Chemistry, small-scale inhomogeneity, and formation of moldavites as condensates from sands vaporized by the Ries impact

The formation of the Ries impact and the moldavites have identical radiogenic ages of 14.3 Ma. According to this conformity in age moldavites are generally regarded as products of the Ries impact. This paper, which is divided into two sections, deals with two aspects of the moldavite-forming process: the formation of moldavite bodies by accretion of small precursors, and the physical and chemical conditions under which these primary units originated from sands which covered the Ries impact site.First, the chemical inhomogeneity of moldavite glasses is investigated in sections of 11 moldavites, using back scattered electron (BSE) images and electron microprobe analyses on 0.4-2.7 mm long traverses. Schlieren and lechatelierite particles are interpreted as relics of small, chemically different precursors, which accumulated to larger moldavite bodies at temperatures too low to be efficient for mixing. The patterns of schlieren and lechatelierite inclusions represent two successive rheological regimes: Small agglomerating primary melt units were extended into thin lamellae and threads under conditions of laminar flow. As evidenced by folded textures, these fluidal arrays were later plastically deformed under conditions of compressional stress.To elucidate the production of the primary melt units by the Ries impact, in the second section the geologic situation of the Ries area is considered with regard to possible source materials. The site of the Ries impact, situated at the northern border of the pre-Alpine Molasse basin, was covered at the time of the impact by fluviatile sediments of the lower sequence of the Obere Süßwasser-Molasse (OSM) Formation of Middle Miocene age, consisting of sands, marly sands and clays. Chemical analyses for major and trace elements of 38 moldavites from Bohemia and Moravia, and of 28 samples of the OSM Formation, collected from outcrops and drill holes, immediately south of the Ries crater and south of the Danube, show chemical conformity of moldavites and sand samples with regard to the major parameters SiO_2,Al₂O₃+ FeO, and MgO + CaO, indicating that these sands were the essential source material of moldavites. But, differences in contents of individual major and trace elements between moldavites and sands show that the formation of moldavites from sands involved a specific chemical differentiation which can not be explained by selective vaporization or melting, nor by selective condensation from melt or vapeur. Because large ions were enriched and small ones depleted in moldavites, the ionic radius has controlled the distribution of elements between sands and moldavites. We assume that moldavites originated from a plasma that the impact produced at its encounter with the surficial sand formation at the impact site, and that the primary units formed as early condensates in which large ions were preferentially trapped.     

Moldavites from the Cheb Basin, Czech Republic

Between 1993 and 2007, an estimated 2500-3000 individual moldavite pieces have been found in the Tertiary Cheb Basin, Western Bohemia. This identifies the area as the third most prominent source of Central European tektites, next to the South Bohemian and West Moravian strewn subfields. Basic macroscopic physical properties (weight, shape, color and sculpture) were evaluated for over 350 individual finds of tektites from 4 different localities in the Cheb Basin. All these properties are similar to those observed for the South Bohemian moldavites, particularly with respect of color and weight distribution. In total, 24 tektites from the Cheb Basin have been characterized chemically using electron microprobe. For comparison, a set of 17 moldavites from the South-Bohemian and Moravian strewn subfields was measured as well. Contents of major elements overlap between the two sample sets; the largest variation was observed for iron. The trends observed in the Harker plots, however, seem to differentiate several partial subgroups, some of them characteristic for Cheb tektites only. These results are also substantiated by cluster analysis, which reveals a tight group for most of the tektites from the Cheb Basin, forming two partial clusters. The rest of the Cheb moldavites cluster with the South Bohemian samples. Minor and trace elements were measured with an LA-ICP-MS technique; CI-normalized REE patterns compare well with those for other moldavites. Many tektites, both from Cheb and South Bohemia or Moravia, display considerable heterogeneity: they frequently show schlieren and fluidal fabric. Two samples of this kind from the Cheb Basin showed considerable enrichment in volatile elements (e.g., Zn and Cu), which is typical for Muong Nong-type Australasian tektites. Mössbauer spectroscopy confirmed the highly reducing character of 5 studied moldavites. Discovery of a new moldavite strewn subfield around Cheb substantiates the theory that moldavites were ejected from the Ries impact structure in a fan-shaped jet, although it is not clear yet if it was continuous or composed of individual rays. In addition, the chemistry of the Cheb moldavites indicates significant precursor material heterogeneity.     

