Evidence of palaeoseismicity in a flowstone of the Observatoire cave (Monaco)

Abstract

Monaco is a medium seismicity zone. The Observatoire cave, a well decorated show cave, is a good place for palaeoseismicity studies. On the floor of the cave it is possible to observe a great number of collapsed sodastraws. The breakages are attributed to the 1887 Ligurian earthquake. A borehole in a flowstone shows several levels of collapses that may indicate ancient earthquakes. © Elsevier, Paris     

福建仙云洞现代次生碳酸盐团簇同位素特征与温度重建

碳酸盐团簇同位素（Δ₄₇）是基于碳酸盐中¹³C-¹⁸O丰度相较于其随机分布状态的偏离程度对温度进行估算的新型测温技术。洞穴石笋沉积过程复杂,部分石笋受动力分馏作用影响导致其碳酸盐Δ₄₇偏离平衡体系,这些因素增大了利用石笋碳酸盐Δ₄₇定量重建古温度的难度。本研究以典型东亚夏季风影响区的福建仙云洞为研究对象,通过对该洞现代次生碳酸盐样品的采集和稳定同位素组成的测定,探讨研究区现代次生碳酸盐Δ₄₇特征及其重建温度的可靠性。研究结果表明：1）仙云洞5个现代次生碳酸盐样品的Δ₄₇和δ¹⁸O结果均较为集中,而δ¹³C差异较大,这种样品间差异与共性并存的特征表明本研究所选样品具有代表性;2）仙云洞5个现代次生碳酸盐样品的Δ₄₇值在0.702‰~0.720‰范围内波动,实测温度与基于平衡体系下建立的团簇同位素温度转换方程计算的温度结果较为一致,揭示出该洞穴现代次生碳酸盐Δ₄₇接近热力平衡,不存在显著的动力分馏;3）基于洞穴次生碳酸盐的团簇同位素温度和δ¹⁸O值,推算出对应的滴水δ¹⁸O值介于-8.0‰~-7.6‰之间,这与长期监测的仙云洞滴水δ¹⁸O结果较为吻合,表明仙云洞现代次生碳酸盐氧同位素接近同位素平衡。本文研究结果为重建区域古温度和古降水提供了证据支撑。     

A multiple cave deposit assessment of suitability of speleothem isotopes for reconstructing palaeo‐vegetation and palaeo‐temperature

The suitability of speleothems for interpreting palaeoclimate is typically determined by using either the Hendy Test, overlapping analysis or long‐term cave environment monitoring. However, in many cases, these methods are not applicable, because a speleothem lacks clearly traceable layers for the Hendy Test, it is difficult to obtain an overlapping speleothem nearby, or long‐term cave monitoring is impractical. The authors propose a multiple cave deposit approach to assess the suitability of speleothems for palaeoclimate study. Speleothems collected from two sites within Raccoon Mountain Cave, Tennessee (USA) exhibit remarkable spatial variation (δ¹³C: ?10·3‰ to ?2·2‰) over a relatively short distance (ca 260 m). Drip water δ¹⁸O values exhibit a seasonal precipitation signal at Site 1 and an annual signal at Site 2. Combining field observations, water isotope analysis and trace‐element data, the authors propose that the speleothem formation at Site 1 and Site 2 tapped distinct sources of CO₂: (i) CO₂ derived from overlying soils for Site 1; and (ii) limestone dissolved inorganic carbon induced by ground water dissolution for Site 2. Using fresh cave deposits (modern speleothem) δ¹³C (100% C3 vegetation) as an analogue, a simple model was developed to estimate land surface vegetation for speleothems. The speleothem formation temperature estimated using fresh cave deposit δ¹⁸O values generally reflects the mean annual temperature in this region. This study indicates that spatial variations in carbon isotopes could be caused by different carbon sources dominating in different parts of the cave, which should be taken into consideration by researchers when using speleothem δ¹³C values to reconstruct temporal palaeo‐vegetation changes. This study demonstrates a practical sampling strategy for verifying suitability of speleothems for palaeo‐vegetation and palaeo‐temperature reconstructions by analysing multiple cave deposits, especially for cases in which the Hendy Test, parallel sampling and long‐term monitoring of cave environment are not feasible.     

