喀什凹陷中生代以来的构造事件对中-下侏罗统铀矿化的影响

喀什凹陷是我国西部重要的含铀区,自中生代以来主要发生过5次重大构造事件,对该地区中-下侏罗统铀矿成矿及保矿具有重要意义,即晚三叠世有利的构造背景,早-中侏罗世有利的构造-沉积环境形成的有利岩性-岩相建造,晚侏罗世构造掀斜与古层间氧化带及铀矿化的形成,白垩纪-古近纪的保矿作用及新近纪以来的构造破坏与局部层间氧化带的形成与叠加,从而很可能在中-下侏罗统中形成一定规模受层间氧化带控制的砂岩型铀矿床。指出主要找矿靶区为库孜贡苏断陷以西的南天山山前,同时还有托云盆地。     

REE Abundance and REE Minerals in Granitic Rocks in the Nanling Range,Jiangxi Province,Southern China,and Generation of the REE‐rich Weathered Crust Deposits

Studies of Mesozoic granites associated with rare earth element (REE)‐rich weathered crust deposits in southernmost Jiangxi Province indicate that they have high‐K to shoshonite compositions and belong to ilmenite‐series I‐type granites. Of the studied rocks at 59–292 ppm of bulk REE content, the highest are seen in the biotite granites of Dingnan (358, 429 ppm) and mafic biotite granite of the Wuliting Granite (344 ppm) near the Dajishan tungsten mine, both areas where weathered‐crust REE deposits occur. REE‐bearing accessory minerals in these granites are mainly zircon, apatite and allanite, and REE‐fluorocarbonates are common. REE enrichment occurs in the rims of apatite crystals, and in fluorocarbonates that occur along grain boundaries of and cracks in major silicate minerals, and in fluorocarbonates that replaced altered biotite. It is therefore thought that a major part of the REE content of these granites was concentrated during deuteric activity, rather than during magmatic crystallization. The crack‐filling REE‐fluorocarbonates could subsequently have been easily leached out and deposited in weathered crust developed during a long period of exposure.     

内蒙古西乌珠穆沁旗地区寿山沟组烃源岩 有机地球化学特征

内蒙古西乌珠穆沁旗地区广泛出露下二叠统寿山沟组暗色泥页岩.选取该组塔宾庙林场剖面的烃源岩样品,进行有机质丰度、类型、成熟度等有机地球化学特征研究,初步对其生烃潜力进行评价.研究表明,西乌旗地区下二叠统寿山沟组暗色泥页岩的有机质丰度达到了中等—好烃源岩标准;有机质来源以高等植物为主,干酪根类型以Ⅲ型为主.有机质热演化进入高成熟—过成熟演化阶段,是潜在的烃(特别是气)源岩,系上古生界重要的烃源岩勘探层系之一.     

Comparative phylogeography of African rain forest trees: A review of genetic signatures of vegetation history in the Guineo-Congolian region

The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study.     

闽西-赣南早-中侏罗世盆地及其火成岩特征

闽西-赣南地区早、中侏罗世陆相盆地带东起福建永定,经江西寻乌到龙南,断续延伸约250km,宽60～80km.受后期构造破坏和花岗岩浆侵入影响,现呈肢解散碎的残留盆地面貌.盆地边界特征和盆区岩层节理测量统计结果反映该区自晚三叠世以来,先后经历了近S-N向水平挤压(T3-J1E),S-N向垂向挤压、近E-W向水平伸展(J1L-J2),SE-NW向挤压(K1)和近E-W向挤压、S-N向伸展(K2)等复杂的演化过程.早-中侏罗世强烈的拉张-断陷作用导致盆区大量双峰式火山岩的喷发,其基性端员玄武岩的颗粒锆石U-Pb年龄值为170±1Ma,酸性端员流纹岩Rb-Sr等时线年龄为179Ma～165±2Ma.流纹岩具有高的SiO2、Al2O3、K2O含量,ANKC值＞1.1;轻稀土富集、稀土总量高,铕亏损,具明显Eu负异常;富集Rb、Th,贫化Ba、Ti、P、Nb、Zr等特点,属富钾过铝火山岩类.与之共生的玄武岩则以富硅贫碱为特征,轻稀土轻度富集,铕异常不明显;弱富集Rb、Ba、Th、Ce,贫Nb、Zr、Y,配分样式呈上凸型,属拉斑系列玄武岩类,反映一种后造山的陆内裂谷环境.闽西-赣南地区盆山格局的形成经历过多期地球动力学演化前中生代近E-W向古亚洲构造域的基底阶段,晚三叠世-早侏罗世早期挤压造山阶段,早侏罗世晚期-中侏罗世裂谷盆地阶段,早白垩世太平洋构造域对本区的置换和改造阶段,包括早期的火山-岩浆活动和晚期的伸展断陷盆地作用.     

