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1.
天然气水合物沉积环境出现的岩石矿物主要为碳酸盐岩、黄铁矿、石膏等。自生碳酸盐岩的典型特点为极负的δ13CPDB值（最低可达-70．0‰）、正的δ18OPD。值（＋2．5‰-＋6．5‰），碳酸盐矿物主要为镁方解石、文石、白云石和菱铁矿。黄铁矿以霉球状、条状为主。石膏则主要为自形晶体，透明。此类自生岩石矿物与甲烷厌氧氧化过程或水合物的形成效应有关。南海沉积物中出现的自生碳酸盐岩、黄铁矿和石膏，其特点与水合物沉积环境中的十分类似，预示了南海可能存在有利于水合物成藏的地球化学过程。  相似文献   

2.
大陆边缘海的流体喷流活动或水合物分解都会导致自生碳酸盐岩的形成。南海北部神狐海区出现的自生碳酸盐岩主要为烟囱状，以铁白云石、文石、方解石碳酸盐矿物为主；稳定同位素研究显示，烟囱的δ^13CPDB值在-40．18‰～-38．69‰、δ^18OPDB值在3．75‰～4．31‰之间变化，显示了导源于甲烷厌氧氧化作用的特征，是海底富含甲烷的流体活动的最终产物。持续或间断的流体喷流活动，使神狐海区碳酸盐岩烟囱发生单阶段或多阶段沉淀。  相似文献   

3.
为了探索海洋天然气水合物背景下有孔虫特征的响应,对综合大洋钻探计划(IODP)311航次岩芯沉积物中底栖有孔虫Uvigerina peregrina和Bulimina mexicana进行了初步研究。通过对冷泉站位U1328和毗邻的非冷泉站位U1327沉积物中底栖有孔虫Uvigerina peregrina和Buliminamexicana的显微形貌特征和碳、氧稳定同位素测试等,证实有孔虫壳体未受到后期成岩作用的改造和自生碳酸盐岩的交代影响,有孔虫壳体的碳稳定同位素呈现明显的负偏。其中U1327站位中U.peregrinaδ13C为-0.67‰~-2.75‰(PDB),B.mexicanaδ13C为-0.51‰~-1.52‰(PDB);U1328站位中U.peregrinaδ13C为-0.72‰~-2.71‰(PDB),B.mexicanaδ13C为-0.58‰~-1.45‰(PDB)。底栖有孔虫壳体的碳稳定同位素负偏成因可能与水合物不稳定分解释放的甲烷厌氧氧化作用和食物源有关,因而可较好地指示海底天然气水合物系统地质背景。  相似文献   

4.
以青藏高原南羌塘坳陷扎仁地区中侏罗统布曲组晶粒白云岩为对象对其进行成因的研究。通过显微镜观察、流体包裹体数据以及碳氧同位素分析,认为研究区白云岩可分为细粉晶白云岩、中晶白云岩以及粗晶白云岩,在裂隙附近还广泛发育晶粒较粗大的鞍形白云石。白云石中流体包裹体均一温度在150.2～216.0℃,盐度均值达到了24.5%NaCl,远高于方解石包裹体均一温度与盐度,表明白云石的形成经历了高温高盐度的过程。白云石碳氧同位素分析显示其δ~(13)C_(PDB)值为-0.01‰～3.43‰,δ~(18)O_(PDB)值为-11.17‰～-7.68‰,通过白云石-水氧同位素分馏方程得到白云化流体的δ~(18)O_(SMOW)值为4.82‰～12.85‰,δ~(13)C_(PDB)对比认为白云石受寄主灰岩环境的影响。通过碳氧同位素数据对比以及前人的研究结果,认为研究区白云岩为相对封闭环境下受岩浆活动加热的高盐度流体对寄主灰岩交代的产物,高盐度流体由于镁离子的消耗导致流体对方解石过饱和,继而沉淀了高温的方解石。因此,热液活动对研究区中侏罗统布曲组白云岩的发育具有重要意义,值得加强对这一方向的探索研究。  相似文献   

