论四川盆地下中三叠统(T1j-T2L)地下水的形成

四川盆地下中三叠统嘉陵江组—雷口坡组(T1j-T2L)地下水分布广泛,资源丰富,类型各异。其展布规律及水文地球化学景观系在漫长的地质发展历史阶段中,经沉积、掺杂、淋滤、火山活动、生物化学及剥蚀淋滤等多种因素综合作用形成。对其形成分布的研究论述,有助于对地下水资源的开发利用。     

论四川盆地海相三叠系气田地层水水动力驱动条件及对水资源分布的控制

四川盆地海相三叠系嘉陵江组—雷口坡组 (T1 j-T2 L)气田地层水按其构造开启程度、埋藏深度及水化学特征的不同 ,可划分出沉积变质水和渗入淋滤水两种基本成因类型 ,分属两种性质迥然不同的水动力系统 ,各自依据地静压力和静水压力由高压区向低压区驱动的水动力条件 ,控制了盆地海相三叠系气田地层水资源及气藏的保存和分布。     

四川省康定市二郎东石膏矿地质特征及成因分析

二郎东石膏矿位于松潘—甘孜造山带→金汤弧型滑脱—推覆带西南端,矿区内出露地层主要为下泥盆统(D_1),中泥盆统(D_2)、下二叠统(P_1)、中三叠统(T_2)及第四系残坡积物(Q~(edl)),石膏矿体赋存于下泥盆统第二段(D_1~2)的白云岩中,矿体总体受二郎东背斜控制的层状-似层状产出,矿床规模已达大型。     

论四川盆地下、中三叠统蒸发岩的生成模式、成盐机理及找钾展望

四川盆地早中三叠统蒸发岩极为发育,时空分布甚广。蒸发岩的生成模式可分为两大类和四个亚类。即Ⅰ,潮间环境的为(1)泻湖盐湖;Ⅱ,潮上环境的为(2)滨海盐湖;(3)近岸盐湖和(4)远岸盐湖。不同生成模式中,其成盐机理虽对成钾皆不够理想,但仍有希望找到钾盐矿的地区和层段。     

四川盆地西部富钾卤水水文地球化学特征及其成因意义探讨

四川盆地西部宫钾卤水以深层卤水形式赋存于地下４０００余ｍ的中三叠统雷口坡组四段（Ｔ２ｌ４）盐系的碳酸盐岩储层中。富钾卤水与海水不同浓缩阶段相比，其中含Ｋ＋含量异常高，构成液态钾矿资源；Ｂｒ－、Ｉ－、Ｂ（３＋）、Ｌｉ＋等稀有组分也远超过综合利用工业品位，为优质化工原料水。富钾卤水为沉积变质和钾盐溶滤的复合成因，具有固夜态找钾的指示意义。本文为四川盆地固液态找钾提供了有价值的线索。     

四川宣达盐盆富钾富矿卤水地球化学特征及资源意义研究

宣达盐盆富钾富矿卤水产于四川盆地东北部黄金口背斜群南段付家山构造近高点,以深层卤水形式赋存于3260m左右的下三叠统嘉陵江组五段和中统雷口坡组一段(T1j5-T2L1)盐系的碳酸盐岩储层中。卤水与海水蒸发系列相比,K+含量异常高,达25 96g L,超过海水钾盐沉积阶段,也超过综合利用和单独开采品位,为国内外罕见的液态钾矿资源。且富含I-,B3+,Li+,Rb+,Sr2+等多种有用组分,品质优异,构成优质化工原料水,为一种综合性富钾富矿液态矿藏,经济价值极高。卤水为沉积变质水和固态钾盐溶滤水的复合成因。开发利用将可为农业提供优质钾肥,缓解我国钾盐资源不足,并可提供多种短缺的化工产品,对固态钾盐找矿具有重要现实意义。     

内蒙古东乌珠穆沁旗贝格其珠浑迪锌多金属矿化区地质特征及找矿方向

二连浩特——东乌旗是我国北部重要的成矿带。矿区位于东乌珠穆沁旗乌里雅斯太镇东部约30km。区域构造位于西伯利亚板块东南部大陆边缘晚古生代陆缘增生带。工作区地层以上石炭统—下二叠统宝力高庙组(CPb1)陆相安山质火山碎屑岩和碎屑岩建造为主,岩浆岩以中三叠世黑云母钾长花岗岩(T2κγβ)为主。区内断裂构造较为发育,主要有北东向、北西向两组断裂构造,其次为一些北北东向、近东西向断裂构造。目前发现矿化体11条,矿体4条,以锌、钼为主要成矿元素。矿体主要为与中酸性岩有关的锌、钼多金属硫化矿(化)体。据矿化蚀变类型及其赋存状态,推测其成因类型应为岩浆期后中—低温热液—裂隙充填型矿床。     

