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51.
52.
塔里木盆地塔中Ⅰ号带西北部上奥陶统碳酸盐岩同生期岩溶——以顺2井为例 总被引:5,自引:1,他引:4
在对塔中Ⅰ构造带西北部的顺2井奥陶系碳酸盐岩详细岩心观察和室内研究基础上,通过对岩溶作用中的泥质和方解石充填物的矿物组成、粘土成分、常量与微量元素和碳氧同位素的综合研究认为:顺2井良里塔格组碳酸盐岩取心井段显示出小型的潜流-缓流带及渗潜带岩溶结构,发育厚度为几十米(20~60m);具有块(粒)状结构、不发光泥微晶颗粒和裂隙充填方解石等大气水成岩特征及等粒镶嵌状结构、环带结构等埋藏或混合成岩作用特征;泥质充填物含稳定石英、钾长石、斜长石及代表埋藏早期未压实的标型矿物菱铁矿,相对高的CaO、K2O、Sr/Ba、B、F和相对低的Sr具负铈异常等;泥岩充填物中碳酸盐岩δ13C>0,中低负值的δ18O和Z>120;反映其形成于海相或处于海水-淡水混合带,代表了与沉积间断面有关的同生期表生岩溶的特征,后经历了成岩埋藏阶段的热液(水)作用改造。 相似文献
53.
Various fracture filling minerals and secondary minerals in fracture walls were formed by fluid-rock interaction during the exhumation of the Palaeogene Shimanto Belt of Kyushu, Japan, which is located in an accretionary complex. Each mineral formed under favourable geological conditions and can be used to estimate the conditions of accretion and formation of the related rock sequences. Petrographic observations, mineralogical and geochemical analyses were made on fracture filling minerals and secondary minerals from boreholes of ca. 140 m depth, drilled in the Shimanto Belt. Results reveal that the secondary minerals were formed in three major stages distinguished by the sequential textural relationships of the minerals and the interpreted environment of mineral formation. Filling mineral assemblages show that the studied rock formation has been subducted to a depth of several km and the temperature reached was ca. 200–300 °C. After the subduction, the rock formation was uplifted and surface acidic water penetrated up to 80 m beneath the present ground surface. The acid water dissolved calcite fracture filling minerals to form the present groundwater flow-paths, which allowed recent wall rock alteration to occur. The results shown here imply that filling mineral assemblages can be an effective tool to evaluate the environmental changes during exhumation of an accretionary complex. 相似文献
54.
Laura Valentini Bruno Capaccioni Piermaria Luigi Rossi Roberto Scandone Damiano Sarocchi 《Bulletin of Volcanology》2008,70(9):1087-1101
In order to provide new information about the source area and depositional mechanisms of the Upper Member of the Neapolitan
Yellow Tuff (NYT), a prominent pyroclastic deposit of the Campi Flegrei Volcanic District (southern Italy), statistics on
directional fabric, by means of computer-assisted image analysis on 32 rock samples, were compiled. Seventeen samples were
collected along vertical direction on two selected exposures and fifteen were taken from outcrops widely distributed all around
the Campi Flegrei Volcanic District. Fabric measurements within the investigated successions reveal a vertically homogeneous
direction of the mean particle iso-orientation, with considerable variability in the strength of particle iso-orientation
even at cm-scale. The existence of particle iso-orientation can be related to continuous sedimentation from a concentrated
bedload region beneath suspension currents, producing massive or inversely graded beds by traction carpet sedimentation. The
considerable vertical variability in the strength of iso-orientation is the result of very unstable flow regimes, up to the
extreme condition of discrete depositional events, with a variable combination of traction carpet and/or direct suspension
sedimentation. The vertical homogeneity in the mean orientation values, found in the investigated sections, may derive from
the sequential deposition of laminae to thin beds, whose relatively flat upper surfaces were unable to significantly deflect
the depositional system of the following currents. According to the observed homogeneous mean particle orientation values
along the investigated vertical profiles, samples collected through areal distribution are considered representative of the
local paleo-flow directions of the whole deposit. The mean directions of the samples collected areally show two different
coherent patterns which point to the existence of two different source areas. The first, which includes all samples from the
northern outcrops, appears to converge in a narrow area about 2 km NE of the town of Pozzuoli, largely in coincidence with
the inferred area on the basis of the pumice fall distribution. The second, which includes samples from Capo Miseno and Posillipo
areas, points to the central part of the Pozzuoli Bay, about 4 km offshore the town of Pozzuoli. 相似文献
55.
曲靖茨营下第三系中-碱性凝灰岩在农业生产中的开发应用 总被引:1,自引:1,他引:0
曲靖市茨营乡茨营—蔡家冲一带分布着下第三系蔡家冲组的中—碱性凝灰岩 ,厚2 1— 2 4m ,分布面积 69 75× 10 4 m2 ,其含沸石 5 8% ,蒙脱石 10 68% ,ω (K2 O) =3 71% ,稀土总量ω (REO) =0 0 34 %。具吸附性、吸水性、膨胀性及阳离子交换性能 ,是一种新型的农用岩石。储量 3141× 10 4 t。笔者对其理化性质进行了详细研究 ,为该凝灰岩改土肥田的机制提供了理论依据 ,又通过对该凝灰岩的可利用的元素激活、释放原理及化工工艺的研究 ,开发形成了系列的该凝灰岩为载体的复混 (合 )肥。在烟草、蚕桑、土豆、水稻、玉米五种作物多组试验、示范 ,证明系列凝灰岩复合肥肥效优于同营养成分的其他肥料 相似文献
56.