电气石—水体系中D／H交换动力学研究

本文对电气石-水体系氢同位素动力分馏进行了实验研究。研究表明,电气石-水体系氢同位素交换以扩散交换为主。在温度为800～450℃范围内,该体系的氢扩散动力学方程为:logD=-5.96-6.68×10~3/T(圆柱模式),logD=-5.64-6.42×10~3/T(薄板模式),扩散活化能为128.0 kJ/mol(圆柱模式)和123.1 kJ/mol(薄板模式)。     

矿物-水体系氢同位素平衡分馏和动力分馏的实验研究

矿物水体系氢同位素平衡分馏系数和动力分馏系数是同位素地球化学研究中的重要参数。这些参数大多由实验测定。氢同位素分馏的实验研究主要包括矿物水体系氢同位素交换实验,交换实验前后矿物、水的氢同位素分析及分馏机理、平衡分馏、动力分馏理论研究。为确保氢同位素分馏系数和一系列动力学参数的准确可靠,实验中防止氢透过容器壁扩散,避免空气中水汽污染样品,正确控制实验温度等都很重要。本研究以石英管代替前人常用的金（银、铂）管作反应容器,建立了一套实验研究羟基矿物水体系氢同位素平衡分馏和动力分馏的新方法,并开展了电气石水、黑柱石水体系氢同位素分馏的实验研究。所得一系列参数的精度明显好于国外报道的资料。此研究方法可广泛应用于羟基矿物水体系的氢同位素分馏的实验研究。     

Variation of summer precipitation δ18O on the Chinese Loess Plateau since the last interglacial

Orbital-scale East Asian Summer Monsoon (EASM) variations inferred from loess deposits in northern China and speleothems from southern China display different dominant periods, complicating our understanding of monsoon response to insolation and ice-volume forcings. Here we integrate a new microcodium δ¹⁸O record from a high-resolution last interglacial loess profile with previously published data and provide a composite microcodium δ¹⁸O record on the Chinese Loess Plateau (CLP) since the last interglacial. The composite microcodium δ¹⁸O record displays distinct precessional cycles, consistent with speleothem δ¹⁸O records, but with different amplitude contrast (particularly during the peak interglacials). We propose that both loess and speleothem δ¹⁸O records exhibit covariations at precessional timescale oscillations. The discrepancy between loess and speleothem from southern China can be attributed to the influences of other processes besides summer precipitation on the proxies. A slight difference in amplitude between microcodium and speleothem δ¹⁸O records implies that the EASM is also influenced by inland surface boundary conditions, which has important impacts on the occurrence of EASM precipitation. Therefore, microcodium δ¹⁸O from the Chinese loess–paleosol sequences can be regarded as a representative proxy of EASM precipitation in northern China and then a reliable proxy reflecting the variation of EASM intensity.     

Origin and palaeoenvironmental significance of lamination in stalagmites from Katerloch Cave,Austria

The origin and environmental dependencies of lamination in stalagmites from Katerloch, common in speleothems from other cave sites, are examined in detail. Petrographic observations and chemical analyses (including isotopes) of stalagmites and modern calcite were combined with multi‐annual cave monitoring. All investigated stalagmites are composed of low‐Mg calcite and show white, porous laminae and typically thinner, translucent dense laminae. The binary lamination pattern results from changes in the calcite fabric: white, porous laminae are characterized by a high porosity and abundant fluid inclusions and also by enhanced vertical growth and thinning towards the flanks. Translucent, dense laminae exhibit a compact fabric and constant thickness of individual growth layers. U‐Th dating supports an annual origin of the lamination and the seasonally changing intensity of cave ventilation provides a robust explanation for the observed relationships between lamination, stable C isotopic compositions and trace elements (Mg, Sr and Ba). The seasonally variable air exchange, driven by temperature contrasts between the cave interior and outside atmosphere, modulates the rate and amount of CO₂ degassing from the drip water and affects the hydrochemistry and consequently the fabric of the precipitating calcite. Although cave air composition and drip rate are both major variables in controlling CO₂ degassing from the drip water, the seasonally changing ventilation in Katerloch exerts the primary control and the results suggest a secondary (amplifying/attenuating) influence of the drip rate. Drip rate, however, might be the controlling parameter for lamina development at cave sites experiencing only small seasonal cave air exchange. Importantly, the seasonally variable composition of drip water does not reflect the seasonal cycle of processes in the soil zone, but results from exchange with the cave atmosphere. The alternating porous and dense calcite fabric is the expression of a variable degree of lateral coalescence of smaller crystallites forming large columnar crystals. The white, porous laminae represent partial coalescence and form during the warm season: low calcite δ¹³C values are linked to low δ¹³C values of cave air and drip water during that time. This observation corresponds to times of reduced cave ventilation, high pCO₂ of cave air, low drip water pH, lower calcite supersaturation and typically high drip rates. In contrast, the translucent, dense laminae represent more or less complete lateral coalescence (inclusion‐free) during the cold season (high calcite, drip water and cave air δ¹³C values), i.e. times of enhanced cave ventilation, low cave air pCO₂, increased drip water pH, relatively high calcite supersaturation and typically low drip rates. In essence, the relative development of the two lamina types reflects changes in the seasonality of external air temperature and precipitation, with a strong control of the winter air temperature on the intensity of cave‐air exchange. Thick translucent, dense laminae are favoured by long, cold and wet winters and such conditions may be related closely to the North Atlantic Oscillation mode (weak westerlies) and enhanced Mediterranean cyclone activity during the cold season. Studies of speleothem lamination can thus help to better understand (and quantify) the role of seasonality changes, for example, during rapid climate events.     