5.
苏新  陈芳  陆红锋  黄永样 《现代地质》2008,22(3):376-381
对2002年"海洋四号"在南海北部深水冷泉活动区水深约3000m海底获得的1块自生碳酸盐岩展开了岩石学、地球化学和显微结构的分析研究。结果表明,该HD-83站位岩石样品为有多孔不规则块体,属于与扩散流有关的冷泉自生碳酸盐岩。其自生碳酸盐矿物成分为镁方解石或文石,含量达全岩的17%。全岩碳同位素值δ13C为-61.403‰,氧同位素值δ18O为3.5606‰,属于甲烷冷泉喷口成因自生碳酸盐岩,甲烷来源以微生物成因为主。该岩石显微结构有泡孔状、充填通道、不规则裂隙、虫孔边缘加厚4种主要类型。通过对比,推知这些显微结构可能与甲烷分解排气释放或流体逃逸通道有关。本研究注意到在岩石的裂隙或孔道中菌丝体普遍存在,可能属于菌席的组成份子,依靠通道内流体进行化能合成。  相似文献   

6.
塔深1井寒武系白云岩储层同位素流体地球化学示踪   总被引：3，自引：0，他引：3  
通过对塔里木盆地沙雅隆起阿克库勒凸起东部塔深1井寒武系白云岩岩石学特征及成岩成因分析,影响塔深1井寒武系地层流体改变主要成岩有准同生期、埋藏期和后期热液改造期等.塔深1井寒武系白云岩及充填孔、洞、缝内方解石的氧、碳、锶同位素地球化学特征表明:准生期白云岩δ~(13)C_(PDB)值(0.9‰～1.8‰)偏正、δ~(18)C_(PDB)值(-10.1‰～-4.2‰)偏负反映准同生期泥微晶白云石成因属于高盐度的海水使得碳酸盐泥发生白云石化;埋藏期白云岩碳、氧随重结晶作用加强,白云岩晶粒由细向粗变化值随埋深增加,由于同位素分馏作用而偏负,δ~(18)C_(PDB)值(-10.02‰～-5.7‰)呈明显的下降,但δ~(13)C_(PDB)值(-1.4‰～0‰)组成变化不大;后期热液白云岩在热液作用下δ~(18)C_(PDB)值普遍低于-10‰(δ~(18)C_(PDB)/‰-13.1～-9.4,δ~(13)C_(PDB)/‰-2～-0.647);基质方解石δ~(18)C_(PDB)值为-10.1‰～-10.13‰,δ~(13)C_(PDB)值为-1.48‰～-1.62‰;充填孔洞缝粗-巨晶方解石δ~(18)C_(PDB)值为-10.89‰～-14.28‰,δ~(13)C_(PDB)值为-2‰～-3.09‰,反映准同生期→埋藏期→后期热液晶粒大小由泥微晶→细晶→中晶→粗晶氧碳同位素值逐渐变小偏负,据~(87)Sr/~(86)Sr(0.707 284～0.746 888)值均远高于现今海洋中海水的锶同位素组成(0.708)及围岩的锶同位素(0.707 284),说明鞍形白云石以及方解石结晶时的孔隙流体不是残余在岩石孔隙中的同生期海水,而是外来的富含锶的流体,也就是深部热液流体.渗透回流白云石化、埋藏白云石化和高温热液白云石化等特征表明白云岩形成于超盐度、埋藏和高温热液等3种不同的环境,因此影响储层形成与分布,从而影响对白云岩的勘探.  相似文献   

7.
南海北部冷泉碳酸盐岩和石化微生物细菌及地质意义   总被引：23，自引：1，他引：22  
通过对2002年广州海洋地质调查局在南海北部海域拖网采集的碳酸盐岩样品进行岩石、矿物、微量元素和同位素特征的研究,证实在南海水合物远景区发育有冷泉碳酸盐岩。冷泉碳酸盐岩形态类似于烟囱,主要由方解石、伊利石、石英、黄铁矿和一种未知的矿物组成。保存了很可能是石化的甲烷氧化和硫酸盐还原细菌。碳酸盐岩矿物的δ^13CPDB为-51.24‰～-51．757‰。碳酸盐岩矿物的页岩标准化稀土元素配分模式具无Ce和Eu异常、微弱的轻稀土亏损和中稀土富集特征,表明形成于还原的缺氧环境,显示了冷泉碳酸盐岩的特征,指示在南海北部水合物远景分布区内冷泉活动的近海底可能发育有水合物。  相似文献   

