centimetres across show intricate elemental zoning patterns with extreme U gradients (<10 – 6900 ppm) in some crystals. New ⁴⁰Ar – ³⁹Ar ages for magmatic biotite, muscovite and K-rich feldspar average 365 ± 3 Ma, which approximates the emplacement age of the granite. This is supported by a 377 ± 12 Ma U – Th – Pb (CHIME) age for primary uraninite. New whole-rock geochemical data support earlier observations: the granite is strongly fractionated (SiO₂ 70.7 – 76.0 wt%; 4.2 – 0.6 wt% FeO_t) and peraluminous (ASI = 1.23 – 1.45), and has slightly elevated Na₂O and P₂O₅ (0.30 wt%) contents compared with other fractionated S-type granites from the Lachlan Fold Belt. Trace-element abundances are typical of fractionated granites, although U and Cu concentrations vary strongly and reach >60 and ≈1400 ppm, respectively. REE patterns also vary strongly, from LREE-enriched with moderate Eu depletion, to flat with strong Eu depletion. The flattest of the REE patterns, in samples with FeO_total < 1%, are characterised by M-type tetrad effects. These and other samples also show low (subcrustal average) and variable Zr/Hf (35 – 16) and Nb/Ta (8 – 4) ratios; these and other unusual elemental fractionations are related to changes in elemental partitioning during the late magmatic stage, when felsic peraluminous magma and high-temperature magmatic fluid coexisted.     

Thermal history of a Late Mesoproterozoic paired metamorphic belt (?) during Rodinia assembly: New insight from medium-pressure granulites from the Aravalli-Delhi Mobile Belt,Northwestern India

In this study, we investigate the possible record of a Late Mesoproterozoic paired metamorphic belt in the Aravalli-Delhi Mobile Belt(ADMB), NW India using a suite of supracrustal and metaigneous granulites from the Pilwa-Chinwali granulite terrain at the north-western margin of the ADMB. Using metamorphic reaction textures, mineral chemistry, metamorphic reaction history, geothermobarometric computations and electron microprobe dating of monazite in 5 samples of pelitic granulite, leptynite gneiss, enderbite and charnockite, we have deduced a medium-pressure granulite facies metamorphism(P between 4.9 and 6.8 kbar, T 760-815℃) along a heating-cooling, counterclockwise P-T path between 1.09 and 1.01 Ga. When collated with published metamorphic and chronological constraints and geological settings of the adjoining crustal domains of the ADMB, these findings provide new insights into the developments of two tectonic domains of contrasting thermal gradients at ca. 1.0 Ga, consistent with metamorphic transformations in tectonically thickened middle-lower crustal sections during continental collision to continental subduction and in the root zones of spatially adjacent island arc, as part of the Rodinia supercontinent assembly event.     

东秦岭160～140Ma Cu(Mo)和Mo(W)成矿作用的差异性:来自成矿岩体的地球化学及其岩浆源区的证据

东秦岭地区在商丹断裂带南北两侧分别形成了矽卡岩-斑岩型Cu(Mo)矿床和斑岩-矽卡岩型Mo(W)矿床,两者均形成于160~140Ma。通过对不同矿床的地质特征和成矿岩体对比研究发现,Mo(W)矿床主要分布在商丹断裂带北侧的北秦岭和华北板块南缘,主要分布有新太古代至奥陶纪地层,由一系列变质程度不同的火山岩和沉积岩组成。Cu(Mo)矿床主要位于商丹断裂带南侧的南秦岭晚古生代弧前盆地,主要分布古生代地层,由粉砂岩、绢云板岩、灰岩、杂砂岩及白云岩等组成。Mo(W)矿床的成矿岩体以花岗斑岩为主,具有高硅、富钾,贫镁铁,较高的岩浆分异程度;Cu(Mo)矿床的成矿岩体以花岗闪长斑岩为主,具有低硅、低钾,富镁铁,低分异的特征。Mo(W)成矿岩体亏损Ba,富集U、Nb等元素,Cu(Mo)成矿岩体相对富集Ba,亏损U、Nb等元素;Cu(Mo)成矿岩体∑REE略高于Mo(W)成矿岩体,未表现出明显的Eu异常,而Mo(W)成矿岩体具有负Eu异常。Cu(Mo)和Mo(W)成矿岩体具有相似的结晶温度,Mo(W)成矿岩体具有相对较高的形成压力和氧化态。Mo(W)成矿岩体的岩浆源区以辉石为残留相,Cu(Mo)成矿岩体的岩浆源区则是以极少量角闪石为残留相。相对于Mo(W)矿床,Cu(Mo)矿床的成矿岩体具有较高的εNd(t)值(-28.8~-12.1和-4.75~-2.73)和εHf(t)值(-38~-7.9和-3.79~+1.79),这说明Cu(Mo)成矿岩体的岩浆源区中含有相对较多的地幔物质,而Mo(W)成矿岩体的岩浆源区中含有相对较多地壳物质。由于两种矿化位于不同的构造单元以及成矿岩体在岩石地球化学、温压条件、氧化还原状态和岩浆源区特征等方面的差异造成了160~140Ma岩浆活动在商丹断裂带南北两侧形成不同矿化类型。     

