东海表层沉积物黏土粒级中多态脂肪酸组成与地球化学特征

对东海陆架泥质沉积区两个代表性站位表层沉积物开展了黏土粒级分离提取,并对其依次进行溶剂萃取、碱解和酸解处理,得到结合程度不同的三种脂肪酸组分：有机溶剂抽提的游离态脂肪酸、碱解得到的碱解酸和酸解得到的酸解酸。三种赋存态酸的存在表明它们所联结的宏观分子的结构不同或所吸附黏土矿物的保护作用不同。不同赋存态酸的数量、组成和分布有一定差异,两站位相同赋存态酸的数量与组成也存在明显差异。组成与分布特征表明东海陆架泥质区超细颗粒物中脂肪酸以海洋内源藻类来源为主（〉70％）,陆源高等植物贡献相对较低,并有少量的细菌源贡献。各赋存态酸的降解程度为碱解酸高于酸解酸高于游离酸,可能与其在黏土中的赋存状态和吸附过程有关。靠近长江河口的表层沉积物样品（24站）海洋内源藻类贡献略低于远离河口的站位（30站）,陆源高等植物的输入稍高于后者,是受两泥质区沉积环境综合影响的结果。     

Revision of the conchostracan genera Cratostracus and Porostracus from Cretaceous deposits in north-east China

The diagnoses of the conchostracan genera Cratostracus and Porostracus are revised following a re-examination of their type species under a scanning electron microscope. In Cratostracus each growth line has a serrated lower margin. Radial lirae branch into smaller ridges that merge with each other to give the upper part of each growth band in the ventral region of the carapace a slightly undulating surface. Cross-bars are present between these lirae. In Porostracus the radial lirae on the growth bands near the umbo are long and relatively widely spaced. There is a fine reticulum between them in the umbonal part of the carapace and cross-bars on the ventral surface. The ornament of Porostracus indicates that it can be assigned to the family Halysestheriidae rather than to the Afrograptidae, in which it has been placed previously. Morphological analysis of most of the species of the two genera and closely related Orthestheria (Migransia) under the scanning electron microscope is required before their stratigraphic potential can be fully realized.     

Pyrolysis of immature Torbanite and of the resistant biopolymer (PRB A) isolated from extant alga Botryococcus braunii. Mechanism of formation and structure of torbanite

Immature Torbanite and the resistant biopolymer (PRB A) isolated from extant B. braunii were previously compared using bulk spectroscopic methods. In the present work, analysis of 400°C pyrolysis products and pyrolysis residues provided further information on their structure and possible relationships. It appears that such polymers are based upon unbranched, saturated, cross-linked hydrocarbon chains up to C₃₁. In addition to these bridging structures, a substantial part of the alkyl chains is singly bound, as esters of unbranched, saturated or cis unsaturated, even fatty acids. These esters are sterically protected, against chemical degradations, by the network of the bioand geopolymer.Quantitative and qualitative observations derived from 400°C pyrolysis confirm that the chemical structure of PRB A and immature Torbanite are closely related. The pyrolysis residues show a similar evolution and numerous common features are noted, with respect to the nature and the distribution of the major constituents of the pyrolysates (hydrocarbons and fatty acids). Accordingly, Botryococcus provides what seems to be the first example of a close structural relationship between a biopolymer produced in large amounts by an extant alga and the geopolymer of an immature kerogen. The essential role of PRB A in Torbanite formation is ascertained. Moreover, it is found that the resistant biopolymer does not undergo important structural changes during the first stages of diagenesis. Thus, owing to steric protection, the esters of immature Torbanite show a distribution quite close to the one of PRB A esters, with exclusively even constituents and a large contribution of unsaturated acids.Recent observations pointed to the possible genesis of some algal kerogens principally by selective preservation of resistant macromolecules. Such a type of formation is clearly predominant in Torbanite, where the bulk of the fossil organic matter corresponds to a selectively preserved and weakly altered, resistant biopolymer, while incorporation of lipids into the kerogen structure during diagenesis seems to play a minor role.     