8.
本文通过方解石和白云石的碳和氧同位素分析,对比研究了白云鄂博赋矿白云岩、黑脑包微晶丘、北京西山微晶丘、宽沟北正常沉积灰岩和白云鄂博碳酸岩墙,从而探讨了赋矿白云岩的成因及其与超大型Fe-Nb-REE矿床的成因关系。结果为:①黑脑包腮林忽洞群顶部微晶丘和北京西山寒武系顶部微晶丘碳酸盐的δ~(13)C值都在0±2‰左右,δ~(18)O值为18.3‰～25.1‰,均具有典型海相沉积碳酸盐岩的特点;②白云鄂博东矿采场δ~(13)C值为-7.9‰～-1.1‰,δ~(18)O值为9.1‰～20.9‰;矿区东西两端δ~(13)C值-7.9‰～-0.6‰,δ~(18)O值8.6‰～25.7‰;均介于地幔流体与典型沉积碳酸盐岩之间。部分赋矿白云岩样品中白云石与方解石之间的碳氧同位素分馏△~(13)C和△~(18)O值均小于0‰,表明其受到过次生蚀变作用,低δ~(18)O值白云石样品所对应的负△~(18)O值反映了地幔镁质流体对沉积碳酸盐岩的强烈交代作用;③矿区—富稀土碳酸岩墙的δ~(13)C值为-7.2‰～-4.7‰,δ~(18)O价值为11.9‰～16.4‰,表明其碳酸岩岩浆并非原始地幔来源,而可能与俯冲板块携带的沉积碳酸盐岩与地幔流体在深部的高温混合熔融有关。碳酸岩墙中白云石与方解石之间的碳和氧同位素分馏均小于0‰,说明该碳酸岩墙中的白云石与方解石并非同成因矿物,至少其中之一为  相似文献   

9.
为了探索水合物背景下沉积物中自生矿物响应,对采自综合大洋钻探计划（IODP）311航次沉积物中自生碳酸盐岩颗粒进行了矿物组成、形貌特征和碳、氧稳定同位素特征等研究。X光粉晶衍射（XRD）和扫描电镜（SEM）结果显示碳酸盐岩颗粒的主要矿物成分是铁白云石和方解石,呈多孔状结核和不规则状集合体产出。碳酸盐岩颗粒的碳稳定同位素δ13CPDB低至-41.50‰,证实其碳源源自甲烷,其成因与甲烷厌氧氧化过程有关,印证了研究区存在海底甲烷渗漏现象,是甲烷水合物赋存区重要的识别标志之一。碳酸盐岩颗粒的氧稳定同位素δ18OPDB总体上随着沉积物深度增加而减小,可能指示沉积物的背景温度由下而上（从早到晚）逐渐降低。研究结果提供了现代海洋天然气水合物背景下沉积物中自生碳酸盐岩的碳、氧稳定同位素记录,对于寻找我国海域天然气水合物资源,探索地史时期古海洋沉积物中类似的甲烷事件记录具有重要的理论和实践指导意义。  相似文献   

10.
显微取样碳氧同位素分析技术利用高聚焦激光束与碳酸盐岩样品作用,是一种在显微薄片下对岩石特定组构产生CO2的有效方法,其空间分辨率20～50μm,δ13C和δ18O的最好分析精度可达±0.22‰(σ),可以为碳酸盐岩碳氧同位素提供“高分辨率、原位”数据,微区分析是同位素测试发展的重要方向。用该技术对川东北飞仙关组鲕粒白云岩地球化学特征进行的研究表明,它可避免样品不纯带来的解释上的误差,为解释鲕粒白云岩成因提供了较为准确的地球化学信息,可进一步认识川东北飞仙关组鲕粒白云岩的成因问题。各种产状白云石的δ13C‰(PDB)值均大于当时海水值,说明白云石化流体没有淡水注入;而δ18O‰(PDB)分布较为离散,伴随白云石晶体大小增加,δ18O‰(PDB)值明显偏负,说明白云石化作用过程经历了埋藏加深、温度升高的过程,并且白云石化流体远离卤水源,其咸化程度减弱,为鲕粒白云岩的卤水渗透回流成因提供了有力的证据。  相似文献   

