Geochemical characteristics of the Early Pliocene cold seep dolomite at Chiahsien, Taiwan and their implications for fluid sources and sedimentary environment
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摘要: 白云石成因一直是地学中尚未解决的难题,海底冷泉系统中发育的原生白云石为解决白云石成因问题提供了新途径。台湾甲仙白云仙谷早上新世盐水坑组页岩地层中发育有冷泉白云岩,其流体来源和沉积环境并不清楚。本文通过矿物学和岩石学,结合碳氧同位素、微量和稀土元素地球化学,探索该冷泉白云岩的流体特征和形成环境,为解决白云石成因提供参考。白云仙谷冷泉白云岩以烟囱状或透镜状产出于页岩中,碳酸盐矿物均为泥微晶白云石,含量为61.4%~88.0%。冷泉白云岩的δ13C为−27.08‰~−10.58‰,指示形成白云石的碳源可能是热成因甲烷和海水的混合。Ni/Co均值为12.54,稀土元素配分模式呈中稀土富集、无Ce异常,均表明冷泉白云岩形成于弱还原的沉积环境。在弱还原环境中的冷泉微生物的作用下,促进了HCO3−的增加和SO42−的消耗,可能有利于冷泉白云石的形成。Abstract: The origin of dolomite is a long-term argument in geology. In recent years, protodolomite has been discovered in hydrocarbon seeps, which provides critical evidence for solving the problem. Therefore, the authigenic carbonate found in hydrocarbon seeps is regarded as a kind of unique geochemical archives of fluid seeping in history. The carbonates studied in this paper occur as chimneys or lenses within the shale of Early Pliocene, the Yanshuikeng Formation, exposed at Chiahsien, southwestern Taiwan. Petrological and geochemical tests, such as petrography, mineralogy, carbon and oxygen stable isotopes, and rare earth element (REE) compositions, are made to trace the fluid sources and sedimentary environment. X-ray analyses suggest that the carbonate is mainly composed of dolomite (61.4%~88.0%). The δ13C values of dolomites range from −27.08‰ V-PDB to −10.58‰ V-PDB, suggesting a thermogenic methane and seawater associated carbon sources. The value of Ni/Co is around 12.54, and the original REE distribution shows a pattern of enrichment in the middle without Ce anomalies. All these results indicate that the Chiahsien dolomite was precipitated from reducing seep fluids. Under the action of microorganisms in the sub-reducing environment, HCO3− is increased and the SO42− more consumed, which is in favor of the formation of seep dolomites.
