全吉地块花岗片麻岩中镁铁质岩包体的矿物演化和锆石定年与古元古代区域变质作用

全吉地块中段古元古代早期的德令哈二长花岗片麻岩中发育一个来自围岩的变质镁铁质岩包体。该包体的岩性从核部到边缘依次为角闪斜长辉石岩、斜长角闪岩和石榴石角闪片岩。角闪斜长辉石岩的显微结构指示三个世代的矿物演化,世代Ⅰ为单斜辉石+棕绿色普通角闪石+斜长石+石英+钛铁矿,世代Ⅱ为蓝绿色普通角闪石+斜长石+石榴子石,世代Ⅲ为阳起石+钠长石+黝帘石。世代Ⅰ指示其峰期变质达高角闪岩相条件。角闪斜长辉石岩的锆石全部为浑圆状多晶面晶体,其CL图像具高温变质结晶特征。LA ICPMS技术测定获得上交点U Pb年龄为（1 913±38） Ma（MSWD=015）,指示峰期变质发生在古元古代末。研究表明,全吉地块中区域性分布的古元古代早期的二长花岗片麻岩与达肯大坂岩群在响应全球Columbia超大陆汇聚事件中一起发生了区域变质作用。     

阜平片麻岩之成因

阜平片麻岩的主体成分为灰片麻岩,其稀土型式相似于世界各地的太古代灰片麻岩。该灰片麻岩含丰富的变基性岩包体,二者构成双峰式系列,并经历了强烈形变,变质级别达高角闪岩相。阜平灰片麻岩由基性来源部分熔融而形成。     

南秦岭佛坪地区五龙花岗质岩体的地球化学特征及成因研究

南秦岭印支期五龙岩体侵位于中元古代佛坪群变质岩,在岩体南部发育一些暗色包体.它们和寄主黑云母花岗闪长岩界限或截然,或呈过渡关系.通过对五龙岩体的地球化学、锆石LA-ICP-MS U-Pb年代学研究结果表明,寄主黑云母花岗闪长岩表现出明显埃达克岩的地球化学特征:强烈亏损重稀土元素Yb(0.33×10-6～0.96×10-6)和Y(4.77×10-6～11.2×10-6);富集Sr(643×10-6～1115×10-6),Ba(775×10-6～1386×10-6);高Sr/Y(57.8-160)和Y/Yb(11.0-14.3)比值,不发育Eu异常(δEu=0.70～0.83),表明其源区是以石榴石士角闪石为主,很少或没有斜长石.暗色包体表现出高Mg(4.15%～8.13%),Cr(14.8×10-6～371×10-6),Ni(20.0×10-6～224×10-6)和Nb/Ta(15.40～21.9),暗示其起源于地幔底侵岩浆.锆石LA-ICP-MS U-Pb定年年龄为:225.3Ma±6 Ma,应为五龙黑云母花岗闪长岩的侵位年龄.综合分析五龙埃迭克质黑云母花岗闪长岩可能是由于幔源岩浆底侵于壳幔边界,诱发增厚的基性下地壳达到含角闪石的榴辉岩相或麻粒岩相发生部分熔融形成埃迭克质岩浆,它的形成可能代表了印支期秦岭造山带后碰撞造山阶段勉略洋俯冲板块的断离作用.     

Geochemical Characteristics and Metallogenesis of the Qingkuangshan Ni‐Cu‐PGE Mineralized Mafic‐Ultramafic Intrusion in Huili County,Sichuan Province,SW China

The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe region of Huili County, Sichuan Province, is one of several Ni-Cu-PGE deposits in the Emeishan Large Igneous Province (ELIP). The ore-bearing intrusion is a mafic-ultramafic body. This paper reports major elements, trace elements and platinum-group elements in different types of rocks and sulfide-mineralized samples in the intrusion. These data are used to evaluate the source mantle characteristics, the degree of mantle partial melting, the composition of parental magma and the ore-forming processes. The results show that Qingkuangshan intrusion is part of the ELIP. The rocks have trace element ratios similar to the coeval Emeishan basalts. The primitive mantle-normalized patterns of Ni-Cu-PGE have positive slopes, and the ratios of Pd/Ir are lower than 22. The PGE compositions of sulfide ores and associated rocks are characterized by Ru depletion. The PGE contents in bulk sulfides are slightly depleted relative to Ni and Cu, which is similar to the Yangliuping Ni-Cu-PGE deposit. The composition of the parental magma for the intrusion is estimated to contain about 14.65 wt% MgO, 48.66 wt% SiO2 and 15.48 wt% FeOt, and the degree of mantle partial melting is estimated to be about 20%. In comparison with other typical Ni-Cu-PGE deposits in the ELIP, the Qingkuangshan Ni-Cu-PGE deposit has lower PGE contents than the Jinbaoshan PGE deposit, but has higher PGE contents than the Limahe and Baimazhai Ni-Cu deposit, and has similar PGE contents to the Yangliuping Ni-Cu-PGE deposit. The moderate PGE depletions in the bulk sulfide of the Qingkuanghan deposit suggest that the parental magma of the host intrusion may have undergone minor sulfide segregation at depth. The mixing calculations suggests that an average of 10% crustal contamination in the magma, which may have been the main cause of sulfide saturation in the magma. We propose that sulfide segregation from a moderately PGE depleted magma took place prior to magma emplacement at Qingkuangshan, that small amounts of immiscible sulfide droplets and olivine and chromite crystals were suspended in the ascending magma, and that the suspended materials settled down when the magma passed trough the Qingkuangshan conduit. The Qingkuangshan sulfide-bearing intrusion is interpreted to a feeder of Emeishan flood basalts in the region.     