Major and trace element geochemistry of olivine from an ENE-trending picrite dyke,genetically linked to the ca. 1.89–1.88 Ga Hampi swarm,western Dharwar craton: Implications for plume induced melting of a mixed peridotite-pyroxenite source

The presence of recycled crust in the lithospheric mantle of the Dharwar craton has been investigated using trace element geochemistry of olivine grains from an ENE-trending Paleoproterozoic picrite dyke (associated with the ca. 1.89–1.88 Ga Hampi dyke swarm) emplaced in the western Dharwar craton. Olivine grains are purely magmatic, formed as early phenocrysts in a fractionated basaltic melt. They exhibit enrichment in NiO contents (0.32–0.43 wt%) and depletion in Ca (1366–2105 ppm), Mn (1578–2663 ppm) and 100 1 Mn/Fe (1.28–1.48). Further, the compiled whole-rock geochemical data of the picrite dyke and associated dyke swarm illustrates relatively low CaO/MgO (0.55–1.78), intermediate FeO/MnO (47–54), negative to positive PX# (?0.34 to +1.86), and high values of FC3MS (0.24–0.90) and FCKANTMS (0.19–1.11). These chemical markers are not consistent with the derivation of the primary melt from a pure peridotite or a pyroxenite source; therefore, contribution from a mixed type of source having both peridotite and pyroxenite end members (pyroxene rich and olivine poor lithology) is suggested. The amount of pyroxenite and recycled crust varies from 46% to 86% and 14% to 44%, respectively. The Al-in-olivine based thermometer estimates the maximum crystallization temperature as 1407 °C, which is 137 °C higher than the average temperature of MORB and accordant with several well-established plume-induced large igneous provinces (LIPs) worldwide. Therefore, it is suggested that the studied picrite dyke is derived from a primary melt generated by plume-induced melting of a peridotite-pyroxenite mixed source. The ca. 1.89–1.88 Ga Hampi dyke swarm, being genetically linked with the studied dyke, could also be derived from this same source. Further, the recycled crust in the subcontinental lithospheric mantle of the western Dharwar craton may have generated the pyroxene rich mafic source during the Neoarchean convergence between eastern and western Dharwar craton.     

深基坑边坡支护方式的现状

根据目前国内边坡支护工作中的主要方式,将深基坑边坡支护按其结构的受力状态和支护的作用原理进行分类,详细论述了各种深基坑边坡支护方式的机制和适用条件,对今后岩土工程的实际工作具有一定的参考作用。     

鄂尔多斯盆地延长组长7富铀烃源岩铀的赋存状态

鄂尔多斯盆地晚三叠世延长组长7段是一套深湖相富铀烃源岩,铀含量很高,其矿物学特点是富含胶磷矿、草莓状黄铁矿、有机质等.通过光片、扫描电镜、电子探针、能谱分析、α放射性照相等研究方法,分析了长7段富铀烃源岩中铀的赋存状态,结果表明铀除了以类质同象赋存于胶磷矿中,以及以吸附态赋存于黄铁矿和有机质中以外,还在长7富铀烃源岩中...     