同步变化的东亚季风和印度季风:来自年层石笋氧同位素的证据

印度季风和东亚季风是亚洲季风的两个子系统.现代器测数据和地质历史重建记录均证明两个季风在季节和轨道尺度上具有相同的特征.然而,在年一年代际尺度上,两者的相互关系尚不清楚.笔者通过比较两个分别来自印度季风区(阿曼Defore洞)和东亚季风区(中国和尚洞)的超高分辨石笋氧同位素序列,研究780 a以来印度和东亚季风变化及其相互作用.阿曼石笋氧同位素记录印度季风的变化,而和尚洞石笋δ18 O则是东亚季风变化的指示器.笔者发现,在年代际尺度上阿曼石笋和中国石笋具有相同的氧同位素组成变化特征,同时反映了亚洲季风的强弱变化,表明了印度季风和东亚季风变化是同步的.     

云南呈贡龙潭山 1 号洞堆积物的铀系年龄

测定了人类化石地点云南呈贡龙潭山1号洞5个次生碳酸盐样的质谱法铀系年代。其中位于含人牙化石的II 堆积层下界面不远处的L TSY- 3石笋样质谱230 Th /234U 年龄为( 305± 15) ka; 而其余4 个样品经现场地层复核,它们与堆积均缺乏明确的叠压关系,因此认为它们很可能源自洞顶或洞壁石幔。此外,还测定了该地点5个动物化石样的230 Th /234 U 年龄,其结果为60～ 80 ka,平行测定了其中3 个样品的227 Th /230 Th 年龄,二种铀系年龄均在± 1. 5σ范围内一致,从而支持了该地点骨化石样铀系年代的可信度。在没有进一步的地层和年代证据之前,暂将60～ 80 ka 作为含人牙化石的第I I层堆积的年代应是合理的。但值得指出的是,由于骨化石中铀循环模式的不确定性,与有明确层位意义的钙板相比,洞穴地点的这类材料年代结果往往偏于年轻,因此上述年代测定结果很可能也存在偏低问题。      

Boron-isotope fractionation between tourmaline and fluid: an experimental re-investigation

The fractionation of boron isotopes between synthetic dravitic tourmaline and fluid was determined by hydrothermal experiments between 400 and 700°C at 200 MPa and at 500°C, 500 MPa. Tourmaline was crystallized from an oxide mix in presence of water that contained boron in excess. In one series of experiments, [B]_fluid/[B]_tour was 9 after the run; in another series it was 0.1. All experiments produced tourmaline as the sole boron-bearing solid, along with traces of quartz and talc. Powder XRD and Rietveld refinements revealed no significant amounts of tetrahedrally coordinated boron in tourmaline. ¹¹B always preferentially fractionated into the fluid. For experiments where [B]_fluid/[B]_tour was 9, a consistent temperature-dependent boron isotope fractionation curve resulted, approximated by Δ¹¹B_{(tour–fluid)} = −4.20 · [1,000/T (K)] + 3.52; R ² = 0.77, and valid from 400 to 700°C. No pressure dependence was observed. The fractionation (−2.7 ± 0.5‰ at 400°C; and −0.8 ± 0.5‰ at 700°C) is much lower than that previously presented by Palmer et al. (1992). Experiments where [B]_fluid/[B]_tour was 0.1 showed a significant larger apparent fractionation of up to −4.7‰. In one of these runs, the isotopic composition of handpicked tourmaline crystals of different size varied by 1.3‰. This is interpreted as resulting from fractional crystallization of boron isotopes during tourmaline growth due to the small boron reservoir of the fluid relative to tourmaline, thus indicating larger fractionation than observed at equilibrium. The effect is eliminated or minimized in experiments with very high boron excess in the fluid. We therefore suggest that values given by the above relation represent the true equilibrium fractionations.     