Geochronology of the Gabbro–mafic Microgranular Enclaves–granite Associations in the Gejiu District, Yunnan Province and Their Geodynamic Significance

Many igneous rocks distribute in Gejiu tin polymetallic ore-field at Yunnan province, rocks including basalt, gabbro, mafic microgranular enclaves, granites (porphyritic granite and equigranular granite) and akaline rocks. The ages of the granites and akaline rocks which are considered to have genetic connecting with the mineralization have been comfirmed, but the gabbro-mafic microgranular enclaves-granite assemblage’s ages are still unknown. By means of LA-ICP-MS zircon U-Pb dating, the data of Shenxianshui equigranular granite, the mafic microgranular enclave in Jiasha area, the host rock of the mafic microgranular enclaves and the Jiasha gabbro are around ~80 Ma. Besides the above mentioned data, a group of new ages at ~30 Ma were discovered in this study, which is from gabbro and mafic microgranular enclaves. Based on the previous data and the new data gained this time, we suggest the major geochronology framework of the magmatism and mineralization events in Gejiu area is ~80 Ma, which is consistent with the Late Cretaceous magmatism and mineralization events in the whole southeast Yunnan and west Guangxi area and they were suggested to belong to the same geotectonic setting in late Yenshannian. And the new ages of the ~30 Ma obtained in this study is considered to represent a responding to the complicate tectonic evolution history of the Tibetan orogenic events in Cenozoic.     

中国东部典型铁镁质尾矿的潜在固碳能力评估

      利用铁镁质尾矿与CO2 反应,形成稳定的碳酸盐矿物,是一种新型的、有前途的固定二氧化碳方法,而对于这些尾 矿固碳潜力的评价则是正确利用尾矿的前提。该文通过我国东部两个典型超基性岩带（东海-日照岩带和赤城-朝阳岩带） 10 个矿床尾矿的矿物组分、粒度分布以及相关元素的测定分析,评估不同矿床尾矿的潜在固碳能力。分析结果显示 ：在东海- 日照岩带,尾矿中MgO 的含量较高（36.81%~41.39%）,且多以蛇纹石为主,粗粒物质相对较多;而在赤城-朝阳岩带,尾 矿中MgO 含量中等（5.84%~15.60%）,而CaO 含量偏高（5.68%~19.28%）,矿物组分以各种角闪石为主,尾矿颗粒较细。结 合野外调研和计算,估计赤城-朝阳岩带可以用于封存CO2 的尾矿潜力为4.0×108 t,远远高于东海-日照岩带。综合化学 成分、比表面积、尾矿储量等各方面因素,赤城-朝阳超基性岩带具有很大CO2 封存潜力     

砂岩侵入复合体的建筑结构要素及其特征

砂岩侵入复合体是指沉积砂质母岩,在未固结时由于某种机制而积累了异常高压,产生液化、流化、再活动,向上覆细粒沉积物侵入的各种砂体的总和。目前已经在全球50多个深水盆地中(Braccinietal,2008)及所有的年代地层中都发现了从毫米到千米级别的砂岩侵入体。砂岩侵入复合体包含母岩、侵入体系和喷出体系三部分,通过对目前报道的一些砂岩侵入复合体实例分析,对其各建筑要素的外部几何形体和边界特征、内部沉积构造和显微结构进行了总结。不规则的几何形态,突变的边界特征,与液化作用相关的无构造砂岩、碟状构造、管状构造以及独特的泥岩碎屑表现出来的粒序性、条带等沉积构造,形状各异的矿物颗粒以及泥岩碎屑中砂岩裂缝切割等显微结构都可以作为识别砂岩侵入复合体的标准。加强砂岩侵入复合体的研究,为侵入圈闭的勘探和开发提供理论基础。     