Over the past decade, land development activities on hillsides in northern Utah have resulted in a significant increase in
landslide activity throughout the region. The majority of recent landslides are shallow and they occurred on cut gentle slopes
especially during spring and early summer due to snowmelt induced elevated groundwater tables. The geologic material documented
at numerous landslide sites is a soft gray-green completely decomposed Norwood Tuff. The present study addresses the mechanism
of a shallow landslide in completely decomposed Norwood Tuff based on field, laboratory and numerical investigations. Detailed
slope surface geometry obtained from laser-scan surveys together with strength and stress–strain parameters derived from laboratory
triaxial tests on undisturbed samples of completely decomposed Norwood Tuff collected from the landslide site are employed
with finite-element modeling to examine the effects of ground surface deformation patterns on the yielding behavior of the
slide mass. The numerical results indicate a gradual retreat of the yield zone with progressive landslide deformation, which
eventually becomes concentrated within the accumulation zone of the landslide, compared to a well-developed yield zone within
the entire slide mass at the onset of landslide movement. Limit equilibrium stability analyses along potential sliding surfaces
of extent limited within the yield zone of the displaced slide mass produce lower safety factors than an analysis based on
the original sliding surface comprising the entire slide mass. 相似文献
57.
新疆西准噶尔包古图组凝灰岩锆石SHRIMP年龄及其地质意义 总被引:27,自引:12,他引:15
西准噶尔地区出露巨厚层的下石炭统火山-沉积岩,包括太勒古拉组、包古图组和希贝库拉斯组,前人主要通过生物化石来确定各组之间的层位关系,并存在争论。本文对包古图金矿区包古图组中3个蚀变凝灰岩样品开展的锆石SHRIMP年代学研究表明,凝灰岩的年龄分别为328.4Ma(MSWD=0.72)、342.6Ma(MSWD=0.76)和336.5Ma(MSWD=1.6)。结合太勒古拉组年代学数据和下石炭统火山-沉积地层的分布关系,确定西准噶尔下石炭统火山-沉积地层从下到上依次为:希贝库拉斯组、包古图组和太勒古拉组。 相似文献
58.
西藏谢通门县雄村地区洞嘎金矿作为南拉萨地体较早发现的独立金矿,其成矿作用研究较为薄弱。本文以洞嘎金矿赋矿凝灰岩为研究对象,开展了岩相学、年代学、地球化学和Hf同位素特征研究,探讨洞嘎金矿赋矿凝灰岩的岩石成因及构造背景,揭示凝灰岩对成矿的控制作用。LA- ICP- MS锆石U- Pb定年结果显示,凝灰岩结晶年龄为185. 1 ± 1. 9 Ma(MSWD = 0. 48),成岩时代为早侏罗世;主量元素地球化学特征显示K2O/Na2O值(2. 91 ~ 12. 3)较高,属于钙碱性系列;微量元素地球化学特征显示富集大离子亲石元素(如Sr、Ba)和轻稀土元素(LREEs),亏损高场强元素(如Nb、Ta、Ti等)和重稀土元素(HREEs)。结合微量元素构造环境判别图解,认为凝灰岩形成于新特提斯洋洋壳北向俯冲相关的大洋岛弧环境。另外,凝灰岩以Nb/Ta值为14. 0 ~ 17. 8、La/Nb平均值<2. 50、Zr/Ba平均值为0. 31为特征,具有较高的正的εHf(t)(+ 8. 05 ~ + 14. 2),暗示凝灰岩岩浆源区为受到新特提斯俯冲洋壳释放的流体交代的亏损软流圈地幔楔;岩浆上升侵位的过程中未受到地壳物质的混染,主要经历了橄榄石和单斜辉石结晶分异。洞嘎金矿赋矿凝灰岩中的裂隙构造不仅为洞嘎金矿的含矿热液运移提供了空间,而且也为矿质的沉淀提供了场所;同时,凝灰岩也起到了盖层作用,保护矿床形成后免受剥蚀作用的影响。综合分析认为,洞嘎金矿形成于新特提斯洋北向俯冲的大洋岛弧环境,是斑岩型铜金矿床外侧的热液脉型金矿体。 相似文献
59.
60.
江陵浅水-半深水坳陷湖盆层序地层学特征 总被引:2,自引:1,他引:2
以层序地层学理论为指导,系统研究了江陵浅水-半深水坳陷湖盆的层序地层学特征。研究表明:区域不整合界面和沉积转换界面是级层序的主要界面;层序内虽均发育低位、湖侵和高位体系域,但各体系域发育程度是不同的,致使层序的旋回性以非对称为主;层序内各体系域的沉积相构成均以河流三角洲和浅水湖泊为主,而冲积扇、扇三角洲不发育,湖泊水体基本没有发生过明显的扩张、收缩,湖平面的波动没有造成沉积相带的区域性变化,在此基础上,建立了江陵浅水-半深水坳陷湖盆特有的两种层序地层充填模式。 相似文献