重庆芙蓉洞滴水现代次生化学沉积物沉积速率与元素特征

为了探讨芙蓉洞现代沉积物沉积速率和微量元素 (Mg,Sr) 的变化特征、控制机制以及气候环境指示意义,于2010年11月到2013年11月对芙蓉洞5个滴水点进行连续现场监测,并采集现代沉积物样品进行沉积速率计算和微量元素测定。结果显示:(1) 芙蓉洞5个滴水点的现代沉积物沉积速率与滴量、pH、Ca2+浓度以及PCO2等指标的关系表现出多样性。 其中MP4和MP5的沉积速率均与滴量呈正相关 (r=0.75, n=11, p<0.01; r=0.63, n=11, p<0.05),两个滴水点的沉积速率整体表现出雨季高、旱季低的变化规律,表明MP4和 MP5的沉积作用主要发生在雨季,其沉积速率的变化可以对季节性干湿度变化做出响应。(2) 2012-2013年年降水量明显增加,在稀释作用、水岩作用以及植物对元素差异性吸收作用的影响下,各滴水点现代沉积物整体呈现出Mg浓度减小而Sr浓度增大的趋势,Mg/Ca和Sr/Ca比值呈反相关关系,它们响应了年际尺度上降水量增加的气候信息。      

Evidence of Younger Dryas and Neoglacial cooling in a Late Quaternary palaeotemperature record from a speleothem in eastern Victoria,Australia

A calcitic stalagmite collected from a limestone cave in the Buchan area of eastern Victoria has been dated by three mass-spectrometric uranium series analyses. Two growth phases are represented: the older from 13.4 to 10.6 ka and the younger from 3.2 to 2.1 ka. Oxygen isotope analysis reveals that temperatures were below present-day values at all times, but particularly cool conditions are indicated between 12.3 and 11.4 ka, and Neoglacial conditions occurred at about 3 ka. The older cold climate event is clearly synchronous with the Younger Dryas in Europe and this is the first time that strong evidence for this event has been found in Australia. Carbon isotope variations are interpreted as indicating changes in plant productivity on the surface and are most likely controlled by variations in summer rainfall. They indicate particularly high levels of plant productivity from 11.5 to 11.0 ka. © 1996 John Wiley & Sons, Ltd.     

大气降水中氧同位素分馏过程的数学模拟

本介绍的数学模型考虑了混和云中冰水共存时，冰面过包头和环境下动力同位素的分馏机制。在等压冷却过程中，当取云中含水量系数Ａ１／４，Ｂ＝１／５，冰面过饱和度Ｓｉ＝０．０５＋０．９６９ｅｘｐ（－０．０８ｔ）时，由模型推算出的理论曲线与中高纬度地区的回归线有很好的一致性。从而说明，改进的数学模型具有实用意义。该模型还为中低纬度地区存在的降水量效应提供了理论依据。     

贵州纳朵洞洞穴滴水、现代沉积物δ18O特征及其环境意义

为了研究洞穴滴水及其对应的现代沉积物氧同位素的变化特征和对外界气候环境的指示意义,文章对贵州纳朵洞洞外大气降水、洞穴池水、6处滴水点及其对应的现代沉积物氧同位素进行了近2年的监测。结果显示纳朵洞外大气降水和洞穴池水δ18O值均呈现旱季偏重,雨季偏轻的季节特征,基本能反映洞穴所在区域的气候变化。而滴水沉积物δ18O值和滴水δ18O值自身存在协调同步的季节特征,但二者δ18O值与大气降水δ18 O值却呈现反向的季节变化,这可能是区域地形、岩溶表层带的调节和大气环流共同作用的结果。      