川南兴文地区上二叠统龙潭组黏土岩锂的富集特征及赋存状态

四川南部位于二叠纪峨眉山大火山岩省中—外带,广泛分布与火成岩风化- 沉积有关的上二叠统龙潭组黏土岩,具有形成锂等关键金属矿产资源的地质背景和成矿条件。本文对川南兴文地区上二叠统龙潭组下部黏土岩进行了较为系统的地质调查,对研究区以及钻孔岩芯样品进行了化学分析,以确定黏土岩中锂等元素的分布特征及富集规律。在此基础上,利用粉晶X- 射线衍射(XRD)分析了富锂黏土岩的矿物组成,采用聚焦离子束飞行时间二次离子质谱仪(FIB- TOF- SIMS)分析了富锂黏土岩微米尺度上的元素分布特征。结果表明,龙潭组下部黏土岩中富集Li以及Ga、Nb等元素,是一个多种关键金属的富集层,具有良好的成矿潜力和找矿前景。本区黏土岩来源于峨眉山大火山岩省火山岩的风化产物,富锂的矿层主要为含黄铁矿高岭石黏土岩,其沉积成岩环境为海陆过渡地区的潟湖还原咸水环境,Li含量与化学风化强度(CIA指数)密切相关,具有风化- 沉积型矿床的特征。富锂黏土岩中锂除少量赋存于锂云母之中外,主要是被吸附于黏土岩的蒙脱石相中,部分进入蒙脱石矿物结构,还有一部分赋存于伊利石中。Li除了来自火山岩的风化释放以外,部分还可能来自滨海浅层地下卤水的直接补给,从而形成含锂云母的高品位的富锂黏土岩。     

Lithium in tektites and impact glasses: Implications for sources, histories and large impacts

Lithium (Li) abundances and isotope compositions were determined in a representative suite of tektites (moldavites, Muong Nong-type tektites and an australite, Ivory Coast tektites and bediasites), impact-related glasses (Libyan Desert Glass, zhamanshinites and irghizites), a glass fragment embedded in the suevite from the Ries impact crater and sedimentary materials in order to test a possible susceptibility of Li to fractionation during hypervelocity impact events and to de-convolve links to their potential parental sources. The overall data show a large spread in Li abundance (4.7-58 ppm Li) and δ⁷Li values (−3.2‰ to 26.0‰) but individual groups of tektites and impact glasses have distinctive Li compositions.Most importantly, any significant high-temperature Li isotope fractionation can be excluded by comparing sedimentary lithologies from central Europe with moldavites. Instead, we suggest that Li isotope compositions in tektites and impact-related glasses are probably diagnostic of the precursor materials and their pre-impact geological histories. The Muong Nong-type tektites and australite specimen are identical in terms of Li concentrations and δ⁷Li and we tentatively endorse their common origin in a single impact event. Evidence for low-temperature Rayleigh fractionation, which must have operated prior to impact-induced melting and solidification, is provided for a subset of Muong Nong-type tektites. Although Li isotope variations in most tektites are broadly similar to those of the upper continental crust, Libyan Desert Glass carries high δ⁷Li ?24.7‰, which appears to mirror the previous fluvial history of parental material that was perhaps deposited in lacustrine environment or coastal seawater. Lithium isotopes in impact-related glasses from the Zhamanshin crater define a group distinct from all other samples and point to melting of chemically less evolved mafic lithologies, which is also consistent with their major and trace element patterns.Extreme shock pressures and the related extreme post-shock temperatures alone appear not to have any effect on the Li isotope systematics; therefore, useful information on parental lithologies and magmatic processes may be retrieved from analyses of Martian and lunar meteorites. Moreover, lack of significant Li depletion in tektites provides further constraints on the loss of moderately volatile elements during the Moon-forming impact.     

滇东黔西晚二叠世煤系中火山灰蚀变粘土岩的元素地球化学特征

对滇东?黔西晚二叠世煤系中同沉积火山灰蚀变粘土岩夹矸?正常沉积粘土岩和煤层共采46件样品,用多种仪器分析方法测定微量元素30余种?研究表明,煤系各层段中赋存的夹矸是由性质不同的火山灰沉积蚀变形成的,各层夹矸的微量元素含量及组合关系各有特点并在较大范围内保持良好的稳定性,可用于判定层位;正常沉积粘土岩与夹矸的原始物质性质不同,其微量元素含量和组合面貌各有自己特定的分布范围,两者易于区别?     