四川盆地中三叠统雷口坡组雷三、雷四段盐岩沉积环境与成因研究

四川盆地雷口坡组大量钻井资料揭示中三叠统雷口坡组主要成盐期分别为雷三2期和雷四2期。岩性组合特征、沉积环境研究表明,在川中的平昌—南充—遂宁一带发育雷三2期浓缩盐膏质蒸发泻湖微相,在川中-川西地区的南部—盐亭—成都—邛崃地区发育雷四2期盐膏湖盆微相。两期盐岩差异主要表现是,雷三2期时,盆地处于频繁的海进、海退过程中,沉积环境变化较快,成盐环境相对开放,盐盆往往多次蒸发浓缩、补给、淡化,海水表现出接近或者达到盐岩沉积浓度,其间往往夹杂石膏和云质团块沉积。雷四2期时,四川盆地处于持续的海退蒸发期,蒸发量远远大于补给量,海水以蒸发浓缩为主,海水表现为超过石盐沉积浓度,沉积石盐中夹杂卤石,局部地区钾含量极高。     

浅谈新疆罗布泊地区第四纪下限

罗布泊地区东部AK1孔地层根据岩石地层单元和古地磁、孢粉、氧化铁、易溶盐、^14C等测定结果，划分为全新统（Q4）、上更新统（Q3）、中更新统（Q2）、下更新统（Q1）和上新统（N2）。在孔深416.90m处，岩石、构造、古地磁、气候、地球化学等标志均非常明显，结合现在新疆第四纪划分方案，我们认为宜将此界线作为罗布泊地区第四系下界。其位于凯纳事件稍下，年龄约305万年。     

河北平原深州地区JZ孔第四纪年代地层划分研究

通过对河北平原深州地区JZ孔光释光测年、古地磁定年与岩性岩相组合特征的综合分析,划分并厘定了其第四纪年代地层序列。研究认为:该孔全新统(0～10.35 m)底界年龄为10.10 ka B.P.(相当于0.01 Ma B.P.);上更新统(10.35～52.68 m)底界年龄为127.70 ka B.P.(相当于0.128 Ma B.P.);中更新统(52.68～112.17 m)底界年龄为0.78 Ma B.P.(即古地磁B/M界线);下更新统(112.17～365.42 m)底界年龄为2.58 Ma B.P.(即古地磁M/G界线)。该划分方案符合区域地层及沉积环境演化总体特征。JZ孔磁性地层记录的Blake负极性亚时应为区域性极性漂移事件,利用古地磁Blake极性亚时划分河北平原上更新统底界应慎重对待,需有绝对年龄的约束。     

Palaeomagnetism and magnetostratigraphy of uppermost Permian strata, southeast New Mexico, USA: correlation of the Permian–Triassic boundary in non-marine environments

Continental red sandstone and siltstone rocks of the Dewey Lake (Quartermaster) Formation at Maroon Cliffs, near Carlsbad, New Mexico, are characterized by two components of magnetization with partially overlapping laboratory unblocking temperature spectra. Both magnetizations display high coercivities (>100 mT), probably residing in haematite. A north-directed magnetization with steep positive inclination unblocks between 100 and 650 °C, isolating a predominantly northwest-directed magnetization, with shallow inclination, of near uniform normal polarity and maximum unblocking temperatures of 680 °C.
We collected samples from 24 palaeomagnetic sites (i.e. individual beds) from a ~60 m thick section of flat-lying strata disconformably overlying carbonate and evaporite rocks of the Rustler Formation. The upper member of the Rustler Formation contains a Late Permian (early Changxingian) marine invertebrate and conodont fauna. Of the sampled sites, four yield only steep magnetizations, interpreted to be recent overprints. Eight sites did not yield well-grouped site means and were excluded from the final calculations. The formation mean (dec = 337.7°, inc = 9.2°; k = 31.6, α ₉₅ = 7.8°, N = 12 sites) defines a palaeomagnetic pole located at 55.2°N, 117.5°E, in good agreement with other Late Permian North American cratonic poles.
Correlation of the short polarity sequence of this section of Dewey Lake strata is unambiguous. Compared with the polarity stratigraphy of marine sections in Asia, and supported by isotopic age determinations on a widespread bentonite bed in Dewey Lake strata in west Texas (approximately 251 Ma) and fossil data for the underlying Rustler Formation, the magnetostratigraphy is consistent with deposition of the Dewey Lake Formation during the latest Changxingian (Late Permian) stage.     

Interpolation of unit vectors

Summary. Time series of unit vectors occur in geophysics as palaeomagnetic poles or poles of relative motion in plate tectonics, and it is often required to trace a smooth curve through the individual points. A simple method is given for interpolating such time series based on cubic splines. The curve obtained is smooth (e.g. possesses continuous curvature) and does not depend on the choice of coordinate axes. An extension with the same desirable properties is given for the case where the given data are inexact.     