11.
The calcite fossils of the Derbyhaven Beds, Isle of Man, have δ13C values (+ 1·8 PDB) similar to modern, shallow-water marine skeletons, but the δ18O values (?6·1 PDB) are much lighter than modern skeletons. The light oxygen values indicate either re-equilibration with isotopically light water before cementation started, or Carboniferous sea water with δ18O of ?6‰. Aragonite dissolution was followed by precipitation of zoned calcite cement. In this cement, up to six intracrystalline zones, recognized in stained thin sections, show isotopic variation. Carbon varies from + 3-8 to + 1-2‰. and oxygen from ? 2-6 to ? 12-4‰. with decreasing age of the cement. This trend is attributed to increasing temperature and to isotopic evolution of the pore waters during burial. The zoned calcite is sequentially followed by dolomite and kaolinite cements which continue the trend towards light isotopic values. This trend is continued with younger, fault-controlled dolomite, and is terminated by vein-filling calcite and dolomite. The younger calcite, interpreted as a near-surface precipitate from meteoric waters, is unrelated to the older sequence of carbonates and has distinctly different carbon isotope ratios: δ13C ? 6-8‰.  相似文献   

12.
Recent (<50 years old) freshwater cyanobacterial carbonates from diverse environments (streams, lakes, waterfalls) throughout Britain and Ireland were analysed for their stable carbon and oxygen isotope compositions. The mean δ18O value of ?5–9‰ PDB for river and stream data represents calcite precipitation in equilibrium with the mean oxygen isotopic composition of precipitation in central Britain (?7–5‰SMOW) assuming a mean water temperature of 9°C. The mean δ18O of lake data, ?4–5‰ PDB, is statistically different, reflecting the effects of residence time and/or variations in the oxygen isotopic composition of rainfall. Carbon isotopes have wide variations in both fluviatile and lake data sets (+ 3 to ?12‰ PDB). These variations are principally controlled in the fluviatile samples by contribution of isotopically light ‘soil zone’ carbon relative to isotopically heavier carbon from limestone aquifer rock dissolution. Lake samples have the heaviest carbon isotope values, reflecting a trend toward isotopic equilibrium between atmospheric CO2 and aqueous HCO?3. We infer that isotopic compositions of ancient cyanobacterial carbonates should also record environmental information, although the effects of stabilization and diagenesis on primary δ18O values will need careful consideration. Primary carbon isotope compositions should be well preserved, although in marine samples values will be buffered by the isotopic composition of aqueous marine bicarbonate.  相似文献   

13.
通过成矿期方解石的C、O、Sr和含硫矿物的S、Pb同位素,成矿期方解石Sm-Nd测年研究,探讨白秧坪矿集区东矿带矿床成因。测试结果表明,白秧坪矿集区东矿带方解石δ13CPDB值变化范围-4.0‰~2.3‰,平均值-0.2‰,δ18OPDB值范围-27.2‰~20.4‰,平均值-14.1‰,δ18OSMOW值范围2.9‰~24.4‰,平均值16.4‰;方解石Sr同位素值变化范围0.707669~0.710115,平均值0.709320;硫化物δ34SV-CDT值分布范围-20.2‰~1.3‰,平均值约-8.8‰,天青石δ34SV-CDT值分布范围为17.1‰~19.4‰,平均值约18.0‰;Pb同位素测试结果中,206Pb/204Pb的变化范围为18.553~18.857,207Pb/204Pb变化范围为15.501~15.826,208Pb/204Pb变化范围为38.54~39.456;成矿阶段方解石Sm-Nd等时线年龄为29.5±1.7 Ma。对测试结果的研究表明,白秧坪矿集区东矿带碳质的来源较为均一,矿石中热液方解石碳质源自地层中碳酸盐岩溶解,成矿流体来自地层水和大气降水,属于盆地卤水流体系统;成矿物质硫来自海水硫酸盐的还原作用,成矿早期以有机质还原硫为主,成矿后期以生物还原硫为主;金属成矿物质来自沉积地层和盆地基底;测定白秧坪矿集区东矿带铅锌成矿年龄为29.5±1.7 Ma,与地质年龄限定的较为吻合。   相似文献   