江汉油田原油和生油岩有机抽提物中过渡族微量元素特征及其石油地球化学意义

运用中子活化分析方法对江汉油田原油和生油岩有机抽提物中过渡族微量元素Sc、V、CrMn、Fe、Co、Ni、Zn等进行了重点研究,测定了这些元素的丰度值。研究了这些元素在原油和有机抽提物族组份:沥表质、非烃和芳香烃中的变化规律。在此基础上,讨论了这些微量元素的相关性,并运用它们的丰度比值对数分布和归一化对数分布,进行了油-源对比的尝试。     

Trace element geochemistry of altered volcanic ash layers (tonsteins) in Late Permian coal-bearing formations of eastern Yunnan and western Guizhou Provinces, China

Trace element compositions were determined (by instrumental neutron activation analysis; INAA) in 30 samples of synsedimentary volcanic ash-derived tonsteins and detrital claystones from coal seams within the late Permian coal-bearing formation of eastern Yunnan and western Guizhou Provinces, China. The characteristics of trace-element geochemistry in the tonsteins can be distinguished from those of detrital claystones because of the former's unique volcanic-ash origin. The detrital claystones are characterized by their relatively high content of V, Ti, Sc, Cr, Co and Ni, relatively low content of Th and U, Th/U ratio, and small negative Eu anomaly (Eu/Eu* 0.63–0.93). Overall, these trace element characteristics are consistent with a mafic source similar to the composition of basalt rocks in the erosional region on the western edge of the study area. In contrast, the tonsteins are low in V, Ti, Sc, Cr, Co and Ni contents and have a high Th/U ratio with a distinct negative Eu anomaly (Eu/Eu* normally in the range of 0.2–0.4), consistent with a silicic magmatic source.Within the group of tonsteins, those from the lower section (P_2.1) of the coal-bearing formation are relatively high in Ti, Zr, Hf, Nb, Ta and rare earth elements (REE), as compared to those from the middle and upper sections (P_2.2+3). In trace-element discrimination diagrams (scatter plots) of Hf–Ta, Ti–Ta, Ti–V, Hf–Sc, Lu–Hf and Lu–Th, tonsteins from the P_2.1 horizon always fall in isolated distribution areas, separate from the tonsteins of the P_2.2+3 horizon. These results suggest that the source materials of tonsteins from the two separate horizons were probably derived from volcanic ash falls of two distinctly different natures. Based on a comparison of the concentrations and assemblages of trace elements between various magmatic rocks, the source materials of tonsteins from P_2.1 horizon were mostly composed of calc-alkalic, silica-poor volcanic ash (similar to rhyodacitic magma), whereas those from P_2.2+3 were apparently more siliceous and K-rich (rhyolitic magma). Thus, tonsteins from the two different horizons are characterized by unique geochemical properties, which remain constant over a wide lateral extent. Integration of trace-elemental compositions with mineralogical and textural observations makes possible the establishment of tonstein stratigraphy, thus, facilitating more precise and reliable coal-seam correlations.     

Ar-Ar laser dating of tektites from the Cheb Basin (Czech Republic): Evidence for coevality with moldavites and influence of the dating standard on the age of the Ries impact