The magnitude of the palaeomagnetic field in Iceland between 2 and 6 Myr ago

Summary. Sixty-eight palaeomagnetic field magnitude values have been determined from a sequence of Icelandic lavas, ranging from 2 to 6 Myr in age. The results indicate large and rapid changes in the palaeomagnetic dipole field and provide a mean value of the palaeomagnetic field magnitude in Iceland for this period.     

An investigation of the magnetic variation within two recent lava flows

Samples collected in vertical sections from two recent (1169 AD and 1971 AD) lava flows show significant variations in both the palaeomagnetic vector and the rock magnetic characteristics. The age and the short cooling time of the flows (both are less than 3 m thick) are such that the observed range of palaeomagnetic variation is more than can reasonably be explained by secular variation. The variations in palaeomagnetic and rock magnetic characteristics appear in part to be a response to the relative proportions of two coexisting ferrimagnetic phases, one that displays a primary coarsegrained and Ti-rich composition and a second that has finer-grained, Ti-poor characteristics. The use of AF demagnetization in this study means that the latter phase will have a disproportionate influence on the palaeomagnetic results. It has been suggested elsewhere that in such a magnetic system the Ti-poor phase may represent a CRM formed at some temperature below its final Curie temperature; if so, the results of this study imply that not only does it affect the palaeointensity estimate (which requires a pure TRM) but it appears also to influence the palaeomagnetic direction to an extent that far exceeds the normal secular change that might be expected to occur during delayed acquisition. Such a result has important implications for palaeomagnetic studies that use lavas, both in the selection of a suitable sampling strategy and in the geomagnetic interpretation of palaeomagnetic variation within single flow units.     

Spectral analysis of Pennocarboniferous geomagnetic variation data from glacial rhythmites

Summary. Palaeomagnetic results for a sequence of Permocarboniferous rhythmites presented in the previous paper have been submitted to maximum entropy spectral analysis to test whether these palaeomagnetic data could supply information on geomagnetic variations. There is a good correlation between the thickness of the rhythmites and sunspot spectra, suggesting that these sediments are really seasonal. The palaeomagnetic spectra are compared with those of observatory records. Periods of approximately 24.4, 12.4, 8.6, 6.7 and 5.5 found for palaeomagnetic data have corresponding values in the geomagnetic spectrum. Most of these periods, however, are the same as those found in the thickness data, implying that magnetization can be influenced by the sedimentation process as suggested by other investigators. On the other hand, both geomagnetic and climatic (thickness) variations seem to be related to solar activity. Therefore, at least indirectly, palaeomagnetic data may reflect geomagnetic variations.     

New palaeomagnetic result from Vendian red sediments in Cisbaikalia and the problem of the relationship of Siberia and Laurentia in the Vendian

A palaeomagnetic study of Vendian red sediments from the Lena River section on the western margin of Lake Baikal in the region of Cisbaikalia (54°N, 108°E) has isolated a stable remanence with direction D = 296.3°, I = −27.7° (high-temperature component) and a corresponding pole of 2.7°S, 168.2°E. The primary nature of this remanence is confirmed from a positive fold test, dual polarities and the presence of detrital haematite. This result, together with all late Precambrian–Early Cambrian palaeomagnetic data from Siberia, indicates that Siberia occupied low latitudes during that time. It has been proposed on the basis of palaeomagnetic data that Laurentia occupied high latitudes during the Vendian, so it would appear that there cannot have been any Laurentia–Siberia connection at that time. A review of Vendian to Cambrian Laurentian palaeomagnetic data shows that such an interpretation is ambiguous. An alternative interpretation places Laurentia in low latitudes and confirms the Laurentia–Siberia fit of Hoffman (1991 ) and Pelechaty (1996 ). However, the lack of Late Vendian palaeomagnetic data for Siberia still allows the possibility that it could have occupied high latitudes during that time.     

Palaeomagnetism of the Lower Ordovician Orthoceras Limestone, St. Petersburg, and a revised drift history for Baltica in the early Palaeozoic