14.
UWE BRAND 《Sedimentology》1982,29(1):139-147
The aragonitic molluscs and lime-mud of the Pennsylvanian Buckhorn asphalt (Deese Group) of southern Oklahoma precipitated calcium carbonate in oxygen and carbon isotopic equilibrium with ambient sea-water. In addition, δ18O values indicate that the pelecypods precipitated their shells during the warmer months of the year. The coiled nautiloids probably precipitated their shells in the warm surface water and throughout the year. For the orthocone nautiloids, the δ18O values suggest that they precipitated their shells in deeper/cooler water. The low-Mg calcite brachiopods of the Mississippian Lake Valley Formation of New Mexico precipitated shells in oxygen and carbon isotopic equilibrium with ambient sea-water. The δ18O and δ13C values of the Buckhorn and Lake Valley faunas, in conjunction with other published results, suggest that Carboniferous sea-water was, on a average, depleted in δ18O by 1·5 ± 2‰, PDB, relative to Recent sea-water. However, the δ13C value of +2.6 ± 2‰, PDB, for average Carboniferous sea-water is similar to that of Recent ocean water. Early diagenetic alteration of metastable carbonates probably occurs in a meteoric-sea-water mixing zone. In this zone the oxygen and carbon isotopic compositions of these components are increased by about 2-4‰, PDB over their marine composition.  相似文献   

15.
青河县哈腊苏铜矿床Ⅰ号矿化带位于准噶尔北缘卡拉先格尔斑岩铜矿带,铜矿化主要呈不均匀团块、细脉或细脉浸染状产于花岗闪长斑岩、石英闪长斑岩及玄武岩、辉斑玄武岩围岩中。矿石中石英和方解石流体包裹体划分为H_2O-NaCl型和H_2O-CO_2(±CH_4/N_2)-NaCl型。成矿温度主要集中在120～431℃,峰值在390、290和190℃。成矿流体盐度(w(NaCl_(eqv)))变化于0.53%～66.76%,峰值在19.5%、12.5%、9.5%和1.5%。密度为0.55～1.11 g/cm~3。矿脉中石英和方解石的δ~(18)O_(SMOW)值为2.9‰～12.3‰,δ~(18)O_(H_2O)值为—5.81‰～4.83‰,δD_(SMOW)为-129‰～-80‰,表明成矿流体主要为岩浆水和混合大气降水。方解石的δ~(13)C_(PDB)变化于-2.4‰～-1.4‰,δ~(18)O_(SMOW)为8.3‰～9.2‰,表明流体中的碳来自岩浆。对辉钼矿石英脉中辉钼矿进行了Re-Os同位素测年,获得等时线年龄为(378.3±5.6)Ma,与花岗闪长斑岩锆石SHRIMP U-Pb年龄(381～375 Ma)在误差范围内一致。早期成矿作用发生在中泥盆世,与斑岩有关,晚期叠加成矿作用发生在中、晚三叠世,与构造-岩浆-热液活动有关。  相似文献   

16.
研究了若尔盖铀矿田中灰岩、硅灰岩及方解石脉的碳氧同位素组成,结果表明产于地层中的灰岩、硅灰岩及方解石脉的δ13C值为-1.48‰～3.18‰,平均为1.51‰,为海洋沉积碳酸盐岩的碳同位素组成特征;δ18O值为-12.81‰～-3.71‰,平均为-9.92‰,在铀矿田中δ18O值最高.与成矿作用关系最为密切的含矿方解石脉δ13C值为-2.78‰～-4.81‰,平均为-3.93‰,明显表现为地幔来源的特点;δ18O值为-13.14‰～-15.05‰,平均为-13.87‰,其值在铀矿田中介于地层中岩石(脉)与矿区方解石脉之间.矿区方解石脉的δ13C值为-3.53‰～-6.35‰,平均为-4.93‰,与含矿方解石脉的碳同位素组成相近,表明其亦是成矿作用的产物;δ18O值为-16.00‰～-24.75‰,平均为-19.36‰,在铀矿田中δ18O值最低,明显表现为深部来源特征.综合若尔盖铀矿田的碳氧同位素组成特征,暗示其成矿流体应当来源于地幔.  相似文献   

17.
依据实测的塔里木盆地麦盖提斜坡玉北地区41个碳酸盐岩碳氧同位素数据,结合岩石学方法,研究了碳氧同位素的组成、演化及其地质意义。数据显示,δ~(13) C值主要分布在-2.6‰~0.7‰,均值为-1.0‰;δ~(18) O值分布在-9.4‰~-3.5‰,均值为-6.9‰。玉北地区古盐度为118.39~126.34,平均为121.94。奥陶系碳酸盐岩淡水改造作用明显。碳氧同位素的组成和演化不但可以指示沉积环境,而且还与生物生产率以及古海平面变化呈正相关性:δ~(13) C的低值对应于局限台地台内滩亚相沉积环境;δ~(13) C的高值对应于开阔台地滩间海、台内滩亚相沉积环境。碳氧同位素组成还对成岩环境有明显响应:鹰山组δ~(13) C与δ~(18) O均向高负值偏移,表明经历过强烈的表生岩溶作用;蓬莱坝组δ~(13) C低—中负值,δ~(18) O表现为高负值,在白云岩储层中可见鞍状白云石及燧石,主要为深埋藏成岩环境;良里塔格组同位素特征为δ~(18) O高负值,δ~(13) C低正值,并且在进入埋藏岩溶阶段之前还经历过风化壳岩溶作用。  相似文献   