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Keywords:
- seep dolomite /
- carbon isotope /
- REE /
- Taiwan
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东海某凹陷低孔低渗储层油气资源丰富,但是主要油气层系存在砂泥岩层胶结疏松,砂泥岩层中夹煤层等现象,导致复杂的钻井情况,如何降低滤液对油气层的侵入影响,减少侵入深度,预防与控制水敏和液锁效应的发生是提高低孔低渗储层有效开发的重要手段[1-2],因此,优选了一套油包水钻井体系,井壁稳定性得到了改善,钻井周期明显缩短,储层保护取得显著成绩,但是更换泥浆体系对测井和录井也带来了新的问题,油基泥浆侵入对电阻率、中子、核磁仪器的响应与水基泥浆完全不同,此外气测录井和荧光录井资料受油基泥浆影响大[3-7]。本文通过对比水基泥浆和油基泥浆环境下测井和录井资料解释差异,探索东海地区在油基泥浆背景下的油气快速识别方法。
1. 水基泥浆与储层污染
水基泥浆的主要组成部分为水,除此之外还有少量添加剂(例如黏土剂、降滤失剂和防水锁剂等),水作为泥浆中分散相,主要以化学结构水、吸附水和自由水的形式存在,并且自由水的比重较大,一般占比70%~80%[1],因此,泥浆对地层的液相侵入严重,易造成储层污染。
东海某凹陷NBxx-5-1s井4 211~4 229 m岩心孔隙度分布范围为8%~10.7%,渗透率分布范围为0.18~5.4 mD,属于东海典型低孔低渗储层。储层的孔隙结构喉道细小,泥浆中固相颗粒侵入损害深度和程度有限,泥浆中自由水在正压差或者毛管力作用下侵入储层,驱替近井地带中天然气,侵入带水相饱和度增大,气相渗透率显著降低,水锁效应导致气井低产甚至无产[1-2]。
NBxx-5-1s井测井解释出两套气层,花港组的H6层和平湖组的P2层(图1),录井显示皆为细砂岩,H6和P2层自然伽马分布范围为40~70 API,平均为50 API,孔隙度分布范围为8%~11.2%,平均为9%,H6层电阻率分布范围为34~40 ohmm,P2层电阻率分布范围为40~61 ohmm;RCI测压显示H6层测压9个点,流度分布范围为2.3~3.3 mD/cp,平均为2.74 mD/cp,P2层测压8个点,流度分布范围为2.3~12.7 mD/cp,平均为8.89 mD/cp;经过对比,P2层的渗透性、电性特征,均优于H6层(表1),但是DST测试结果差异较大,P2层测试产气微量;H6层测试产气7.3万方/天。
表 1 NBxx-5-1s井DST2与DST3综合对比表Table 1. Comparison of DST2 and DST3 in NBxx-5-1s特征参数 DST2 DST3 P2 H6 射孔深度段(m) 4 198.0~4 220.0 4 439.4~4 470.2 4 228.1~4 237.0 4 239.8~4 248.1 4 475.3~4 493.8 4 258.1~4 261.8 4 265.2~4 277.0 射开厚度(m) 49.3 54.7 钻井泥浆比重(sg) 1.36 1.36 机械转速(m/h) 6~7.5 8~15 气测全量(%) 10~11.53 5~17.6 电阻率(Ω•m) 40~61 34~40 储层孔隙度(%) 8~11.2 8~11.2 测压流度(mD/cp) 2.3~12.7/平均8.89 2.3~3.3/平均2.74 核磁渗透率(mD)诱喷压差(Mpa) 5~1015.5 1~325.5 液垫 海水 柴油 射孔弹类型 692SD-127P-1 SDP45PYX39-3 射孔穿深(mm) 909 1 447 工作制度 二开二关 二开二关 通过对该井泥浆侵入分析,3 960~4 000 m地层在泥浆中浸泡后,复测电阻率P40H明显低于随钻电阻率P40H,复测电阻率A40H与随钻电阻率A40H无差异(图2),指示地层受到泥浆侵入明显,泥浆侵入深度大于P40H探测深度,小于A40H探测深度(地层电阻率为30 Ωm时,A40H径向探测深度为62 in(约157 cm),P40H径向探测深度为35 in(约88 cm)),推测泥浆侵入深度约1 m。H6层、P2层地层物性与3 960~4 000 m地层物性相近(孔隙度约10%,渗透率约3 mD),在相同泥浆比重背景下,推测泥浆侵入对储层的污染程度相近。