Molecular and stable carbon isotopic compositions of saturated fatty acids within one sedimentary profile in the Shenhu,northern South China Sea: Source implications

This study examined the distributions and stable carbon isotopic compositions of saturated fatty acids (SaFAs) in one 300 cm long sedimentary profile, which was named as Site4B in Shenhu, northern South China Sea. The concentrations of total SaFAs in sediments ranged from 1.80 to 10.16 μg/g (μg FA/g dry sediment) and showed an even-over-odd predominance in the carbon chain of C₁₂ to C₃₂, mostly with n-C₁₆ and n-C₁₈ being the two major components. The short-chain fatty acids (ScFAs; n-C₁₂ to n-C₁₈) mainly from marine microorganisms had average δ¹³C values of −26.7‰ to −28.2‰, whereas some terrigenous-sourced long-chain fatty acids (LcFAs; n-C₂₁ to n-C₃₂) had average δ¹³C values of −29.6‰ to −34.1‰. The other LcFAs (n-C₂₄ & n-C₂₆ ∼ n-C₂₈; average δ¹³C values are −26.1‰ to −28.0‰) as well as n-C₁₉ and n-C₂₀ SaFAs (average δ¹³C values are −29.1‰ and −29.3‰, respectively) showed a mixed signal of carbon isotope compositions.The relative bioproductivity calculation (marine vs. terrigenous) demonstrated that most of organic carbon accumulation throughout the sedimentary profile was contributed by marine organism. The high marine productivity in Shenhu, South China Sea may be related to the hydrocarbon seepage which evidenced by diapiric structures. Interestingly, there is a sever fluctuation of terrigenous inputs around the depth of 97 cm below the seafloor (bsf), probably resulting from the influence of the Dansgaard–Oeschger events and the Younger Dryas event as revealed by ¹⁴C age measurements.     

Zalesskioxylon xiaheyanense sp. nov., a gymnospermous wood of the Stephanian (Late Pennsylvanian) from Ningxia, northwestern China

A new Late Pennsylvanian species of gymnospermous fossil wood, Zalesskioxylon xiaheyanense sp. nov. is described from the Lower Taiyuan Formation (Stephanian B-C) near the village of Xiaheyan, Ningxia Hui Autonomous Region, northwestern China. The specimen consists only of silicified secondary xylem. The tracheids are pycnoxylic with 2–3 seriate bordered pits, arranged in subcircular or hexagonal alternate (araucaroid) pattern. The pores of the pits are small, linear, and regularly tilted. Xylem rays are homogeneous, uniseriate, 1–25 cells high. Cross-fields are filled with numerous mixed simple pits of various sizes. Growth rings, axial parenchymatous elements and resin canals are absent. The geographic distribution of Zalesskioxylon woods is reviewed. Zalesskioxylon xiaheyanense sp. nov. grew at low latitudes, and because of the lack of growth rings, probably lived under relatively uniform climatic conditions. Our new species supplements the poorly known distribution of Carboniferous wood in China.     

Geochronology of Ailuropoda–Stegodon fauna and Gigantopithecus in Guangxi Province, southern China

Pleistocene faunas from south China are difficult to subdivide based on the long temporal ranges of many taxa and a reduced number of genera in comparison to faunas from temperate north China. In south China, the Ailuropoda–Stegodon fauna is a very general one and includes a relatively stable suite of genera that apparently persisted for long periods of time. These attributes have made constraining its time range difficult. Application of electron spin resonance (ESR) dating of tooth enamel constrains the ages well where uranium uptake was minor. Where uranium uptake into teeth was significant, an approach combining ESR and ²³⁰Th/²³⁴U isotopic analysis also yields excellent ages. Previous estimates of early, middle and late Pleistocene time ranges previously determined by biostratigraphic seriation for the Ailuropoda–Stegodon fauna are confirmed in all cases but are made more precise with our approach, including specific time ranges for certain archaic taxa. Absolute dating also yields an extended time range for Gigantopithecus blacki of 1200 to 310 ka.     

