Three–Dimensional Isotopic Characteristics of Crystalline Limestone around the Sakonishi Zn Ore Bodies in the Kamioka Mining District, Japan     

Yuichi MORISHITA 《Resource Geology》1999,49(4):243-257

Abstract: Predominant Zn-rich ore bodies were found to a deep part of the Sakonishi area in the Kamioka mining district, Japan. The ore mineralization was recognized at 230 to 300m above sea level in the Sakonishi area. Since crystalline limestone is broadly distributed over the area, and the variation in isotopic composition is easily detected, the isotopic prospecting should be powerful in surveying of the extent of the ore bodies and the related hydrothermal system. Although isotopic anomalies have been extracted two-dimensionally so far, three-dimensional information is possibly more powerful. In this paper, Zn-rich ore bodies in the Sakonishi area are treated as hydrothermal ore deposits, and the importance of the activity of hydrothermal fluids during mineralization is emphasized. Oxygen and carbon isotopic ‘iso–surfaces’ are three-dimensionally calculated for the Sakonishi area. The δ¹⁸O values of crystalline limestone from the surface and from the drill holes range from +8. 1 to +21. 1% and from –2. 7 to +20. 4%, respectively. The δ¹³C values of crystalline limestone from the surface and from the drill holes range from –1. 0 to +5. 3% and from –7. 7 to +4. 6%, respectively. The oxygen and carbon iso-topic ratios at the mineralization level are extremely low, but there are exceptions as to carbon isotopes. The oxygen isotopic ratios of crystalline limestone may decrease by isotopic exchange reaction with a hydrothermal fluid, while the carbon isotopic ratios slightly change. Since the precipitated calcite from a hydrothermal fluid has low carbon isotopic ratio and various oxygen isotopic ratio depending on the formation temperature, the bulk sample of crystalline limestone containing the precipitated calcite has oxygen and carbon isotopic ratios of relatively low values accordingly. Thus the decrease mechanism for carbon isotopic ratio of crystalline limestone is different from that for oxygen isotopic ratio. Samples with the carbon isotopic ratio of –4 to –8% are considered to be crystallized from hydrothermal fluids. Since the oxygen and carbon isotopic ratios of crystalline limestone at the ore mineralization level are low, the ore bodies are considered to have formed by a prominent hydrothermal activity. Thus oxygen and carbon isotopic ratios of crystalline limestone can be used as an indicator of the related hydrothermal activity. The alteration such as chloritization is intense near fractures in the Sakonishi area, showing that the hydrothermal system is controlled by a fracture system. It is assumed that the decreased isotopic ratios indicate the high degree of reactivity with hydrothermal fluids, and the depleted zone in oxygen and carbon isotopes may correspond to the conduit of the hydrothermal fluids.  相似文献   

试论皖北奥陶纪豹皮灰岩的古岩溶成因   总被引：1，自引：0，他引：1  

李定龙  杨为民  程学丰  汪才会 《地质论评》1999,45(5):463-469

本文通过对安徽北部两个奥陶系剖面豹皮灰岩(俗称豹斑)的宏观、微观及地球化学特征研究,认为豹皮灰岩的形成与奥陶纪灰岩沉积过程中的古岩溶作用及其后生改造密切相关。其形成演化模式可概括为4个阶段:①碳酸盐岩沉积间断暴露地表发育裂隙;②各种裂隙淋滤溶蚀形成沉积岩溶洞穴体系;③海侵导致海相沉积物充填岩溶洞穴;④回流渗透或混合作用使充填物白云石化而形成“斑”。  相似文献   

相对海平面升降与中国南方二叠纪生物礁油气藏   总被引：7，自引：0，他引：7  

沈安江  陈子 《沉积学报》1999,17(3)

根据相对海平面升降速率与礁生长速率之间的关系,中国南方二叠纪生物礁可划分为三种类型∶退积礁、并进礁和进积礁。不同类型的礁有其特有的成岩、成藏模式。首先,相对海平面升降控制了礁储集体的非均质性,这种非均质性又控制着原油在礁体内的时空展布,搞清这种时空展布规律对礁油气藏勘探极为重要;其次,相对海平面升降控制着礁含油气系统要素的形成机理及空间配置关系,对礁的含油气系统进行分析可在钻前对礁的含油气潜力作出初步评价。不同类型的礁体群均具有各自不同的成因联系及时空迁移规律,分析这种成因联系及时空迁移规律使我们可以更加准确预测潜伏礁体。  相似文献   

典型韵律互层式灰岩与泥灰岩的地球化学特征对比   总被引：1，自引：0，他引：1  

黄文辉  W.M.Bausch 《沉积学报》1999,(4)

通过对德国南部地区上侏罗统麻姆组典型韵律互层式灰岩与泥灰岩进行逐层采样,并进行不溶残余物分析和地球化学测定对比,发现两者所含非碳酸盐物质没有区别。SiO2、Al2O3、Fe2O3、K2O和TiO2等来源于陆源碎屑物,在灰岩与泥灰岩中的比例完全相同,其含量的不同完全由碳酸盐物质的稀释所引起。元素Sr、Zn、Mn和Mg归为成岩作用控制元素,最先存在形式与碳酸盐有关,但成岩阶段变化极大,Mg的含量主要受白云岩化作用程度控制。另一组元素如S、Ba、Rb和P等介于以上两组元素之间,表现为部分受陆源碎屑物含量控制,部分受成岩作用影响。研究表明,灰岩与泥灰岩韵律互层形成的原因主要是由于碳酸盐物质的沉积速率变化所致,成岩阶段的压溶作用加大了两者的差异,但这种差异只表现在于碳酸盐物质与酸不溶残余物的比例上,而地球化学组成没有本质区别。  相似文献   