18.
Petrography demonstrates the presence of three types of fibrous calcite cement in buildup deposits of the Kullsberg Limestone (middle Caradoc), central Sweden. Translucent fibrous calcite has intrinsic blue luminescence (CL) indicative of pure calcite. This cement has 2–5 mol% MgCO3, low Mn and Fe (≤ 100 p.p.m.), and is considered to be slightly altered to unaltered, primary low- to intermediate-Mg calcite. Grey turbid fibrous calcite has variable but generally low MgCO3 content (most analyses <2 mol%) and variable CL response, with Mn and Fe concentrations up to 1200 and 500 p.p.m., respectively. The heterogeneous characteristics of this variety of fibrous calcite are caused by diagenetic alteration of a translucent fibrous calcite precursor. Light-brown turbid fibrous calcite has low MgCO3 (near 1 mol%) and variable Mn (up to 800 p.p.m.) and Fe (up to 500 p.p.m.) concentrations, with an abundance of bright luminescent patches, which formed during alteration caused by reducing diagenetic fluids. The δ13C and δ18O values of all fibrous calcite form a tight field (δ13C=1·7 to 3·1‰ PDB, δ18O= ? 2·6 to ? 4·1‰ PDB) compared with fibrous calcite isotope values from other units. Fibrous calcite δ18O values are larger than adjacent meteoric or burial cements, which have δ18O δ ? 8‰ PDB. Consequently, most diagenetic alteration of Kullsberg fibrous calcite is interpreted to have occurred in the marine diagenetic realm. First-generation equant and bladed calcite cements, which pre-date fibrous calcite, are interpreted as unaltered, low-Mg calcite marine cements based on δ13C and δ18O data (δ13C = 2·3 to 2·7‰ PDB, δ18O= ? 2·8 to ? 3·5‰ PDB). Unlike fibrous cement, which reflects global sea water chemistry, first-generation equant and bladed calcite are indicators of localized modification of seawater chemistry in restricted settings. Kullsberg abiotic marine cements have larger δ18O values than most Caradoc marine precipitates from equatorial Laurentia. Positive Kullsberg δ18O values are attributed to lower seawater temperatures and/or slightly elevated salinity on the Baltic platform relative to seawater from which other marine precipitates formed.  相似文献   

19.
A carbonate buildup of Middle Triassic age, the Esino Limestone, outcrops in the Southern Calcareous Alps of Lombardy (N Italy). Along its margin and within the open subtidal facies, the Esino Limestone contains calcite cement-filled cavities of cm to m size. These features, known as evinosponges, may form pervasive networks within the host rock. The filling consists of concentric, isopachous layers of fibrous low-Mg calcite crystals characterized by strong undulose extinction and bent cleavages. The cement crusts are non-luminescent under cathodoluminescence, but both cements and host rock are cross-cut by micro-fractures filled with bright-luminescent calcite, related to late void-filling sparite. Mixing of different carbonates is reflected in stable isotope data. On the hand specimen scale, the oxygen and carbon isotope compositions of cements and host rock show little variation. When compared on a regional scale, the values cover a broad range from δ18O(PDB)=?5‰ to ?12‰ and from δ13O =0‰ to +3‰. The linear covariant trends defined by the oxygen and carbon isotope data for different sampling regions reflect the admixture of late, isotopically depleted calcite with an isotopically enriched non-luminescent calcite of early diagenetic origin. The Esino Limestone fibrous cements, which were probably precipitated in the marine or marine-meteoric phreatic environment, were affected by late diagenetic processes that caused mineral deformation and isotopic depletion through recrystallization and the admixture of a later calcite. These later calcites precipitated from penetrative fluids possibly related to Late Triassic volcanic activity and/or to the Late Cretaceous/Early Palaeogene alpine orogeny.  相似文献   

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