对比H6与P2地层的DST测试工艺(表1),P2层为高温地层(地层温度157 ℃),射孔采用超高温弹,超高温弹径向穿深0.9 m;H6层为常温地层(地层温度148 ℃),射孔采用普通弹药,弹药径向穿深1.5 m。根据上述对比结果,P2层射孔弹穿深有限,并且诱喷压差较小,原状地层天然气无法突破侵入带,在水锁效应下无法形成有效渗流,导致两次测试产能差异明显。
2. 油基泥浆对测井、录井的影响
为了满足东海地区低孔低渗储层保护的需要,优选了一套油包水钻井液体系,该体系的实验室基础配方如下:3#白油+3%主乳化剂+1%辅乳化剂+1%润湿剂+4%有机土+3%降滤失剂+2%碱度调节剂+2%封堵剂+2%疏水胶体封堵剂+0.5%流型调节剂+1.2%高温流变稳定剂+重晶石(油水比为80∶20)。新钻井液体系性能良好,在清洁井眼、泥浆滤失、携岩性等方面效果好,能保证井筒环境的稳定,为录井作业和测井作业提供良好环境,但是,泥浆体系的变化为测井和录井带来新的挑战。
2.1 油基泥浆对测井的影响
油基泥浆对电法测井影响较大,对放射性、声法测井影响小。水基泥浆测井仪器在油基泥浆环境中无法正常使用,目前一批油基泥浆测井仪器投入使用并推广,其中电阻率仪器在油基泥浆环境下的响应特征与水基泥浆不同,当钻遇水层时,电阻率曲线呈现分异特征。
利用泥浆滤失原理和电阻率仪器延时测井方式,观察电阻率分异特征,快速判别油气层和水层。储层流体为油气时,流体成分与油基泥浆类似均为非导电流体,泥浆滤失前后冲洗带泥浆电阻率无差异;储层流体为水时,流体成分与油基泥浆截然不同,泥浆滤失后,地层水的混入导致泥浆的油包水体系被打破,形成导电回路,泥浆滤失后冲洗带电阻率高于滤失前泥浆电阻率[7-10]。
NBxx-5-2井在油基泥浆环境下钻遇气层和水层(图3),4 449~4 474 m井段随钻与复测电阻率P16H重叠,地层流体为气,4 474~4 538 m井段随钻与复测电阻率P16H分异,且复测电阻率P16H高于随钻电阻率P16H,地层流体为水,电阻率梯度变化点为流体界面。4 471.5 m经过电缆泵抽取样(MDT仪器)(图4),泵抽至45 min时,井下流体实验室光谱分析仪得知,地层泵抽出流体为天然气和泥浆滤液,泵抽至160 min,泵抽压增大至4.13 Mpa,地层出现明显段塞流水信号,证实地层出水,与电阻率延时测井判断一致。
2.2 油基泥浆对录井的影响
研究区建立了水基泥浆环境下气测组分快速识别地层流体图版(图5),图版数据来源于研究区测试资料,并且划分3个区,分别为油区、凝析油气区、气区,根据气测组分计算组分中相对含量C1/C2+和C2+/C1+,再结合录井荧光信息,判断储层流体性质。研究区NBxx-5-1s井是水基泥浆,4 198~4 277 m井段录井无荧光显示(图1,表2),通过气测组分快速识别为气层,该井段经过测试,产气7.3万方/天,天然气为干气,甲烷含量91.61%。
表 2 NBxx-5-1s、NBxx-6-2录井荧光显示表Table 2. Logging fluorescence of NBxx-5-1s and NBxx-6-2井名 深度/m 岩性 荧光录井 直照 滴照 顶 底 颜色 面积/% 颜色 反应 NBxx-5-1s 4 198.0 4 238.0 灰白色/浅灰色细砂岩、泥质粉砂岩 无 / 无 / 4 240.0 4 248.0 浅灰色细砂岩 无 / 无 / 4 250.0 4 252.0 浅灰色细砂岩 无 / 无 / 4 258.0 4 264.0 灰色泥质细砂岩 无 / 无 / 4264.5 4 284.5 浅灰色粉砂岩、细砂岩 无 / 无 / NBxx-6-2 3 712.0 3 721.0 细砂岩 暗黄色 5 乳白色 慢 3 729.0 3 735.0 细砂岩 暗黄色 10 乳白色 慢 3 736.0 3 750.0 细砂岩 暗黄色 10 乳白色 慢 3 761.0 3 766.0 细砂岩 暗黄色 5 乳白色 慢 3 775.0 3 797.0 细砂岩 暗黄色 5 乳白色 慢 由于油基泥浆的推广,气测组分和荧光信息受到泥浆影响,导致研究区快速识别图版适用性受到限制。