水下近建筑物的炸礁实践     

肖飞  范先力 《海岸工程》1999,18(3):39-41

介绍了前湾港一期工程杂货码头港池炸礁情况,证实了水大型码头在主体工程完成后,进行港池内礁岩爆破作业作可行性和必须采取的技术措施。  相似文献   

东昆仑南坡早二叠世灰岩块体的来源与成因探讨     

王永标  徐桂荣  林启祥  龚淑云 《地质科技情报》2000,19(4):35-39

论述了对东昆仑南坡早二叠世灰岩块体的成因的新认识。（１）在前人所称的三叠纪地层中发现了中薄层生物或生物碎屑灰岩,其中产有大量保存完好的早二叠苞类化石,所以该区早二叠世灰岩块体与其周围砂板岩及中薄层灰岩之间应属于同期上沉积。（２）该区早二叠世礁灰岩之下常伴生有砾岩及乐岩,而非礁相灰岩周转则常常缺乏砂砾岩,这种分布特征是礁上体系沉积的必然结果,但很难用推覆体来加以解释。（３）通过对砂砾岩与灰岩块体之间的地层序列研究,发现它们之间属于一种沉积接触关系,而非推覆体的关系,由于该地区早二叠世灰炭块体的成因对于该区大地构造的解释至关重要,因此这些新发发现将引起人们对该区大地构造的演化历史进行了重新思考。  相似文献   

西藏甲马弧内盆地甲马矿区晚侏罗世海绵礁的发现   总被引：1，自引：0，他引：1  

彭勇民  姚鹏  李金高 《地球学报》2000,21(3):328-333

西藏甲马弧内盆地晚侏罗世海绵礁属于台地边缘礁,呈近EW向展布,延伸长达4～5km,宽约50m,建筑在叶巴期火山岩浆弧的正地形上。由北向南展示出礁坪相到礁核相再到礁前斜坡相的侧向演变。其中礁核相主要由海绵骨架岩、障积岩和粘结岩等构成。海绵礁可分为并进礁和中止礁2种类型,发育至少6套垂向上相互迭叠的礁旋回。研究表明,甲马矿区海绵礁形成的关键因素是海平面变化,其主体的发育与海平面相对上升同步。  相似文献   

塔里木盆地奥陶系萤石脉—油气叠合成藏作用——高分辨率成像测井资料提供的证据   总被引：12，自引：0，他引：12  

钟广法  刘瑞林 《高校地质学报》2000,6(4):576-582

根据高分辨率电阻率成像测井解释,结 合岩心观察及薄片资料,探讨了塔里木盆 地塔中X井下奥陶统灰岩段内罕见的萤石脉—油气叠合成藏现象。萤石脉侵位于二叠纪塔里 木盆地中西部区域性火山活动时期,由上侵至地层浅部的低温岩浆热液沿断层、裂隙发育带 充填而成。萤石脉及其附近灰岩围岩中溶洞的形成为后期油气聚集提供了良好的储集条件, 它与充足的油气来源及上覆巨厚中、上奥陶统泥质岩有利的封盖条件配合,促成了油气在萤 石脉基础上的叠合成藏。该油气藏的发现为塔里木盆地油气勘探开辟了一个新领域,并丰富 了传统的油气成藏理论。  相似文献   

Early period of early Permian tubular cyanobacteria reef in the eastern part of south Qinling Mountains   总被引：1，自引：0，他引：1  

GONG Enpu  FAN Jiasong 《中国科学D辑(英文版)》2000,43(4):347-355

A typical reef occurs in the eastern part of south Qinling Mountains in Sanlixia, Xunyang, Shaanxi Province. The reef, extending in north-south direction, was built up by various kinds of calcareous tubes including Girvanella, tubular cyanobacteria and problem microbials. The bioclastic bank, built up by algal clasts, foraminiferous, and fusulinids, formed the reef basement, on which dasyclads baffle bioclasts formed the original bafflestone at a small scale on the reef basement, and then a mass of bindstone was made up by all kinds of calcareous tubes and algae. On lateral part the reef is cryptalgal mudstone. The reef that occurred in the geosynclinal area is so familiar with one of the platforms in many respects, such as in reef structure, morphology and building mold. This indicates that building organisms have amazing adaptability and identity for building capacity in the two kinds of geotectonic background mentioned above.  相似文献   

豫西鲁山洛峪口组宏观藻类的发现及地质意义   总被引：6，自引：1，他引：5  

尹崇玉  高林志 《地质学报》2000,74(4):339-343

本文报道在华北地台南缘豫西鲁山下汤九女洞剖面洛峪群洛峪口组下部灰绿色粉砂质页岩中发现可靠的宏观碳质印膜化石,包括Ｃｈｕａｒｉａ,Ｓｈｏｕｈｓｉｅｎｉａ,Ｔａｗｕｉａ,Ｏｖｉｄｉｓｃｉｎａ等属。通过同国内外已发现的前寒武纪宏观藻类资料广泛对比,并结合其他化石资料的综合分析,对华北地台南缘晚前寒武纪地层对比及新元古代地层格架进行探讨。  相似文献