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Oxygen and carbon isotopic composition of carbonate rocks of the Permian Qixia Formation, Sichuan basin: thermal effects of Emeishan Basalt/Composicion isotopica de oxigeno y carbon en rocas de carbonato de la formacion de edad permica Qixia, en la Cuenca de Sichuan: efectos termicos del Basalto Emeishan.

1. Introduction

The Middle Permian Qixia Formation is widely exposed on the margin of the Sichuan Basin. As a typical lithostratigraphic unit of the upper Paleozoic marine strata, this Formation can be used for stratigraphic correlation. The carbonate rocks of the Qixia Formation gradually change from "black Qixia" to "white Qixia" from the east to the west of the Sichuan Basin. The black Qixia is mainly comprised of medium-thick strata of dark grey limestone interbedded with shale and siliceous rocks, and it generally has dark colors and high contents of organic carbon. It is considered to be one of the four sets of marine source rocks in South China (Chen et al., 2010; Lv et al., 2010; Chen et al., 2012; Liu et al., 2014). The white Qixia is comprised of light grey blocks of limestone containing dolomitic limestone and dolomite, and it is mainly distributed throughout the northern sections of the Micang Mountain and the Longmen Mountain (Sichuan Provincial Bureau of Geology and Mineral Resources, 1991). This finding may reduce the significance of the traditional opinion that "the Qixia Formation is black and the Maokou Formation is while" in the case of western Sichuan Basin. For example, the Qixia Formation in the Qiaoting section in Nanjiang area, northeastern Sichuan, is made of overall grey-black limestone strata (Fig. 1a). Moreover, the Qixia Formation in the Changjianggou section in Jian'ge area, northwestern Sichuan, is generally of dark grey limestone, with grey dolomitic limestone forming the upper part (Fig. 1b). It is widely thought that the black Qixia was deposited in a deep water environment while the white Qixia was deposited in shallow water within a carbon platform (Hu et al., 2010; Chen, 2009). Previous work has shown Qixia Formation has the potential to become a hydrocarbon reservoir rock (Zeng et al., 2010; Hao et al., 2013; Tian et al., 2014). Thus, this regional variation of lithological features have elicited strong academic interest for deciphering the nature and development mechanism of this Formation.

Several studies have noticed abundant saddle dolomite and other types of dolomite that are characterized by curved-face and xenomorphic crystals with high homogenization temperatures (max. > 200[degrees]C) were found to be associated with dissolution pores, vugs and factures in the western part of the Sichuan Basin. The impact of geothermal activity has been invoked to explain the dolomitization mechanism (He and Feng, 1996; Wang and Jin, 1997; Chen et al., 2012; Hao et al., 2012; Li et al., 2012; Shu et al., 2012; Huang et al., 2013; Tian et al., 2014). In this paper, we focus on the influence of the related thermal events on the carbon and oxygen isotopic compositions of the marine carbonates of the Qixia Formation.

The global Permian carbonate rocks have stable and relatively high carbon isotopic compositions (Hermann et al., 2010; Saltzman and Thomas, 2012; Laya et al., 2013). In the carbon isotope curve of the Phanerozoic carbonates (Veizer et al., 1999), the central values of [delta][sup.13]C of the Permian rocks were concentrated in the range of 2.5-4.5[per thousand]. In the carbon isotope record of China's Upper Yangtze Permian, which had a higher resolution than that of the curve reported by Veizer et al. (1999), the [delta][sup.13]C values were also mostly in this range (Fig. 2a, Huang, 1997). A decline in [delta][sup.13]C, resulting from extinctions and replacements of life, was found near the Permian-Triassic boundary (Hiete et al., 2013;Tohver et al., 2013), indicating a high content and rapid burial of organic carbon in the global Permian.