NBxx-6-2井3 712~3 797 m井段录井荧光暗黄色,发光面积5%~10%(图6,表2),荧光显示十分丰富。通过气测组分快速识别,3 743.5 m落点于凝析油气区,该点MDT泵抽,井下流体实验室测量得到稳定地层流体组分,计算气油比为319.2 m3/m3,测量油密度为0.61 g/m3,证实地层流体为油,并非凝析油;通过气测组分快速识别,3 760 m落点于气区,该点泵抽气油比13 523.9 m3/m3,证实地层流体为气(表3),流体性质判断正确,但与录井中荧光显示活跃矛盾。因此,认为在钻井过程中,岩石破碎气中的气体组分被油基泥浆不等比吸收,导致气测组分中的相对含量失衡,产生误判,并且油基泥浆中白油组分含少量芳香烃,存在荧光现象,导致录井过程中荧光信息丰富。
表 3 NBxx-6-2井3 743.5 m泵抽信息表Table 3. MDT pumping information, depth of 3 743.5 m, Well NBxx-6-2深度/m 探针类型 流度 泵抽时间 泵抽体积/L 取样情况 IFA流体识别结论 GOR气油比/(m3/m3) 3 743.5 椭圆形探针 83.96 73 28.6 2PVT 油层 319.2 3 760 椭圆形探针 66.7 57 11 1PVT 气层 13 523.9 3. 不同泥浆体系测录井综合对比
3.1 井筒环境对比
东海地区主要油气层层段以砂泥岩为主,砂泥岩薄互层夹煤层时常发育,钻井过程中泥岩和煤层剥落掉块、泥岩分散造浆易形成钻井卡阻、井径扩大等复杂情况,油基泥浆为油包水体系,滤失低,摩阻低,携岩性强,电稳定性好,具备良好的井筒清洁作用和储层保护能力,能改善钻井环境,缩短钻井周期。油基泥浆推广以来,在东海应用于多口井,表4为研究区油基泥浆3口井与水基泥浆1口井钻井周期对比,油基泥浆钻井周期明显缩短。图7为4口井的井径曲线对比,油基泥浆井壁更清洁,井眼环境更好。
表 4 研究区4口井钻井周期对比Table 4. Comparison of drilling cycles for the four wells from the research area井名 完钻井深/m 钻井天数 备注 NBxx-5-1s 4 850 59 水基泥浆 NBxx-7-1 4 480 20 油基泥浆 NBxx-5-2d 4 680 15 油基泥浆 NBxx-5-3 4 500 28 油基泥浆 3.2 油气水层解释对比
油基泥浆与水基泥浆在井筒环境下均会有滤失性,钻遇渗透性好的储层,不同径向探测深度电阻率呈现出分异现象。水基泥浆环境下,钻遇油气层时,由于地层流体导电性差,泥浆侵入地层后,探测深度深的电阻率一般大于探测浅的电阻率,即电阻率“低侵”现象;油基泥浆环境下,钻遇水层时,由于油基泥浆导电性差,泥浆侵入地层后,探测深度深的电阻率一般小于探测深度浅的电阻率,即电阻率“高侵”现象。对比了研究区2口井的电阻率“低侵”与“高侵”现象(图8),依图所示水基泥浆“低侵”现象明显,该现象普遍应用于渗透层的识别,并非油气水层识别,油基泥浆“高侵”现象能较好识别渗透性水层,结合延时测井,可以有效区分油气层与水层。
东海低孔低渗背景下的油层与气层识别是难点,地层中流体性质变化快,且油层与气层测井特征相似,很难快速识别。水基泥浆环境下,泥浆主要为海水和少量添加剂,组分中无荧光信息,录井过程中荧光信息主要反映地层流体荧光信息,并且气测组分中相对含量能反映地层中轻质与重质分布,利用区域经验图版结合荧光信息能较好识别储层流体性质;油基泥浆环境下,白油为主要组成部分,白油成分中含有少量的芳香烃,具有一定荧光特性,并且油基泥浆不等比吸收岩石破碎气,利用区域经验图版判断储层流体性质受到局限,需要建立油基泥浆环境下的区域经验图版,结合精度更高的三维荧光信息,综合判断储层流体性质[11-16]。
3.3 储层物性评价
油基泥浆钻井能提供状态良好、稳定的井壁环境,测井仪器记录地层信息的准确程度得到保障,像常规测井中的自然伽马、阵列声波、岩性密度等,均能得到品质为优的资料。但是对于测量地层含氢指数信息的仪器,像中子仪器、核磁仪器需要做井场环境校正(含氢校正)。
渗透性地层一般都有泥浆侵入,中子测井探测范围内的流体被认为是侵入带,油基泥浆滤液与地层流体的混合造成含氢量略低于淡水含氢量,通过对比邻井相同层位,水基泥浆环境下中子响应值,现场对油基泥浆下的中子做进场环境校正[7-10]。依据NBxx-7-1井现场测井图(图9),CNC2为油基泥浆校正后的中子,相比原始测量中子CNCF略大,在做储层定量评价计算孔隙度时使用环境校正后的中子曲线,能保证储层物性计算更准确。