柴北缘锡铁山一带榴辉岩的岩石学特征及其退变PT轨迹

柴北缘锡铁山地区榴辉岩以透镜体的形式存在于花岗质片麻岩和副变质片麻岩中.根据矿物组合的不同,可以分为多硅白云母榴辉岩和角闪石榴辉岩.在多硅白云母榴辉岩中首次发现了柯石英假象.利用榴辉岩中Grt-Cpx-Phn矿物温压计.结合绿辉石中存在柯石英假象包体的现象,得到锡铁山榴辉岩的峰期温压条件为751～791℃,2.71～3.17GPa,证明了锡铁山地区与柴北缘其他地块一样,也经历了超高压变质作用.通过PT视剖面图计算了榴辉岩退变的PT轨迹具有2个阶段演化特征：即先等温降压,然后再降温降压的PT轨迹.详细的岩石学研究探讨了榴辉岩在退变过程中,各矿物的成分和结构的改变过程.石榴石在等温降压过程中成分变化不大,而在角闪石出现后,其边部镁铝榴石含量明显降低,进而形成了韭闪石+斜长石的冠状体.绿辉石在水饱和状态下经过贫硬玉化改造,而后形成了Di+Ab+Amp的后生合晶.多硅白云母分解形成白云母+黑云母及少量石英及钾长石的组合.角闪石随着温压条件的降低由钠钙质闪石逐渐向钙质闪石转化.     

Bayeritheca hughesii gen. et sp. nov., a new Eucommiidites -bearing pollen organ from the Cenomanian of Bohemia

A new pollen organ, Bayeritheca hughesii gen. et sp. nov. with in situ Eucommiidites pollen grains, is described from the Cenomanian of Bohemia in Central Europe. It is based on a single lignified specimen which is the largest Eucommiidites -producing pollen structure described so far. It shows whorls of microsporangiate units attached to a massive main axis forming a cone-like structure. Each microsporangiate unit forms distally an angular head bearing trichomes and centrally arranged mucronate tubercles. The head is attached to a short stalk. Proximal sides of heads display radially arranged synangia. Each synangium contains an unknown number of pollen sacs with numerous Eucommiidites pollen grains.Bayeritheca is the only genus of Erdtmanithecales in which synangia instead of sporangia are found. Bayeritheca differs from Eucommiiditheca Friis & Pedersen in the whorled arrangement of microsporangiate units, which are densely spaced forming a cone-like structure. It differs from Erdtmanitheca Pedersen, Crane & Friis in the elongate shape of the whole organ, slender main axis, shorter pollen sacs, and different Eucommiidites pollen.     

Revision of the conchostracan genus Estherites from the Upper Cretaceous Nenjiang Formation of the Songliao Basin and its biogeographic significance in China

The diagnosis of Estherites corrugatus from the basal part of the Coniacian Second Member of the Nenjiang Formation in Nenjiang County, north-east China is revised following the application of a new preparation technique to some of the carapaces and an examination of specimens under a scanning electron microscope, both of which revealed morphological features on the carapace that had not been recognized previously. Restudy of the type species of the two subgenera Estherites (Euestherites) and Estherites (Parestherites) also revealed details of carapace features not seen hitherto. These indicate that they should be separated from Estherites. As a result, Euestherites is upgraded to genus level and Parestherites is placed in synonymy. The importance of Estherites and Euestherites is considered in the context of Late Cretaceous assemblages of these crustaceans and the three conchostracan provinces (South-West, South-East and North China) that are recognized to have been present in China during the Turonian–Santonian period.     