[FIGURE 1 OMITTED]

The [delta][sup.18]O values of the global Permian carbonate rocks are mostly in the range of -3~6.5[per thousand], and the corresponding curve is lower than that of the Carboniferous and Triassic (Veizer et al., 1999). This could have occurred because the Permian seawater had a relatively high temperature, or because the thermal events after the depositional stage had an impact on the Permian carbonate rocks. The oxygen isotopic composition of the Upper Yangtze Permian (Huang, 1997) was lower than that of the same period in the curve reported by Veizer et al. (1999). There are two possible reasons for this. One, the samples used by Veizer et al. were more representative of seawater, as carbon isotopes are more easily preserved in carbonates than oxygen isotopes. The other possible reason is that the carbon isotope curve of China's Upper Yangtze Permian had a higher resolution than that of the curve reported by Veizer et al. (1999). As shown in the previously reported curve, the lower [delta][sup.18]O values of the Permian strata from Upper Yangtze were mainly occurred in: (1) the upper part of the Qixia Formation, (2) the top of the Maokou Formation, and (3) the top of the Permian. These three excursion may be associated with the thermal events related to Emeishan basalt eruption, the karstification related to the Dongwu Movement, and the increase in seawater temperature during the late Permian, respectively (Sun et al., 2012).

[FIGURE 2 OMITTED]

Though the curve of carbon isotope in China's Upper Yangtze Permian had a relatively high resolution, only 8 samples of the Qixia Formation were used in the research (Fig. 2a). For further understanding of the composition and variation in carbon and oxygen isotopes in the Qixia Formation, the research group conducted a study on the carbonate rocks of this Formation in two sections, which were located in the northeast and northwest of the Sichuan Basin. A total of 94 groups of carbon and oxygen isotope data were collected and studied through a comparative analysis. Moreover, the impact of the thermal events related to the Emeishan basalt erruption on the carbon and oxygen isotopic compositions of this Formation was discussed.

2. Geological Setting and Sampling

Samples were collected from the Qiaoting section in the northeast of the Sichuan Basin (Nanjiang County) and from the Changjianggou section in the northwest of the basin (Jian-ge County). According to the tectonic division of the Sichuan Basin (Liu et al., 2000), the two sections are parts of the fault zones of the Micang--Daba the Longmen Mountain--Panxi, respectively (Fig. 3). Currently, the linear distance between the two sections is about 130 km in a north-west direction. The initial distance between the sections was supposed to be significantly greater than 130 km, because the tectonic activities following the depositional stage, especially those related to the Himalayan orogeny, could affect the distance between the sections. For instance, the nappe belt on the front edge of the Longmen Mountain, where the Changjianggou section is located, might decrease this distance.

[FIGURE 3 OMITTED]

The Qixia Formation occurs in the western and northern edges of the Sichuan Basin. The triple division of the Permian has been widely used in stratigraphic studies in China and other countries (e.g. Li et al., 2005; Shen et al., 2005). In this paper, the Qixia and Maokou Formations were included in the Middle Permian in accordance with the triple divisions of the Permian marine facies in the Sichuan Basin (Jin et al.,1999; Li et al.,2005) as well as the stratigraphic classification in International Stratigraphic Chart (2008) (Zhang et al., 2009). In these division plans, however, the lower Permian was poorly developed or even absent in Sichuan basin. The lower Permian, comprised of the Liangshan Formation, is about 1m thick in the Changjianggou section and less than 1m in the Qiaoting section. Due to very thin-bedded layers, this Formation was not marked in the maps in this paper.

The large area of Late Paleozoic basalt (Emeishan basalt) sits along the western margin of the Yangtze Block (Huang and Opdyke,1998) and is supposed to have thermal effect on its underlying carbonate rocks. Zhu et al., (2010) has demonstrated that the paleo-heat flow in the west of the Sichuan Basin reached a maximum at the end of the middle Permian at about 259 Ma (Fig. 4a). In this period, the paleo-heat flows measured in most wells were 60-80 mW/[m.sup.2], while the values in a few wells exceeded 100 mW/[m.sup.2]. The paleo-heat flow characteristics reflected the thermal effect of the Emeishan basalt eruption during the late Paleozoic. When the paleo-heat flow peaked, the Permian Qixia Formation was at the shallow burial stage (Fig. 4b).