核磁测井不受岩石骨架影响,广泛应用于储层评价中,特别是孔隙结构复杂的低孔低渗储层。核磁仪器的径向探测深度为井周5~10 cm,井周极易被泥浆充填,核磁测量的T2谱信息中包含泥浆信息。水基泥浆环境下,泥浆主要成分为水,T2谱的分布基本不受影响,主要反映储层中不同尺寸孔隙分布,大孔隙驰豫时间长,小孔隙驰豫时间短;油基泥浆环境下,泥浆主要成分为油,T2谱受泥浆黏度影响,出现谱峰后移现象,造成大孔隙假象。
NBxx-5-1s井为水基泥浆环境下二维核磁(MReX)测量,该层段为气水分异明显的底水气藏(图10),砂体A为气层,砂体B为含气水层,两段砂体的T2谱谱峰分布相似性较高,地层含气性的改变并未影响T2谱分布,4 212~4 230 m砂体T2谱谱峰分布与岩心物性吻合良好。近井地带水基泥浆驱替地层流体,核磁探测范围为泥浆信息,地层含气性被泥浆信息覆盖。因此,水基泥浆环境下核磁T2谱能反应低孔低渗储层孔隙结构分布。
NBxx-6-2井为油基泥浆环境下二维核磁(MReX)测量,该层段为气、油、水三相分异的油气藏(图11),核磁T2谱谱峰出现明显后移,物性好、大孔隙发育段,T2谱形态宽缓,物性差、小孔隙发育段,T2谱形态窄陡。地层流体性质变换并未影响T2谱分布,但泥浆体系变换引起T2谱谱峰后移,并存在“拖曳”现象。因此,油基泥浆环境下核磁T2谱受泥浆影响较大,T2谱谱峰相对位置关系不能直接反应低孔低渗储层孔隙结构分布,谱峰形态特征能表征孔隙发育情况。
油基泥浆会影响核磁T2谱分布,通过核磁T2谱评价储层的有效孔隙度、总孔隙、束缚水等参数时,需要进行含氢校正,目前Baker公司MReX仪器的含氢校正是针对评价参数的含氢校正,含氢校正后核磁有效孔隙度大于校正前有效孔隙度。
3.4 储层渗透性评价
电缆地层测试是一种测井作业,是目前唯一能进行动态地层测试的作业。东海常用的电缆地层测试仪器包括斯伦贝谢的MDT仪和贝壳休斯的RCI仪,本次研究不讨论公司之间仪器的工作原理和系统差异,仅从测压资料的解释上分析水基泥浆和油基泥浆给电缆地层测试带来的影响。
根据达西定律可知,储层有效渗透率为一定压力降下,地层流体流过探针的流量,压降流度定义为,地层有效渗透率除以黏度[17-20],一般用M表示(式1),压降流度是储层有效渗透率和黏度的综合反映,并且探针刺破泥饼,座封后形成冲洗带封闭环境,冲洗带流体为泥浆滤液和原装地层流体的混合液,因此,压降流度信息与泥浆黏度有密切关系。
$$ M = \frac{K}{\mu } = C\frac{q}{{2{\rm{\pi }}{r_p}*\Delta P}} $$ (1) 式中,M为测压流度,mD/cP;K为有效渗透率,μm2;μ为黏度,cP;q为压降流速,cm3/s;rp为探针半径,cm;Δp为压差Mpa;C为仪器形状系数,不同探针有不同的数值,无量纲。
一般情况下,室温条件下水基泥浆黏度为1 cp,而油基泥浆黏度为2~5 cp,鄢捷年[4]认为,油包水乳化钻井液表观黏度随温度的升高而降低,随压力的增大而增大,但是在井底条件下,表观黏度受到温度的变化大,压力的作用减小。因此推测,水基泥浆和油基泥浆在地层条件下,黏度均存在降低的现象,根据公式1推导,认为油基泥浆条件下测量得到储层流度略低于相同物性储层水基泥浆条件下流度,因此,在低孔低渗储层油基泥浆条件下,分析流度信息时,应客观估算储层的渗流能力,这对储层有效产能估算有指导意义。
图12为东海某凹陷斜坡带选取相近构造6口井的低孔低渗储层(15%>孔隙度≥10%,10 mD>渗透率≥0.1 mD)流度信息与岩心空气渗透率交会图,在低孔低渗储层背景下,油基泥浆条件下相同流度对应的岩心空气渗透率更高。水基泥浆条件下岩心的空气渗透率是流度信息的大约1~2倍关系,油基泥浆条件下岩心的空气渗透率是流度信息的大约3~5倍关系,这都与泥浆体系的黏度有关系,因此,在评估储层的渗透性时,应区分泥浆体系和泥浆黏度信息,为估算储层产能提供有效依据。
4. 结论
(1)油基钻井液具备优良的泥浆性能,保证了井筒环境清洁型,为录井作业和测井作业提供了良好的环境;
(2)油基泥浆环境下利用延时测井能较好的区分油气层与水层,油层与气层区分应建立油基泥浆环境下区域经验图版;