Moldavites (Central European tektites) are genetically related to the impact event that produced the ∼24-km diameter Ries crater in Germany, representing one of the youngest large impact structures on Earth. Although several geochronological studies have been completed, there is still no agreement among ⁴⁰Ar-³⁹Ar ages on both moldavites and glasses from Ries suevites. Even recently published data yielded within-sample mean ages with a nominal spread of more than 0.6 Ma (14.24-14.88 Ma). This age spread, which significantly exceeds current internal errors, must be in part ascribed to geological and/or analytical causes.This study reports the results of a detailed geochronological investigation of moldavites from the Cheb area (Czech Republic), which have never been dated before, and, for comparison, of two samples from type localities, one in southern Bohemia and the other in western Moravia. We used ⁴⁰Ar-³⁹Ar laser step-heating and total fusion techniques in conjunction with microscale petrographic and chemical characterization. In addition, with the purpose of ascertaining the influence of the dating standards on the age of the Ries impact and making data from this study and literature consistent with the now widely used Fish Canyon sanidine (FCs) standard, we performed a direct calibration of multi-grain splits of the Fish Canyon biotite (FCT-3) with FCs. The intercalibration factors (), determined for eight stack positions in one of the three performed irradiations, were indistinguishable within errors and gave an arithmetic mean and a standard deviation of 1.0086 ± 0.0031 (±2σ), in agreement with previous works suggesting that biotite from the Fish Canyon Tuff is somewhat older (∼0.8%) than the coexisting sanidine.Laser total fusion analysis of milligram to sub-milligram splits of five tektite samples from the Cheb area yielded mostly concordant intrasample ⁴⁰Ar-³⁹Ar ages, and within-sample weighted mean ages of 14.66 ± 0.08-14.75 ± 0.12 Ma (±2σ internal errors, ages relative to FCs) that overlap within errors. These ages match those obtained for samples from western Moravia (14.66 ± 0.08 Ma) and southern Bohemia (14.68 ± 0.11 Ma), supporting the genetic link between Cheb Basin tektites and moldavites, and, consequently, between Cheb Basin tektites and the Ries impact. In contrast to samples from the Cheb area and Moravia, ⁴⁰Ar-³⁹Ar ages from total fusion experiments on the Bohemian specimen ranged widely from ∼14.6 to ∼17.0 Ma. Older apparent ages, however, were systematically obtained from fragments characterized by visible surface alteration. Laser step-heating experiments, although displaying slightly disturbed age profiles, were in line with total fusion analyses and yielded well-defined plateau ages of 14.64 ± 0.11-14.71 ± 0.11 Ma (±2σ internal errors, ages relative to FCs).A thorough comparison of our and previous ⁴⁰Ar-³⁹Ar ages on both moldavites and Ries suevite glasses, recalculated relative to the ⁴⁰Ar^∗/⁴⁰K ratio recently determined for FCs using intercalibration factors available in or derivable from the literature, reveals some inconsistencies which may be ascribed to either geological or analytical causes. Based on our data, decay constants in current use in geochronology, and ages calculated relative to FCs, we infer that the age of moldavites is 14.68 ± 0.11 Ma (±2σ, neglecting uncertainties in the ⁴⁰K decay constants).     

Trace Element Geochemistry of Cenozoic Volcanic Rocks in Shandong Province

The Cenozoic volcanic rock of Shandong Province are mainly alkalic and strongly alkalic basaltic rocks.The Contents of major and trace elements including transitional,incompatible and rare-earth elements were determined.The chemical characterisitics of major and trace elements indicate that these basaltic rocks were derived from a mantle source and probably represent a primary magma,I,e.,unmodifiecd partical melts of mantle peridotite in terms of Mg values,correlatione between P2O5 and Ce,Sr,Ni and Rb concentrations,mantle xenoliths,etc.The abundances of trace elements vary systematically from west to east.The compatible transition elements such as Co,Ni,and Cr show a remarkable depletion,whereas the incompatible and rare-earth elements are abundant as viewed from the chondrite-nor-malized patterns.The chemical composition and correlation are consistent with the tectonic setting.According to the batch and fractional partial melting theory,the trace element contents of Shandong volcanic rocks can be calculated from the two-component mixing model.     

Zones of impact metamorphism in the crystalline rocks of the Nördlinger Ries crater

Fragments of crystalline basement rocks in suevite, a tuff-like breccia found in the area of the Nördlinger Ries crater, display a continuous gradation of metamorphism. This is interpreted as an effect of the shock waves caused by meteoritic impact, the degree of metamorphism reflecting a radial gradient of pressure and temperature diminishing outward from the point of impact. This phenomenon gives further support to the theory that Ries crater is of meteoritic origin and that suevite is not volcanic in nature. A classification of varying impact facies in crystalline rocks is proposed. It is hoped that the system proposed may prove valid for impact structures in other areas.     

羌塘东部治多县直根尕卡一带二叠纪栖霞期火山岩地球化学特征及其构造意义

羌塘东部治多县直根尕卡一带二叠纪栖霞期火山岩主要由中基性火山碎屑岩及熔岩组成,火山岩地球化学研究表明,其主元素表现为高TiO_2和低TiO_2两种特征,球粒陨石标准化稀土配分模式为LREE富集型.MORB标准化的微量元素配分型式为大洋隆起型,显示岩浆形成于板内裂谷构造环境.Sr、Nd、Pb同位素地球化学研究表明火山岩显示明显的亏损地幔源区特征.综合研究表明直根尕卡一带二叠纪栖霞期火山岩形成于大陆边缘拉张构造(或陆缘始裂谷)环境,岩浆起源于地幔,属地幔柱作用的产物.     