Isotopic fractionation associated with biosynthesis of fatty acids by a marine bacterium under oxic and anoxic conditions

Shewanella putrefaciens (Strain MR-4), a gram negative facultative marine bacterium, was grown to stationary phase under both aerobic and anaerobic conditions using lactate as the sole carbon source. Aerobically-produced cells were slightly enriched in ¹³C (+1.5‰) relative to the lactate carbon source, whereas those from anaerobic growth were depleted in ¹³C (−2.2‰). The distribution of fatty acids produced under aerobic conditions was similar to that resulting from anaerobic growth, being dominated by C_16:1 ω7 and C_16:0 fatty acids with a lesser amount of the C_18:1 ω7 component. Low concentrations of saturated even numbered normal fatty acids in the C₁₄ to C₁₈ range, and iso-C_15:0 were synthesized under both conditions. Fatty acids from anaerobic cultures (average δ¹³C=−37.8‰) were considerably depleted in ¹³C relative to their aerobically-synthesized counterparts (−28.8‰). The distinct differences in isotopic composition of both whole cells and individual fatty acid components result from differences in assimilation pathways. Under aerobic conditions, the primary route of assimilation involves the pyruvate dehydrogenase enzyme complex which produces acetyl-CoA, the precursor to lipid synthesis. In contrast, under anaerobic conditions formate, and not acetate, is the central intermediate in carbon assimilation with the precursors to fatty acid synthesis being produced via the serine pathway. Anaerobically-produced bacterial fatty acids were depleted by up to 12‰ relative to the carbon source. Therefore, detection of isotopically depleted fatty acids in sediments may be falsely attributed to a terrestrial origin, when in fact they are the result of bacterial resynthesis.     

Neogastroplites meets Metengonoceras: morphological response of an endemic hoplitid ammonite to a new invader in the mid-Cretaceous Mowry Sea of North America

High levels of morphological variability have been attributed to various ecological and developmental mechanisms, including selection for ecological generalists in an unstable environment, inherent developmental plasticity, and the absence of competitors in an empty ecosystem. The late Albian–early Cenomanian hoplitid ammonite Neogastroplites of the Mowry Sea of North America, notorious for its extreme levels of intraspecific variability, is used as a test case of the idea that a lack of competitors promotes variability. The group responded to the invasion of a second ammonite, the engonoceratid Metengonoceras, into the Mowry Sea by spreading into a previously unoccupied region of morphospace, suggesting possible ecological character displacement and a release from constructional constraints. However, morphological variability did not decrease, as would be predicted by the competition model. The variability of Neogastroplites might instead result from environmental instability or developmental flexibility.     

Palynodinium minus sp. nov., a new dinoflagellate cyst from the Cretaceous–Paleogene transition in New Zealand; its significance and palaeoecology

This is the first record of a representative of the organic-walled dinoflagellate cyst genus Palynodinium from the New Zealand region. Previously, Palynodinium grallator has been reported from two sites in offshore Tasmania during Ocean Drilling Program, Leg 189. The new species Palynodinium minus is found consistently in latest Maastrichtian? and earliest Danian strata (latest Haumurian–earliest Teurian) in two sections located along the mid-Waipara and Grey rivers, North Canterbury, South Island. It occurs in a narrow stratigraphic interval at the Cretaceous–Paleogene transition and is potentially a stratigraphically important index species in the region. Its range coincides with that of the global earliest Danian index fossil Carpatella cornuta and a basal Danian acme interval of Trithyrodinium evittii, and is correlated to ca. 65.5–65.2 Ma. Its highest occurrence is at the base of an acme interval of Palaeoperidinium pyrophorum. It has only been recorded from sections composed of siliciclastic shelf sediments, suggesting that it might have had a palaeoecological preference for relatively near-shore environments.     

