下扬子区二叠纪主要岩石类型成因的地球化学信息

作者在全面了解陆相层序地层学研究现状的基础上,认为陆相层序及体系域发育仍受控于湖平面相对变化。构造、气候及沉积物供给的控制作用最终通过湖平面变化表现出来。而湖平面变化可分完整旋回与不完整旋回两种情况,进而提出了所形成的层序及体系域模式：在完整旋回中形成了湖泊充填、湖泊扩张、湖泛和湖泊萎缩四个体系域,对应层序为Ⅰ型层序;在不完整旋回中形成了湖泊充填、湖泊扩张、湖泛三个体系域,或者湖泊扩张、湖泛、湖泊萎缩三个体系域,对应层序为Ⅱ型层序。以松辽盆地西部斜坡实际工作为例,提出了中生代层序及体系域划分方案,较前人研究有新认识。     

二叠纪海平面变化研究

在研究全球不同地区二叠纪沉积、层序及生物资料基础上,通过全球诸大陆典型剖面层序划分和对比表明,二叠纪至少有６次海平面升降事件具全球对比意义。二叠纪全球海平面旋回曲线,在不同板块不同成因盆地,其形态及结构不同,但总体可分为两种类型或分支：一是以海相→陆相沉积序列为主的反映主体海平面下降的经典型或欧美型;二是以海相碳酸盐岩→碳酸盐－硅质岩沉积序列为特征的揭示主体海平面上升的特拉斯型或华南型。这与二叠纪特定的全球构造－古地理密切相关。     

Upper Cretaceous Magmatic Series and Associated Mineralisation in the Carpathian – Balkan Orogen

Abstract: The Alpine Orogen contains in South East Europe, from the Carpathians to the Balkans–Srednogorie, an Upper Cretaceous, ore bearing igneous belt: a narrow elongated body which runs discontinously from the Apuseni Mountains in the North, to the western part of the South Carpathians (Banat) in Romania, and further South to the Carpathians of East Serbia and still further East to Srednogorie (Bulgaria). This results in a belt of 750 km/30–70 km, bending from N-S in Romania and Serbia, to E-W in Bulgaria. Using the well established century-old terminology of this region, we describe it in this paper as the Banatitic Magmatic and Metallogenetic Belt (BMMB). Plate tectonics models of the Alpine evolution of South East Europe involve Mesozoic rifting, spreading and thinning of the continental crust or formation of oceanic crust in the Tethian trench system, followed by Cretaceous-Tertiary convergence of Africa with Europe and opening of Eastern Mediterranean and Black Sea troughs. The result of successive stages in the collision process is not only the continental growth of Europe from N to S by the docking of several microplates formerly separated from it by Mesozoic palaeo–oceans, but also the rise of mountain belts by overthickening of the crust, followed by orogenic collapse, lateral extrusion, exhumation of metamorphic core complexes and post-collisional magmatism connected to strike-slip or normal faulting. The BMMB of the Carpathian-Balkan fold belt is rich in ore deposits related to plutons and/or volcano-plutonic complexes. Serbian authors have proposed an Upper Cretaceous Paleorift in Eastern Serbia for the Timok zone and some Bulgarian geologists have furnished geologic, petrological and metallogenetic support for this extensional model along the entire BMMB. The existence and importance of previous westwards directed subductions of Transilvanides (=South Apuseni = Mure? Zone) and Severin-Krajina palaeo–oceans, popular in Roman ian literature, seems to have little relevance to BMMB generation, but the well documented northwards directed subduction of the Vardar-Axios palaeo–ocean during Jurassic and Lower Cretaceous is a good pre-condition for the generation, during the Upper Cretaceous, of banatitic magmas in extensional regime, by mantle delamination due to slab break–off. Four magmatic trends are found: a tholeiitic trend, a calc-alkaline trend, a calc-alkaline high–K to shoshonitic trend and, restricted to East Srednogorie, a peralkaline trend. For acid intrusives, the typology is clearly I-type and magnetite–series, pointing to sources in the deep crust or the mantle; however, some high ⁸⁷Sr/⁸⁶Sr ratios recorded in banatites prove important contamination from the upper crust. The calc-alkaline hydrated magmas, most common for banatitic plutons, can be considered as recording three stages of evolution: more primitive – the monzodioritic, dioritic to granodioritic trend (S Apuseni, S Ba–nat, Timok, C and W Srednogorie); more evolved – the granodioritic-granitic trend (N Apuseni, N Banat, Ridanj–Krepoljin); the alkaline trend (E and W Srednogorie, western part of N Banat). Correlating the composition of the host plutons with the types of mineralisation, several environments can be found in the BMMB, function of timing of fluid separation (porphyry versus non-porphyry environments), depth of emplacement, size of intrusion and geology of intruded rock pile, biotite versus hornblende crystallisation, involving the evolution of K/Na ratio in fluids, i. e. development of potassic and phyllic alteration zones: a) non-porphyry environment with granodioritic to granitic magmas, plutonic level, skarn mineralisation prevails; b) porphyry environment with monzodioritic or dioritic to granodioritic magmas, subvolcanic–hypabyssal–plutonic level; porphyry Cu with skarn halo at hypabyssal-subvolcanic level; c) porphyry environment with monzodioritic or dioritic to granodioritic magmas, volcano-plutonic complexes with porphyry copper plus massive sulfide mineralisation at subvolcanic-volcanic level; d) non-porphyry environment with magmas of alkaline tendency, volcanic level, vein (“mesothermal” and “epithermal”) mineralisation.     