新疆北部中二叠统烃源岩地球化学特征与沉积环境

首次对新疆北部准噶尔、吐哈及伊犁盆地中二叠统碳酸盐岩类、泥岩类烃源岩的微量元素、稀土元素和有机地球化学丰度进行了系统分析 ,其主要特征是微量元素含量与同类岩石的克拉克值相比 ,有的较高 ,有的偏低 ;轻稀土富集程度较高 ,重稀土相对较低 ,Ce/ Ce*具有较明显的正异常 ,反映出烃源岩沉积环境总体为还原环境。有机地球化学分析证实 ,烃源岩中微量元素含量对沉积水体中生物的分布有一定的影响 ,部分微量元素丰度与有机质含量呈明显的正相关关系。还原程度强的沉积相带是原始有机质沉积的良好场所 ,沉积有机质能及时沉积、保存 ,烃源岩大多有机质丰度高 ;反之 ,则明显变差     

煤系高岭岩的地球化学判别标志

本文主要研究了煤系高岭岩的微量、稀土、氧同位素地球化学特征。根据高岭岩产出层序、岩石学、矿物学、地球化学特征的研究，将煤系高岭岩分为两类：（１）铝土质高岭岩，微量元素含量、稀土总量，氧同位素值高，稀土配分模式与典型北美页岩相似，Ｅｕ负异常，反映其源岩为风化壳化学风化作用产物。（２）夹矸高岭岩，微量元素含量，稀土总量，氧同位素值低，稀土配分模式部分与典型北美页岩相似，反映其源岩与铝土质高岭岩类似；部     

鄂尔多斯盆地中部上三叠统延长组物源方向分析与三角洲沉积体系

首次利用稀土元素和微量化学元素,分析鄂尔多斯盆地中部上三叠统延长组母岩类型和物源方向。研究表明盆地中部延长组砂岩和泥岩的稀土元素地球化学特征、REE分配模式及微量化学元素蜘蛛图解相同,表现为轻稀土富集,重稀土亏损,铕、铈元素亏损;REE分配模式均呈“右倾斜、LREE富集、HREE平坦”型;微量化学元素蜘蛛图解具“四峰三谷一平台”型,曲线呈阶梯状分布;砂岩和泥岩的地球化学特征、REE分配模式及微量化学元素蜘蛛图解与盆地东北缘的太古代、元古代变质岩相一致,而与火成岩的重稀土富集、轻稀土亏损、“V”字型REE分配模式和“三峰两谷”型、曲线呈“W”字型分布的蜘蛛图解的特征有显著的差别。说明延长组母岩是盆地东北缘的太古代、元古代变质岩,主要物源方向为北东向。依据物源方向、沉积环境、砂岩岩石学特征、砂岩稀土元素和微量化学元素的地球化学特征,将鄂尔多斯盆地中部上三叠统延长组沉积划分为两大三角洲沉积体系,即北东向的安塞三角洲沉积体系、志靖三角洲沉积体系、安边三角洲沉积体系和北西向的盐定三角洲沉积体系。在三角洲沉积体系划分的基础上,详细阐述了不同三角洲沉积体系的岩石学特征、稀土元素和微量化学元素的地球化学特征及延长组长6-长2期三角洲沉积体系的演化过程。     

贺兰山地区晚三叠世延长组地球化学特征及其地质意义

沉积岩的微量和稀土元素对沉积环境变化有着较高的灵敏度,是研究古沉积环境以及沉积物源区构造背景的一种有效手段。本文主要利用地球化学方法对贺兰山晚三叠世延长组不同地区、不同层段的25件泥岩、粉砂岩以及细砂岩样品进行了主量、微量以及稀土元素测试分析,探讨了延长期沉积环境和物源区构造背景。结果显示：延长期整体处于氧化—还原过渡的淡水环境,古气候温暖潮湿;稀土元素球粒陨石标准化配分表现为轻重稀土分异明显,且轻稀土富集、重稀土相对亏损,Eu负异常,Ce异常不明显等特征;La/Yb-REE和La/Th-Hf源岩判别图及Gd/Yb的比值关系图显示延长组源岩主要为长英质岩石,部分为基性岩和沉积岩,且以后太古界为主要物源;La-Th-Sc,Th-Sc-Zr/10和Th-Co-Zr/10判别图解均显示研究区延长组物源区构造背景主要为大陆岛弧,晚期有活动陆缘构造背景的物源加入。     