滇西勐库退变质榴辉岩的P-T-t轨迹及地质意义

滇西双江县勐库地区的退变质榴辉岩经历了多期退变质作用的改造,早期的平衡共生矿物组合难觅踪迹。应用传统的石榴石-单斜辉石(GC)温度计、石榴石-单斜辉石-多硅白云母(GCP)压力计进行变质作用的PT条件估算存在许多不确定性。本文应用魏春景等(2009)依据MORB成分计算的PT视剖面图上多硅白云母、石榴石、绿辉石的成分随体系中PT条件的变化情况,估算了进变质的P=2.00~2.30GPa,T=420~460℃,相当于硬柱石蓝片岩相—硬柱石-蓝闪石榴辉岩相;峰期变质的P=3.35~4.46GPa,T=530~610℃,相当于硬柱石榴辉岩相;早期退变质的P=2.00~2.50GPa,T=470~540℃,相当于硬柱石-蓝闪石榴辉岩相;中期退变质的P=0.95~1.43GPa,T=700~750℃,相当于角闪石榴辉岩相-高压麻粒岩相。晚期退变质作用以出现大量的闪石类矿物为特征,可划分为3个阶段,并显示了持续的降温、降压过程。结合区域地壳演化进程,本文详细讨论了上述P-T-t轨迹的地质意义。     

Evidence for geographic variation in the diets of late Pleistocene and early Holocene Bison in North America, and differences from the diets of recent Bison

During the late Pleistocene and early Holocene, Bison was widely dispersed across North America and occupied most regions not covered by ice sheets. A dietary study on Bison paleopopulations from Alaska, New Mexico, Florida, and Texas was performed using two methods that relate dental wear patterns to diet, mesowear analysis and microwear analysis. These data were compared to a mixed sample of extant Bison from the North American central plains, extant wood Bison from Alberta (Canada) and a variety of other modern ungulates. Mesowear relates macroscopic molar facet shape to levels of dietary abrasion. The mesowear signature observed on fossil Bison differs significantly from the hyper-abrasive grazing diet of extant Bison. Tooth microwear examines wear on the surface of enamel at a microscopic scale. The microwear signal of fossil samples resembles to modern Bison, but the fossil samples show a greater diversity of features, suggesting that fossil Bison populations regularly consumed food items that are texturally inconsistent with the short-grass diet typical of modern plains Bison. Mesowear and microwear signals of fossil Bison samples most closely resemble a variety of typical mixed feeding ungulates, all with diets that are substantially less abrasive than what is typical for modern plains Bison. Furthermore, statistical tests suggest significant differences between the microwear signatures of the fossil samples, thus revealing geographic variability in Pleistocene Bison diets. This study reveals that fossils are of value in developing an understanding of the dietary breadth and ecological versatility of species that, in recent times, are rare, endangered, and occupy only a small remnant of their former ranges.     

榴辉岩中传统地质温压计新解：来自PT视剖面图的证据

石榴石-单斜辉石(GC)温度计和石榴石-单斜辉石-多硅白云母(GCP)压力计是确定榴辉岩形成温压条件的最常用方法,二者主要依据石榴石、绿辉石和多硅白云母中相组分之间的交换和转换变质反应.依据MORB成分计算的PT视剖面图表明,在不同榴辉岩矿物组合中,控制3个矿物相成分变化的相组分之间的变质反应不同.在低温含绿泥石、滑石和蓝闪石榴辉岩组合中,石榴石和绿辉石的镁含量主要受到含水矿物脱水反应的控制,并都随温度升高而升高,二者之间的铁镁交换反应并不起主要作用.因此,在自然界含有蓝闪石等含水矿物的低温榴辉岩中,由于绿辉石相对富镁而常常导致GC温度计结果偏低.在含有硬柱石的高压-超高压榴辉岩中,石榴石中的钙含量受到硬柱石的控制,随着压力升高或温度降低,硬柱石含量增加,使石榴石中钙降低,此时石榴石-绿辉石-多硅白云母之间的转换反应对石榴石成分的影响会很微弱,由于石榴石相对贫钙而导致GCP压力计结果偏低.在含有蓝晶石的中温高压-超高压榴辉岩中,矿物成分的变化受到石榴石-绿辉石之间的铁镁交换反应和石榴石．绿辉石．多硅白云母-蓝晶石-石英/柯石英之间的一系列转换反应控制,因此,GC和GCP温压计都能给出相对合理的结果.在低压普通角闪石榴辉岩中,石榴石和绿辉石中的镁含量主要反应压力变化,有时并不指示变质作用温度.在含有蓝闪石等含水矿物的低温榴辉岩中,Thermocalc程序中的平均温压(avPT)方法可以给出比较合适的温度,但压力结果与GCP压力计一样也会偏低一些.在蓝闪石和绿帘石等含水矿物消失后的中温蓝晶石榴辉岩中,avPT方法难以给出合理的PT信息.相对来说,视剖面图方法能够给出最多的PT信息,是目前确定变质岩PT条件的最好方法.     