沉管隧道基槽爆破施工对既有堤岸稳定性影响的数值仿真分析

结合爆破数值模拟中爆破荷载的特点,分析了各种荷载施加方法的特点及爆破震动场模拟的要求,基于圣维南荷载等效原理,提出了爆破荷载的等效施加方法,即将作用在炮孔壁上的爆破荷载等效后,施加在同排炮孔中心线或者面上来模拟爆破荷载的作用。结果表明,等效施加方法在近区存在一定差异,但在中远区吻合得较好。利用该等效荷载施加方法,采用三维实体模型计算分析了某沉管隧道基槽爆破施工对既有堤岸稳定性影响,计算了周围不同位置、不同深度位置处的振动响应,并在此基础上,分析研究了减小爆破振动对既有结构物影响的减振措施,可为类似工程提供借鉴。     

铜精矿化学成分分析实验室间比对结果评价和离群值原因分析

铜精矿成分分析是判定其品质的重要手段,尤其是主元素铜的分析.目前,测定铜精矿中铜含量的主要分析方法有碘量法、电感耦合等离子体发射光谱法(ICP-OES)、火焰原子吸收光谱法(FAAS)、X射线荧光光谱法(XRF)、电解重量法等.为确保检测标准量值统一、准确、可靠,本文组织开展了铜精矿中铜镁铅锌的测定实验室间比对活动.通...     

焦家式金矿中铬铝云母化学成分的标型性

本文系统研究了胶东地区金矿中产出的铬铝云母亚族中３个白云母、１６个绢云母和３２个含Ｃｒ云母种属的化学成分特征。提出了含Ｃｒ云母种属结构层内四面体、八面体及层间离子种类和数量在焦家式金矿成矿过程中的指示作用，阐明了白云母、绢云母及含Ｃｒ云母种属之间的演化特征在与焦家式金矿化有关的成岩成矿作用中的标型意义。     

Structure of sediments of kaolinite

In an assembly of clay particles placed in a fluid, each particle is typically subjected to: (1) double-layer repulsive forces; (2) van der Waals attractive forces; and (3) contact mechanical forces. The study presented here concerns an approximate, quantitative analysis of clay suspensions, with considerations to the first two - the physico-chemical forces. Using recent theories to calculate the physico-chemical forces between two clay particles in an approximate model of an assembly, the equilibrium void ratio of a clay suspension is computed. The mechanical forces are ignored in the analysis. The results serve to verify the validity of physico-chemical theories employed and help interpret experimental data more fundamentally in terms of the system variables.     

山西高凡金矿的找矿矿物学研究

高凡金矿床是次火山热液型中低温金（银）矿床，对矿石中主要矿石矿物自然金、石英，黄铁矿，银矿物，闪锌矿，方铅矿和方解石等矿物标型性研究，得出了高凡金（银）矿床的矿物标型特征及空间分布规律，利用这些规律可指导该矿床深部的找矿工作及区域上同类型矿床的寻找。     

济阳坳陷车镇凹陷古近系沙河街组遗迹化石Macaronichnus(通心粉管迹)及其沉积环境

济阳坳陷车镇凹陷古近系沙河街组发现的Macaronichnus segregatis(分离通心粉管迹)是一种直到微弯曲形状的层内进食潜穴,个体较小,不分枝,长一般7～8 mm,直径1～3 mm,与前人发现的化石在个体大小上存在着差异。它主要出现于四类环境：①三角洲平原河道间低地,②三角洲、扇三角洲前缘远端砂坝和浊积扇的中扇到外扇,③潮湿气候条件下的浅湖,④周期性干旱气候条件下的滨浅湖。不同沉积环境中产出的Msegregatis都分布于粉砂质泥岩中。通过分析各沉积环境的水动力条件和水体化学性质以及Msegregatis的形成过程,可得出以下结论：①Msegregatis出现的水动力条件中等,水体能量过高或过低,都不适宜其生成;②Msegregatis出现的水体化学性质介于贫氧与富氧之间;③Msegregatis是在沉积物沉积后还未固结时由食沉积物生物活动造成的,衬壁的出现反映了软基底性质。