Isotopic climate record in a Holocene stalagmite from Ursilor Cave (Romania)

The PU‐2 stalagmite from Ursilor Cave provides the first dated Romanian isotope record for the Holocene. The overall growth rate of the speleothem was 3.5 cm kyr^?1, corresponding to a temporal resolution of 142 y between each isotope analysis. The ‘Hendy’ tests indicate that isotopic equilibrium conditions occurred during the formation of PU‐2, and hence that it is suitable for palaeoclimatic studies. The relationship between δ¹⁸O and temperature was found to be positive. This can be interpreted either as rain‐out with distance from the west‐northwest ocean source of evaporation or shifts in air mass source with changing North Atlantic Oscillation indices. Applying five U–Th thermal ionisation mass spectrometric (TIMS) dates to a 17.5 cm isotope profile (δ¹⁸O and δ¹³C) along the stalagmite growth axis enabled a tentative interpretation of the palaeoclimate signal over the past 7.1 kyr. Spikes of depleted isotopic δ¹⁸O values are centred near ca. 7, ca. 5.2 and ca. 4 ka, reflecting cool conditions. The record shows two warm intervals between ca. 3.8 and ca. 3.2 ka (the maximum warmth) and from ca. 2 to ca. 1.4 ka, when the δ¹⁸O values were less negative than present. The ‘Holocene Climate Optimum’ spanning the time interval from ca. 6.8 to ca. 4.4 ka is not well expressed in the PU‐2 stalagmite. Individual spikes of lighter δ¹³C are interpreted as indicative of periods of heavy rainfall, at ca. 7, ca. 5.5, and ca. 3.5 ka. The overall trend to lighter δ¹³C in the PU‐2 stalagmite may reflect a gradual decrease in water–rock interaction. The results demonstrate that the effect of North Atlantic oceanic changes extended to the investigated area. Nevertheless, some differences in temporal correlation and intensity of stable isotopic response to these climatic events have been found, but the exact nature of these differences and the underlying mechanism is yet to be determined. Copyright © 2002 John Wiley & Sons, Ltd.     

费-托合成气碳同位素研究

以往认为完整的碳同位素值正序排列是天然气有机成因的特征,完整的反序排列是天然气无机成因的特征。而费-托合成实验的结果中,两种碳同位素值排列都有存在。通过费-托实验基本条件分析与产物同位素特征分析,论证了天然气甲烷同系物碳同位素值正序或反序排列特征是无机合成的必然结果。     

Stable Carbon Isotope Variations in Cave Percolation Waters and their Implications in Four Caves of Guizhou, China

Monitoring and sampling of main plants,soil CO2,soil water,bedrock,spring water,drip water and its corresponding speleothem were performed at four cave systems of Guizhou,Southwest China,from April 2003 to May 2004,in order to understand stable carbon isotope ratios variations of dissolved inorganic Carbon(DIC) in cave percolation waters(δ13CDIC) and their implications for paleoclimate.Stable carbon isotopic compositions and ions(Ca,Mg,Sr,SO4,Cl etc.) were measured for all samples.The results indicate that there are significant differences among the δ13CDIC values from inter-cave,even inter-drip of intra-cave in the four caves.The δ13CDIC values from the Liangfeng Cave(LFC) is lightest among the four caves,where vegetation type overlying the cave is primary forest dominated by tall trees with lighter average δ13C value(–29.9‰).And there are remarkable differences in δ13CDIC values of different drip waters in the Qixing Cave(QXC) and Jiangjun Cave(JJC),up to 6.9‰ and 7.8‰,respectively.Further analyses show that the δ13CDIC values in cave drip waters are not only controlled by vegetation biomass overlying the cave,but also hydro-geochemical processes.Therefore,accurate interpreting of δ13C recorded in speleothems cannot be guaranteed if these effects of the above mentioned factors are not taken into consideration.     