Palaeomagnetic investigation of Lower Ordovician limestone in the vicinity of St. Petersburg yields a pole position at latitude 34.7°N, longitude 59.1°E ( dp / dm =5.7°/6.4°). A probable primary remanence origin is supported by the presence of a field reversal. The limestone carries one other remanent magnetization component associated with a Mesozoic remagnetization event.
An apparent polar wander path is compiled for Baltica including the new result, ranging in age from Vendian to Cretaceous. Ages of the published Lower to mid-Palaeozoic palaeomagnetic pole positions are adjusted in accordance with the timescale of Tucker & McKerrow (1995). The new Arenig result is the oldest of a series of Ordovician and Silurian palaeomagnetic pole positions from limestones in the Baltic region. There are no data to constrain apparent polar wander for the Tremadoc, Cambrian and latest Vendian. If the Fen Complex results, previously taken to be Vendian in age ( c . 565 Ma), are reinterpreted as Permian remagnetizations, an Early Ordovician–Cambrian–Vendian cusp in the polar wander path for Baltica is eliminated. The apparent polar wander curve might then traverse directly from poles for Vendian dykes on the Kola peninsula ( c . 580 Ma) towards our new Arenig pole ( c . 480 Ma). The consequence of this change in terms of the motion of Baltica in Cambrian times is to reduce significantly a rotational component of movement.
The new Arenig pole extends knowledge of Ordovician apparent polar wander an increment back in time and confirms the palaeolatitude and orientation of Baltica in some published palaeogeographies. Exclusion of the Fen Complex result places Baltica in mid- to high southerly latitudes at the dawn of the Palaeozoic, consistent with faunal and sedimentological evidence but at variance with some earlier palaeomagnetic reconstructions.     

Magnetostratigraphy of the Northern Tian Shan foreland,Taxi He section,China

The Tian Shan range formed in the late Cenozoic in response to the northward propagation of deformation related to the India–Eurasia continental collision. Precise timing of the Tian Shan uplift is required to understand possible mechanisms of continental lithosphere deformation and interactions between climate, tectonism and erosion. Here, we provide magnetostratigraphic age control on the northern Chinese Tian Shan foreland successions. A thorough rock magnetic analysis identifies haematite‐ and magnetite‐bearing alluvial fan deposits in the upper portion of the sampled strata as more reliable palaeomagnetic recorders than magnetite‐bearing fluvial and lacustrine deposits that are often maghaemitized in the lower part of the record. As a result, a robust correlation to the geomagnetic polarity time scale is obtained from 6 to 2 Ma while a tentative correlation is proposed from 6 to 16 Ma. Sediment accumulation rates increase from 155 to 260 m Myr^?1 at 3.9±0.3 Ma. This change coincides with a gradual lithologic transition from fluvial (sandstone‐dominated) to alluvial fan (conglomerate‐dominated) deposits that likely records an approaching erosional source related to tectonically increased subsidence rather than differential compaction. Clear evidence for growth strata starting at an estimated age of ～2 Ma provides a minimum age for folding. These results are compared with previous magneotstratigraphic studies from the same and other sections of the northern Tian Shan foreland basin fill, thus enabling a critical assessment of the reliability of magnetostratigraphic dating and the significance of sediment accumulation rate variations with respect to facies variations and growth strata. Our results in the Taxi He section provide a sequence of events that is consistent with enhanced tectonic forcing starting at ～4 Ma, although a climatic contribution must be considered given the close relationship of these ages with the Pliocene climate deterioration.     

The British Tertiary igneous province: palaeomagnetism of the dyke swarm along the Sleat coast of Skye

Summary. A palaeomagnetic investigation has been made of a swarm of more than 400 dykes along the south coast of Skye, Scotland, by the Sound of Sleat.
Seven red lamprophyre dykes have palaeomagnetic directions inconsistent with Tertiary age, and not inconsistent with their previously held Caledonian age. The remaining 409 dykes have palaeomagnetic directions that are consistent with a Lower Tertiary age. We present evidence suggesting that the Tertiary dykes might have been emplaced during a short time, over which the geomagnetic polarity occupied as few as three polarity intervals (NRN or RNR).
Certain 'intermediate' directions of magnetization have also been found, and are presented here.     

Palaeomagnetism of alkaline lava flows from El Salto-Almafuerte, Córdoba Province, Argentina

Summary. Stable components of magnetization have been isolated in 15 lava flows (mean K-Ar age 123 ± 4 Myr) from the alkaline sequence outcropping at El Salto-Almafuerte, Province of Cordoba, Argentina. Magnetic and geologic stratigraphy, as well as K-Ar ages indicate that this sequence was probably extruded in the Lower Cretaceous during the first volcanic cycle of the Sierra de los Cóndores Group (Vulcanitas Cerro Colorado Formation).
The palaeomagnetic pole-position for El Salto-Almafuerte lava flows, computed from the mean of 15 virtual geomagnetic poles and denoted SAK₇, is: 25° E, 72° S ( k = 35, α₉₅= 6.5°); it is fairly close to other Lower Cretaceous palaeomagnetic poles for South America. The elongated distribution of Cretaceous palaeomagnetic poles suggest recurrent drift for South America in early Cretaceous time.
The palaeomagnetic and radiometric data for the igneous rocks from El Salto-Almafuerte support the magnetic reversal time-scale for the early Cretaceous suggested by oceanic magnetic lineations.