贵州二叠纪——三叠纪古气候和古海洋环境的地球化学研究

通过对贵州二叠纪和三叠纪地层沉积岩相、古生物组合、稀土元素、碳氧同位素和微量元素地球化学综合研究,发现贵州二叠纪、早一中三叠世和晚三叠世三个地质时期古气候和古海洋环境有明显差别。其中二叠纪为潮湿的热带海洋性气候,海水相对氧化,盐度正常,平均温度为53℃;早一中三叠世为干燥的大陆性气候,海水相对还原,盐度较高,平均温度为38℃;晚三叠世又转变为潮湿的气候,海水相对氧化,盐度正常,平均温度为44℃。,结合泛大陆演化特征,讨论了造成气候变化的原因。     

Age and Tectonic Significance of the Mafic Dyke Swarm in the Kuruktag Region, Xinjiang

The mafic dykes are composed of a series of northwest-trending diabase in Kuokesu of the Kuruktag region, Xinjiang. Four whole-rock samples of the mafic dykes in the region give an 40Ar / 36Ar-40K/ 36Ar isochron age of 282 Ma with the initial 40Ar/ 36Ar = 507. The characteristics of the major, trace and rare earth elements of the dyke rocks indicate that they belong to the calc-alkaline series and were emplaced in extensional structures at an intermediate depth of the crust. This shows that there was a large-scale extension in the Permian Period, which might be associated with the post-collisional extension of the ancient Tianshan Mountains.     

内蒙巴彦浩特盆地东部上石炭统靖远组孢子花粉

巴彦浩特盆地的上石炭统靖远组与羊虎沟组为连续沉积,厚度４７７．５ｍ。经２９块岩样分析鉴定,发现孢子花粉５１属９５种（含２新种）和３粒不能鉴定的分子。根据孢粉的纵向演化,可分为上下两个组合带,下组合：Ｔｒｉｐａｒｔｉｔｅｓｖｅｔｕｓｔｕｓ－Ｔｒｉｑｕｉｔｒｉｔｅｓｔｒｉｂｕｌａｔｕｓ组合（简称ＶＴ带）,分布于巴参２井３７７９～３５７０ｍ井段,该孢子带具环孢类含量较低,未发现单缝孢Ｌａｅｖｉｇａｔｏｓｐｏｒｉｔｅｓ和Ｐｕｎｃｔａｔｏｓｐｏｒｉｔｅｓ以及不能归类的Ｔｒｉｎｉｄｕｌｕｓｄｉａｍｐｈｉｄｉｏｓ;上组合：Ｓｉｎｕｓｐｏｒｅｓｓｉｎｕａｔｕｓ—Ｃｒａｓｉｓ－ｐｏｒａｋｏｓａｎｋｅｉ组合（简称ＳＫ带）,分布于同一井的３５７０～３３０１．５ｍ井段,孢粉丰度较下组合高得多,具环孢子含量一般在５０％以上,花粉含量增高。地质时代属晚石炭世早期（纳缪尔Ｂ—Ｃ期）。     

浙江桐庐冷坞二叠纪生物礁的发育模式

礁体底部具脉状层理的潮坪相碎屑沉积,礁体内部藻叠层岩夹层的存在,及礁体上部为煤系地层覆盖等都表明冷坞生物礁是一个典型的二叠纪岸礁;海绵骨架岩的存在表明它是个骨架型岸礁。     

Late Permian to Late Triassic palaeomagnetic data from Iran: constraints on the migration of the Iranian block through the Tethyan Ocean and initial destruction of Pangaea

A palaeomagnetic study of Late Permian to early Jurassic rocks from the Alborz and Sanandaj–Sirjan zones in Iran and a compilation of selected palaeopoles from the Carboniferous to the present provide an updated history of the motion of the Iranian block within the Tethys Ocean. The Iran assemblage, part of Gondwana during the Palaeozoic, rifted away by the end of the Permian. We ascertain the southern-hemisphere palaeoposition of Iran at that time using magnetostratigraphy and show that it was situated close to Arabia, near to its relative position today. A northward transit of this block during the Triassic is shown, with an estimated expansion rate of the Neotethyan ridge of 100–140  km Myr⁻¹. The northward convergence with respect to Eurasia ended during the Ladinian (Middle Triassic), and is marked by a collision in the northern hemisphere with the Turan platform, which was the southern margin of the Eurasian continent at that time. No north–south component of shortening is evidenced north of Iran afterwards. An analysis of the declinations from the Late Permian to the present shows different, large rotations, emphasizing the important tectonic phases suffered since the Triassic. Finally, we propose palaeomagnetic reconstructions of the Tethys area during the Late Permian and the Late Triassic, showing that the Palaeotethys Ocean was narrower than previously thought, and did not widen its gate to the Panthalassa before the Triassic period.     

甘肃玉门鱼儿红盆地石炭二叠纪地层概述——兼论北祁连山一带华夏-安加拉混生植物群的地质时代

概述玉门鱼儿红盆地煤窑沟和金沟石炭二叠纪地层剖面，指出该区石炭纪岩石地层单元为羊虎沟组，二叠纪岩石地层单元为窑沟群，区内缺失大黄沟组。根据生物化石和地层层序，讨论了羊虎沟组和窑沟群的地质时代。Ｂｏｈｌｉｎ（１９７１）公布的少许有疑问的安加拉植物分子可能采自邻区的上二叠统上部。     

山西大同煤田晚石炭世晚期和早二叠世早期植物群

对山西大同煤田晚石炭世晚期和早二叠世早期植物化石进行了研究，共鉴定植物化石２１属４８种，划分２个植物组合，讨论了植物群的特征和时代；此外，还论证了本区晚石炭世晚期和早二叠世早期植物群指示的古气候条件