微量元素和Pb同位素对西藏雅鲁藏布构造带日喀则蛇绿岩形成环境的制约

西藏南部雅鲁藏布构造带分布有一系列蛇绿岩体。人们对这些蛇绿岩体的形成环境仍然存在较大的争议。雅鲁藏布构造带中段日喀则蛇绿岩路曲和大竹曲岩体镁铁质岩石的微量元素和Pb同位素特征指示其母岩浆起源于亏损地幔源区。这些镁铁质岩石的La/Sm和Sm/Yb比值显示其岩浆产生于尖晶石二辉橄榄岩地幔经过大约10%部分熔融作用。综合岩相学和全岩主量元素特征暗示这些镁铁质岩石形成于无水玄武质岩浆。而且这些镁铁质岩石的微量元素和REE元素配分模式均非常相似于N-MORB,除了弱Nb-Ta负异常。这些特征表明路曲和大竹曲岩体形成于大洋中脊环境。此外,路曲和大竹曲镁铁质岩石的Pb同位素结果指示其地幔源区与印度洋MORB地幔域具有相似的地球化学特征。这些镁铁质岩石N-MORB标准化微量元素模式显示弱Nb-Ta负异常可能是由于其地幔源区交代了古老的俯冲带物质。     

山西阳泉三矿煤层粘土岩夹矸地球化学特征

采用化学法和中子活化(INAA)法对采自山西阳泉三矿山西组3号煤层和太原组12号煤层的3件煤层夹矸粘土岩样品的8种常量元素(氧化物)和33种微量元素含量进行了测定。通过对具有示踪意义的元素及其比值的对比分析,3个样品总体上均不具有典型的沉积岩特征,应该是由酸性或酸性偏碱性火山物质(降落的或陆源搬运的)在地表覆水较浅的弱氧化条件下经原地淋滤、蚀变形成的。原岩蚀变程度较高,不稳定或较不稳定的元素大量流失,甚至一些较稳定的元素(如高岭岩中的铁、锰)也明显流失。强烈的化学蚀变以及岩石中矿物成分的变化是造成粘土岩间以及粘土岩与原岩间元素(尤其是REE)含量及REE配分模式差异的主要原因。      

云南兰坪盆地古近系细碎屑岩地球化学特征及其地质意义

采用电感耦合等离子体质谱(ICP-MS)方法对兰坪盆地古近系104件细碎屑岩样品进行了稀土元素及微量元素分析,结果显示∑LEE含量较高,轻稀土含量较富集、重稀土含量较亏损,显示出明显的"右倾"型配分模式。根据稀土元素和微量元素特征、w(Zr)-w(Th)、La-Th-Sc、Th-Sc-Zr/10等多种沉积构造背景判别图解及多种交叉分析方法,对兰坪盆地古近系细碎屑源岩构造背景进行了详细研究。利用La/Th-Hf和La/Yb-∑REE判别图解对兰坪盆地古近系源岩属性进行了分析,结果表明:兰坪盆地古近系碎屑源岩主要以上地壳长英质岩石为主,并混有少量基性岩,反映其物源区构造背景为早期为大陆岛弧构造背景,至晚期逐渐过渡为被动大陆边缘构造背景。     

库车坳陷第三系泥岩地球化学特征及其对构造背景和物源属性的指示

利用碎屑岩地球化学特征判断沉积盆地的构造背景和物源属性是盆地分析的重要手段，也是对利用粗碎屑沉积岩的组分统计判断盆地源区背景的有益补充和验证。对库车坳陷第三系36件泥岩样品的地球化学特征分析表明，主量元素中CaO的含量很高，对其他主量元素以及微量和稀土元素有稀释作用，一些可靠的物源分析指标主要指示了非碳酸盐沉积物的源区性质；REE分布模式与上地壳相似，轻稀土元素富集，Eu负异常，微量元素比值显示源岩以长英质岩石为主。通过K2O／Na20-SiO2以及La-Th-Sc和Th-Sc-Zr／10判别图分析，认为源区的构造背景具有类似于岛弧的特征。这一结果与前人所做的砂岩组分的研究结果存在差异，说明板内造山带与其前陆盆地之间在沉积与构造耦合上具有特殊性。