Chemical and boron-isotope variations in tourmalines from an S-type granite and its source rocks: the Erongo granite and tourmalinites in the Damara Belt,Namibia

Tourmaline is widespread in metapelites and pegmatites from the Neoproterozoic Damara Belt, which form the basement and potential source rocks of the Cretaceous Erongo granite. This study traces the B-isotope variations in tourmalines from the basement, from the Erongo granite and from its hydrothermal stage. Tourmalines from the basement are alkali-deficient schorl-dravites, with B-isotope ratios typical for continental crust (δ¹¹B average −8.4‰ ± 1.4, n = 11; one sample at −13‰, n = 2). Virtually all tourmaline in the Erongo granite occurs in distinctive tourmaline-quartz orbicules. This “main-stage” tourmaline is alkali-deficient schorl (20–30% X-site vacancy, Fe/(Fe + Mg) 0.8–1), with uniform B-isotope compositions (δ¹¹B −8.7‰ ± 1.5, n = 49) that are indistinguishable from the basement average, suggesting that boron was derived from anatexis of the local basement rocks with no significant shift in isotopic composition. Secondary, hydrothermal tourmaline in the granite has a bimodal B-isotope distribution with one peak at about −9‰, like the main-stage tourmaline, and a second at −2‰. We propose that the tourmaline-rich orbicules formed late in the crystallization history from an immiscible Na–B–Fe-rich hydrous melt. The massive precipitation of orbicular tourmaline nearly exhausted the melt in boron and the shift of δ¹¹B to −2‰ in secondary tourmaline can be explained by Rayleigh fractionation after about 90% B-depletion in the residual fluid. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

碳酸钙-水体系氧同位素平衡及稳态分馏的低温实验研究

采用“一步”和“两步”的直接沉淀法和附晶生长法在 5 0℃和 70℃分别合成碳钡矿和文石 ,测定不同条件下合成矿物与水之间的氧同位素分馏 ,结果显示 ,文石—水体系氧同位素分馏机理分两步 :(1) [CO3 ]2 - 与H2 O的氧同位素交换和平衡 ,此过程是文石 水氧同位素平衡的决速率步骤 ;(2 )与H2 O平衡以后的 [CO3 ]2 - 与Ca2 +]结合生成文石 ,此过程体现矿物形成过程中氧同位素分馏的结构效应。在此基础上 ,采用缓慢沉淀法和“两步”的附晶生长法获得了 0～ 70℃的文石 水体系氧同位素平衡分馏方程。采用“一步”和“两步”的附晶生长法在 5 0℃和 70℃合成文石 ,文石在溶液中经同质多象转变成次生方解石 ;结合文献数据 ,获得 0～ 70℃范围内的方解石 水体系稳态氧同位素分馏方程。     

塔里木盆地柯坪地区中寒武统准同生白云岩孔洞充填物期次、地化特征及形成条件*

对塔里木盆地柯坪地区蓬莱坝剖面中寒武统沙依里克组萨布哈白云岩及其溶孔中的多期次充填物进行了岩石学和地球化学分析,以对其沉淀时的流体环境进行恢复。孔洞中的环带状充填物可分为4期,由白云岩向内依次为：（1）乳白色粒状方解石;（2）铁质浸染的杂色柱状方解石;（3）无色透明的石英;（4）紫色粒状萤石。碳氧同位素、微量元素及稀土元素分析结果表明：白云岩具有高的Sr/Ba值5.47,低的U/Th值0.2954（明显小于0.7）,高的Zr/Hf值36.86,相对高的稀土总量,相对高的 δ¹⁸O值-7.444‰,盐度指数Z值为120.56,表明它形成于相对低温、富氧和盐度相对较高的流体环境,进一步证实其是形成于蒸发环境的准同生白云岩。第1期方解石具有低的Sr/Ba值2.33,相对高的U/Th值1.3,低的Zr/Hf值20.857,相对居中的稀土总量,相对低的δ¹⁸O值-13.758‰,盐度指数Z值为105.35（小于120）,表明它形成于温度相对较高、缺氧、盐度较低的流体条件下。第2期方解石具有具有相对低的Sr/Ba值2.77,相对高的U/Th值1,相对低的Zr/Hf值32.08,相对居中的稀土总量,相对低的 δ¹⁸O值-11.344‰,盐度指数Z值为116.51,表明其形成于温度相对较高、贫氧、盐度较低的流体条件下。萤石具有居中的Sr/Ba值3.15,相对高的U/Th值0.8666,相对低的Zr/Hf值31.875,相对低的稀土总量,其配分模式与岩浆成因萤石较为接近,表明其形成于温度相对较高、缺氧、低盐度的流体条件下。这些特征反映该套地层经历了准同生期白云岩化后的埋藏-抬升-再埋藏-最终抬升至地表的过程。