华南云开高州紫苏花岗岩及其两类石榴石的成因：岩石学和锆石U-Pb年代学证据

云开地块早古生代的构造背景至今仍存有争论。对云炉-龙修一带出露的含石榴石紫苏花岗岩进行研究可为该区构造-变质演化提供重要制约。详细的岩相学研究表明紫苏花岗岩中存在两种成因的石榴石(石榴石Ⅰ和石榴石Ⅱ),并识别出该岩石保留了三阶段演化的矿物组合(M_1-M_3)。峰期前矿物组合(M_1)由紫苏辉石变斑晶中的包裹体矿物石榴石+黑云母+斜长石+钛铁矿+石英组成。峰期变质-深熔矿物组合(M_2)由基质中平衡共生的斑晶矿物石榴石Ⅰ+紫苏辉石+黑云母+石英+斜长石+钛铁矿构成。退变质矿物组合(M_3)以紫苏辉石和黑云母以及钛铁矿边部降温生成石榴石Ⅱ+石英冠状体("红眼圈")和黑云母+石英后成合晶为特征。传统地质温压计、平均温压法及在NCKFMASHTO模式体系下的相平衡模拟结果表明,紫苏花岗岩峰期前矿物组合形成条件为720℃/70kbar(M1),峰期变质-深熔结晶条件为835～810℃/65～58kbar(M_2),退变质条件为740℃/56kbar(M_3)。岩相观察和P-T计算结果表明紫苏花岗岩的形成可能反映了一条顺时针的P-T轨迹,且以峰期前略微减压并伴随明显的升温和峰期后具有近等压冷却(IBC)过程为特征。LA-ICP-MS锆石U-Pb年代学结果显示锆石核部加权平均年龄为～431Ma,锆石边部加权平均年龄为～243Ma。我们认为峰期深熔作用和岩浆结晶石榴石Ⅰ的形成可能发生于早古生代(加里东期),而晚期退变质作用和变质重结晶石榴石Ⅱ的形成可能发生在早中生代(印支期)。本研究也表明云开地区含石榴石紫苏花岗岩的形成与早古生代扬子和华夏陆块碰撞后抬升过程有紧密联系,并遭受了早中生代印支期构造热事件的明显叠加。     