松辽盆地安达地区营城组中基性火山岩成藏主控因素

松辽盆地中基性火山岩主要发育于安达次洼陷地区,其产出的天然气量占研究区深层产能总量的60%左右。研究区中基性火山岩气藏以沙河子组暗色泥岩和煤层为烃源岩,营城组三段粗面岩、玄武岩、中基性火山角砾岩等为储层,登娄库组二段泥岩为直接区域盖层,并发育多种岩性、构造圈闭,具备有利的成藏条件。利用地质资料和物性数据分析有效储层特征,结合测井综合解释和试气结果分析了气藏在剖面和平面上的分布特点,研究了安达次洼陷地区营城组中基性火山岩成藏主控因素。结果表明：岩性和岩相影响有效储层的发育,喷溢相粗面岩和玄武岩是该区主要的有效储层类型,爆发相中基性火山角砾岩储层物性最好,今后勘探中应予以重视;火山旋回控制气藏的纵向分布,即气藏主要位于各个火山旋回/期次顶部和上部;火山机构相带控制气藏的平面分布,气藏主要分布于火山口-近火山口相带。     

Petrology, geochemistry and tectonic settings of the mafic dikes and sills associated with the evolution of the Proterozoic Cuddapah Basin of south India

In this article we summarize the petrological, geochemical and tectonic processes involved in the evolution of the Proterozoic intracratonic Cuddapah basin. We use new and available ages of Cuddapah igneous rocks, together with field, stratigraphic, geophysical and other criteria, to arrive at a plausible model for the timing of these processes during basin evolution. We present petrological and geochronological evidence of dike emplacement along preferred lineament directions around the basin in response to stresses, which may have been responsible for the evolution of the basin itself. Basaltic dike intrusion started on the south Indian shield around 2400 Ma and continued throughout the Cuddapah basin evolution and sedimentation. A deep mantle perturbation, currently manifested by a lopolithic cupola-like intrusion under the southwestern part of the basin, may have occurred at the onset of basin evolution and played an important role in its development. Paleomagnetic, gravity and geochronological evidence indicates that it was a constant thermal source responsible for dike and sill emplacement between 1500 and 1200 Ma both inside and out-side the basin. Lineament reactivation in the NW-SE and NE-SW directions, in response to the mantle perturbation, intensified between 1400 and 1200 Ma, leading to the emplacement of several cross cutting dikes. Fe-Mg partition coefficients of olivine and augite and Ca-Na partition coefficient of plagioclase, calculated from the composition of these minerals and bulk composition of their host rocks, indicate that the dikes outside the Cuddapah basin are cumulates. The contemporary dikes may be related by fractional crystallization as indicated by a positive correlation between their plagioclase Ca# (atomic Ca/[Ca+Na]) and augite Mg# (atomic Mg/[Mg+Fe]). A few NW-SE and NE-SW cross cutting dikes of the period between 1400 and 1200 Ma, preserve petrographic evidence of episodic magmatic intrusive activity along preferred directions. Petrological reasoning indicates that a magmatic liquid reacted with a set of cross cutting dikes, intruding into one that was already solidified and altering the composition of the magma that produced the other dike. The Cuddapah basin tholeiites may be related by fractional crystallization at 5 kb and 1019-1154‡ C, which occurred in the lopolithic cupola near the southwestern margin of the basin. Xenolith bearing picrites, which occur near the periphery of the cupola, originated by the accumulation of xenoliths in the tholeiites. This is indicated by the composition of the olivine in the xenoliths (Fo_78.7-81.9), which are closely similar to calculated olivine compositions (Fo_77.8-78.3) in equilibrium with the tholeiites under the sameP-T conditions. It is inferred that fractionation in the cupola resulted in crystals settling on its walls. Hence, the xenolith-bearing sills occur at the periphery of the lopolithic body. The tholeiites both inside and outside the basin are enriched in incompatible elements compared to mid oceanic ridge basalts. The Ba, Rb and K contents of the Cuddapah and other Proterozoic Gondwana tholeiites indicate that a widespread metasomatic enrichment of the mantle source may have occurred between R∼2.9 and R∼2.7Ga. There may be local heterogeneity in the source of the Cuddapah tholeiites as indicated by different Ba/Rb, Ti/Zr, Ti/Y, Zr/Nb and Y/Nb in samples inside and outside the basin. Large-scale differences such as the low P₂O₅-TiO₂ and high P₂O₅-TiO₂ basaltic domains of the Jurassic Gondwana basalts, however, did not exist during the Proterozoic time period under consideration. Although we are beginning to understand the tectono-magmatic processes involved in the evolution of the Cuddapah basin, much work remains to be done to obtain a complete picture. Future research in the Cuddapah basin should focus on obtaining accurate ages of the igneous rocks associated with the evolution of the basin.