(3)油基泥浆环境下测井资料质量优,但是中子、核磁仪器需要做含氢校正;
(4)油基泥浆环境下,利用测压资料估算储层渗透性,需要明确泥浆体系与泥浆黏度信息。
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图 2 甲仙冷泉碳酸盐岩剖面野外特征
A.层状碳酸盐岩,位于白云仙谷谷底;B.丘状碳酸盐岩,风化较为严重,位于冲沟崖处;C.透镜状碳酸盐岩,位于冲沟崖处,围岩为固结程度较好的黑色页岩,直径约为50 cm;D.冷泉碳酸盐岩生物丘,含满月蛤科的Lucinoma化石及其印模,位于白云仙谷山坡处。
Figure 2. Field geological characteristics of Chiahsien seep carbonate
A. layered carbonates at the bottom of the Baiyunxiangu Valley; B. colluvial carbonates with seriously weathering at the gully cliff; C. lenticular carbonates at the gully cliff with well-consolidated black shale of about 50 cm in diameter; D. cold-seep carbonates biodomes, containing Lucinoma, on the slopes of the Baiyunxiangu Valley.
图 3 甲仙代表性自生碳酸盐岩手标本、抛光面及矿物特征
A.碳酸盐岩发育不同期次的沉积物;B.冷泉碳酸盐岩发育烟囱结构;C.呈现两种不同的组分,左侧为陆源碎屑含量较高的黑色泥晶,右侧为灰色微晶,可能由重结晶作用形成;D.冷泉白云岩含有大量生物碎屑,可见清晰的有孔虫化石和黄铁矿颗粒。
Figure 3. Representative hand specimens, polished surface and mineral characteristics of the Chiahsien seep carbonates
A. sediments of different periods in the carbonates; B. chimney structures in the cold-seep carbonates; C. black fine crystals with high content of terrigenous detritus on the left and gray microcrystal on the right, which may be formed by late-stage recrystallization; D. the cold-seep dolomite contains a large amount of biological detritus, with well-preserved foraminifera and pyrites.
图 5 甲仙冷泉白云岩稀土元素特征
A.稀土元素分布模式图,B.稀土元素Ce/Ce*与Pr/Pr*相关图。I 区:无异常;IIa 区:La正异常,无Ce异常;IIb区:La负异常,无Ce异常;IIIa区:真Ce正异常;IIIb区:真Ce负异常[60]。
Figure 5. Characteristics of REE of the Chiahsien seep dolomite
A.PAAS-normalized REE distributions of Chiahsien seep carbonate; B.Ce/Ce* vs. Pr/Pr* diagram of Chiahsien seep carbonates. Field I: no anomaly; Field IIa: positive La anomaly causes apparent negative Ce anomaly; Field IIb: negative La anomaly causes apparent positive Ce anomaly; Field IIIa: real positive Ce anomaly; Field IIIb: real negative Ce anomaly[60].