Tectonic controls on metamorphism, partial melting, and intrusion: timing and duration of regional metamorphism and magmatism in the Ni de Massif, Turkey

Mafic high-pressure granulite, eclogite and pyroxenite xenoliths have been collected from a Mesozoic volcaniclastic diatreme in Xinyang, near south margin of the Sino-Korean Craton (SKC). The high-pressure granulite xenoliths are mainly composed of fine-grained granoblasts of Grt+Cpx+Pl+Hbl±Kfs±Q±Ilm with relict porphyritic mineral assemblage of Grt+Cpx±Pl±Rt. P–T estimation indicates that the granoblastic assemblage crystallized at 765–890 °C and 1.25–1.59 GPa, corresponding to crustal depths of ca. 41–52 km with a geotherm of 75–80 mW/m². Calculated seismic velocities (V_p) of high-pressure granulites range from 7.04 to 7.56 km/s and densities (D) from 3.05 to 3.30 g/cm³. These high-pressure granulite xenoliths have different petrographic and geochemical features from the Archean mafic granulites. Elevated geotherm and petrographic evidence imply that the lithosphere of this craton was thermally disturbed in the Mesozoic prior to eruption of the host diatreme. These samples have sub-alkaline basaltic compositions, equivalent to olivine– and quartz–tholeiite. REE patterns are flat to variably LREE-enriched (La_N/Yb_N=0.98–9.47) without Eu anomaly (Eu/Eu*=0.95–1.11). They possess 48–127 ppm Ni and 2–20 ppm Nb with Nb/U and La/Nb ratios of 13–54 and 0.93–4.75, respectively, suggesting that these high-pressure granulites may be products of mantle-derived magma underplated and contaminated at the base of the lower crust. This study also implies that up to 10 km Mesozoic lowermost crust was delaminated prior to eruption of the Cenozoic basalts on the craton.     

中国南方下寒武统黑色岩系及其地质研究意义

黑色岩系是C、N、P、S、O和一些重金属的循环链,既是一种矿产资源,又是环境因素的良好载体.以我国南方下寒武统为例,讨论黑色岩系的地质研究意义,提出黑色岩系的重点研究方向.     

鄂尔多斯盆地北部塔巴庙地区下石盒子组盒3段储层特征及有利区块预测

根据野外剖面、钻井岩芯和测井等资料,系统地对塔巴庙地区下石盒子组盒3段储集砂体的岩石学特征、孔隙类型、成岩作用以及物性进行了详细的分析。研究表明,储集层的成分和结构成熟度低;主要孔隙类型有粒间孔、粒内溶孔、晶间溶孔、铸模孔和粒缘缝;孔隙度为0.7%~18.69%,平均值为7.82%;渗透率为0.008×10^-3μm²~23.01×10^-3μm²,平均值为1.111×10^-3μm²,属于物性中-偏低的微孔-溶孔型组合型储集岩。影响储集层的主控因素包括:(1)河道控制了优质储层的分布范围和规模;(2)成岩期早期环边绿泥石胶结、溶蚀等建设性成岩作用是形成储层的基础;(3)成岩相扩大了储层的分布范围,改善了储层的物性。在上述研究的基础上,结合储集砂体的沉积微相特征、物性平面展布特征、储集砂体成岩相特征,在研究区内圈定了Ⅱ、Ⅲ两类有利勘探区块,为研究区下一步的勘探、开发提供了科学依据。     

济阳坳陷桩海地区下古生界硅化岩溶储集层空间分布模式

基于岩心描述和镜下观察,分析了研究区下古生界硅化岩溶储集层的岩性特征。通过对沟通潜山 断块和古近纪洼陷的边界断层产状、潜山断块内下古生界产状的分析,认为下古生界碳酸盐岩具备埋藏岩溶作 用条件,提出了古近纪沉积物压释酸性水向潜山断块运移的3种方式,即：翘倾端断面补给畅流运移模式、倾 没端断面补给畅流运移模式和背斜凸起两侧双向渗入补给对流循环模式。利用这 3种模式可以合理解释研究区 下古生界潜山硅化岩溶储集层空间分布的特点和规律。翘倾端断面补给畅流运移模式可以解释潜山断块高部位 硅化岩溶层段储集层的发育情况,倾没端断面补给畅流运移模式和背斜凸起两侧纵向渗入补给对流循环模式, 可以解释潜山断块的低部位硅化岩溶层段储集层的发育情况。该模式还可以合理地解释硅化岩溶储集层在下古 生界赋存层位的 “ 穿层性”特点,同时也能够合理解释潜山断块周缘发育硅化岩溶层段,而潜山断块中心地带 很少出现硅化岩溶层段等现象。