北大别饶拔寨石榴辉石岩P-T-t轨迹及其构造意义

P-T-t轨迹作为变质岩的重要研究方法之一，对揭示岩石的构造演化过程具有重要意义。北大别饶拔寨镁铁-超镁铁岩形成的构造环境和就位过程长期以来尚存争议。本文通过岩相学观察、矿物化学研究和温压计计算，揭示出饶拔寨石榴辉石岩经历了四个变质演化阶段：1）超高压变质阶段（M1）：主要根据石榴子石中金红石的出溶，单斜辉石中石英的出溶和磷灰石中不透明矿物的出溶，结合前人研究，认为饶拔寨石榴辉石岩经历过超高压变质阶段（≥2.5GPa）；2）高压麻粒岩相阶段（M2）：矿物组合为石榴子石（变斑晶）和单斜辉石（基质）+斜长石（基质），记录的温压条件为T=648~700℃，P=1.47~1.94GPa；3）中压麻粒岩相阶段（M3）：以石榴子石外围发育的主要由斜方辉石+斜长石组成的内圈"白眼圈"为特征，形成的温压条件为T=781~796℃，P=0.92~0.98GPa；4）角闪岩相阶段（M4）：以石榴子石变斑晶周围发育的外圈"白眼圈"为特征，其矿物组合为角闪石+斜长石的后成合晶，形成的温压条件为T=663~685℃，P=0.50~0.58GPa。石榴辉石岩的锆石SIMS U-Pb定年得到了3组不同的交点年龄，分别为208.1~202.1Ma、227.6Ma和817.7Ma。根据锆石包裹体中角闪石+斜长石的组合，推断208.1~202.1Ma代表了角闪岩相变质年龄的下限，227.6Ma则是高压麻粒岩相的下限年龄，而新元古代年龄（817.7Ma）与区域上的变质岩原岩年龄一致，可能代表了其原岩年龄。结合前人研究，饶拔寨石榴辉石岩记录了顺时针的P-T-t轨迹，揭示了板片俯冲（超高压变质）-碰撞-折返（降压升温过程，~227Ma）-抬升（降压降温过程，208~202Ma）的完整过程。     

1982~2022年《矿床地质》载文分析与趋势展望

《矿床地质》是中国报道矿产资源最新研究成果的代表性刊物,同时也是汇集矿床学领域重要研究进展及成果的学术交流平台,对其载文热点追踪及期刊量化评价有助于梳理国内矿床学领域的研究进展,探究未来发展趋势,并为学科相关研究人员提供借鉴和参考。文章基于文献计量学研究、借助大数据和机器学习等手段,分析了1982~2022年《矿床地质》刊载论文的内容与信息,揭示矿床学40年的研究热点及主题演化情况,并通过与国际同领域知名期刊的对比,系统性地总结和讨论其展现的研究领域的进展和发展趋势。该刊主要聚焦于地球科学领域,热点关键词主要包括：流体包裹体、成矿作用、矿床成因、成矿流体和地质特征等。历年刊文可归纳为5个研究主题,包括区域成矿规律、成矿背景与构造环境、成矿流体和矿化特征、成岩成矿年龄和岩浆热液成矿作用以及元素富集成矿。热门地区主要是内蒙古、新疆和西藏等中西部省区。未来矿床学研究将会更加注重新技术和新方法的宏观和微观应用、多学科交叉融合对矿床成因机制和成矿规律的揭示,以及矿产勘查的综合指导等方面。     

Similar morphological and chemical variations of Gloeocapsomorpha prisca in Ordovician sediments and cultured Botryococcus braunii as a response to changes in salinity

Most Ordovician source rocks consist of accumulation of a colonial marine microorganism, Gloeocapsomorpha prisca (G. prisca) whose nature, ecology and affinity with extant organisms have been in dispute for years. Furthermore, recent studies have shown major differences in phenol moieties between two G. prisca-rich samples. Examination of five G. prisca-rich kerogens by electron microscopy and pyrolysis studies revealed (i) the occurrence of two markedly distinct “morpho/chemical” types: a “closed/phenol-rich” type (Baltic samples) and an “open/phenol-poor” one (North American samples) and (ii) the selective preservation of the resistant micromolecular material building up the thick cell walls in the original organism. Comparison with extant Botryococcus braunii (a widespread green microalga) grown on media of increasing salinity suggests that G. prisca is likely to be a planktonic green microalga related to B. braunii, which can adapt to large salinity variations which, in turn, control its polymorphism. The large differences in colony morphology and in the content of phenol moieties observed in fossil G. prisca and the resulting occurrence of two “morpho/chemical” types, should therefore reflect depositional environments with different salinities. The presence of thick, highly aliphatic, resistant walls in G. prisca selectively preserved during fossilization, accounts for the major contribution of this organism to Ordovician organic-rich sediments and for the resulting typical signature of Ordovician oils.