表 1 甲仙地区冷泉白云岩矿物学组成及碳氧同位素
Table 1 Mineralogical composition of the Chiahsien seep dolomite and carbon and oxygen isotope
样品号 方解石/% 白云石/% 石 英/% 伊利石/% 绿泥石+蒙脱石/% 钠长石/% δ13C/‰ δ18O/‰ BG-1 88.0 9.0 3.0 -20.42 2.06 BG-2 80.7 9.0 4.0 6.3 -20.48 1.98 BG-3 52.3 28.3 19.4 BG-4 82.7 12.9 4.3 -21.63 0.41 BG-5 83.6 7.8 4.0 4.6 BG-6 76.3 8.6 10.9 4.2 BG-7 73.8 6.5 13.1 4.0 2.6 BG-9 10.2 61.4 14.8 5.0 5.0 3.6 -10.62 -2.72 BG-10 78.7 13.4 7.9 BG-11 64.9 25.5 9.6 BG-12 78.7 9.5 11.8 -27.08 0.90 表 2 甲仙白云仙谷的冷泉白云岩的主量元素和微量元素含量
Table 2 Major and trace element compositions of the Chiahsien seep dolomite
样品号 BG-1 BG-2 BG-4 BG-9 BG-10 BG-11 BG-12 MnO/% 0.06 0.07 0.09 0.10 0.09 0.07 0.12 Sr/(μg/g) 291.16 296.37 226.96 218.85 408.65 244.33 394.45 Mn/Sr 2.53 2.89 4.86 5.60 2.70 3.51 3.73 Li/(μg/g) 4.20 2.95 3.03 4.53 3.28 2.42 3.27 Be/(μg/g) 1.27 0.74 0.84 0.91 1.09 0.97 1.09 Sc/(μg/g) 7.21 6.89 8.25 7.38 6.24 5.90 6.24 V/(μg/g) 6.28 4.66 13.00 10.10 13.10 10.10 13.10 Cr/(μg/g) 10.30 9.75 10.90 7.60 10.40 9.44 10.40 Co/(μg/g) 9.61 2.06 3.26 2.89 3.59 3.38 3.59 Ni/(μg/g) 51.70 49.60 49.70 38.70 44.60 35.00 44.60 Cu/(μg/g) 0.48 0.36 0.40 1.26 0.61 1.02 0.61 Zn/(μg/g) 3.20 1.94 2.09 1.72 5.71 0.09 5.71 Ga/(μg/g) 0.39 0.43 0.45 0.56 0.52 0.41 0.83 Rb/(μg/g) 4.41 3.73 4.63 5.69 3.41 2.92 7.20 Zr/(μg/g) 0.23 0.31 0.34 0.17 0.66 0.37 1.16 Nb/(μg/g) 0.03 0.02 0.03 0.01 0.04 0.03 0.20 Cs/(μg/g) 0.04 0.05 0.05 0.05 0.05 0.04 0.19 Ba/(μg/g) 23.00 16.00 22.00 18.00 23.00 20.00 32.00 Hf/(μg/g) 0.03 0.02 0.02 0.03 0.03 0.03 0.05 Pb/(μg/g) 0.04 0.24 0.21 0.37 0.49 0.19 0.23 Th/(μg/g) 1.20 1.10 1.84 3.16 1.26 1.51 1.52 U/(μg/g) 0.63 0.55 4.61 0.53 2.32 5.77 0.78 Ni/Co 5.38 24.08 15.25 13.39 12.42 10.36 12.79 表 3 甲仙白云仙谷的冷泉白云岩的稀土元素含量
Table 3 Rare element compositions of the Chiahsien seep dolomite
样品号 BG-1 BG-2 BG-4 BG-9 BG-12 La/(μg/g) 3.28 2.16 3.64 4.16 4.54 Ce/(μg/g) 7.36 5.21 8.58 10.08 13.5 Pr/(μg/g) 0.9 0.67 1.05 1.34 1.03 Nd/(μg/g) 3.93 2.83 4.49 6.09 4.95 Sm/(μg/g) 0.97 0.66 0.99 1.48 1.17 Eu/(μg/g) 0.3 0.19 0.29 0.45 0.37 Gd/(μg/g) 1.24 0.77 1.17 1.67 1.48 Tb/(μg/g) 0.17 0.1 0.16 0.23 0.21 Dy/(μg/g) 1.01 0.52 0.83 1.14 1.15 Y/(μg/g) 9.03 4.52 7.41 7.75 10.2 Ho/(μg/g) 0.18 0.09 0.15 0.18 0.22 Er/(μg/g) 0.52 0.24 0.39 0.49 0.62 Tm/(μg/g) 0.06 0.03 0.04 0.06 0.08 Yb/(μg/g) 0.4 0.17 0.25 0.33 0.51 Lu/(μg/g) 0.06 0.02 0.03 0.04 0.08 ΣREE/(μg/g) 20.37 13.66 22.06 27.74 29.91 Ce/Ce* 0.97 1.00 1.00 0.96 1.33 lg(Ce/Ce*) 0.02 0.00 0.00 0.02 0.12 Pr/Pr* 0.98 1.02 0.99 0.99 0.74 (Pr/Sm)N 0.58 0.64 0.67 0.57 0.55 (Sm/Yb)N 1.24 2.03 2.02 2.30 1.16 -
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