[FIGURE 4 OMITTED]

3. Methods

Samples used in the carbon and oxygen isotopic analysis were taken from the limestone matrix and dolomite matrix, avoiding the vug--or vein-filling calcite and dolomite crystals. Previous research indicated that the carbon and oxygen isotopic compositions of calcite and dolomite in vugs are lower than those of carbonate matrix (Huang et al., 2014). This research mainly involved the use of some geochemical methods, including carbon and oxygen isotopic analysis, as well as elemental analysis of some samples. The carbon and oxygen isotopic analysis was carried out at Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, and the CNNC Beijing Research Institute of Uranium Geology, with the use of MAT-252 Mass Spectrometry. The latter was responsible for conducting the test in accordance with the standard of Application of Phosphoric Acid Method to the Measurement of Carbon and Oxygen Isotopic Compositions of Carbonate Minerals or Rocks (DZ/T 0184.17-1997). The former was responsible for analyzing the accuracy of the test results using the Kiel IV Carbonate Device sampling system in accordance with the GBW-04405 standard. The standard deviations of the [delta][sup.13]C (PDB) and [delta][sup.18]O (PDB) values were smaller than 0.040 and 0.080, respectively.

The analysis of the contents of CaO, MgO, Mn, Sr, and Fe contents was performed at the Geological and Mineralogical Testing Center of Huayang in Sichuan province. The CaO and MgO contents were measured using normal chemical analysis, with the limit of detection set at 1%. The relative errors of CaO and MgO measurements were 2% and 5%, respectively. The contents of Mn and Sr were determined by atomic absorption spectrometry, with the limits of detection set at 5 x [10.sup.-6] and 42 x [10.sup.-6], respectively. The relative errors of the measurements were 13% and 14%, respectively. The Fe content was determined by colorimetry, with the limit of detection set at 0.01%. The relative error of the result was less than 8%

4. Results and Discussion

Table 1 exhibits the analysis results pertaining to the carbon and oxygen isotopes in 94 carbonate samples from the Qixia Formation in Qiaoting, Nanjiang, and Changjianggou, Jian'ge. The data of 22 samples marked with '[DELTA]' in table 1 have been published by Lv (2013). In addition to the isotopic data, the contents of Ca, Mg, Sr, Mn, and Fe and the corresponding Mn/Sr ratios of 69 of the 94 samples are also given for an understanding of the mineral compositions (relative contents of calcite and dolomite), representativeness, and diagenetic alteration of the samples.

4.1 Elemental compositions and their implication for diagenetic alteration

According to the elemental analysis, the average values of Mn, Fe, and Sr contents in the 69 samples were 48.8 ppm, 729.1 ppm, and 331.5ppm, respectively. Kaufman et al. (1992; 1993) employed Mn/Sr ratio<2~3 as criterion for selecting carbonate samples in which the isotopic values are considered to be proxy for those of seawater. Most of our samples have rather low Mn and Fe contents and relatively high Sr content and the average Mn/Sr ratio was very low, of only 0.31. However, among the aforementioned 69 samples, there were four samples with Mn content higher than 200ppm, having values at 818 ppm, 278 ppm, 406 ppm and 326ppm. Three of these four samples had very high Fe content as well, having values at 10442 ppm, 2724 ppm, and 14987 ppm, corresponding to the first three high Mn values listed above. The curves of carbon and oxygen isotopes in the subsequent discussion indicated that, among the three samples with both high Mn and Fe contents, two samples exhibited very low [delta][sup.13]C and [delta][sup.18]O values, which deviated from the overall trend. These two samples were collected from the bottom of the Qixia Formation in the Qiaoting section, which was adjacent to the Liangshan Formation. It was speculated that these samples were affected by some [sup.12]C--and [sup.16]O-rich fluids that were associated with the clastic rock strata.

The carbonates of the Qixia Formation in the Qiaoting section and the Changjianggou section did not vary substantially in Fe and Mn contents, except for the aforementioned three samples with high Mn and Fe contents. The average Mn contents of the two sections were 47.3 ppm and 52.1 ppm, and their average Fe contents were 322.7 ppm and 344.2 ppm, respectively. The Sr content in the Qixia Formation was significantly higher in the Qiaoting section than in the Changjianggou section. Their average Sr contents were 421.0 ppm and 140.2 ppm, respectively. The Mn/ Sr ratio of the Qixia Formation in the Qiaoting section was 0.05, which is much lower than the ratio of 0.74 in the Changjianggou section. Overall, it can be concluded that geochemical information of these samples are not significantly affected by non-seawater-like fluids such as meteoric fluids, which would lead to enrichment of Mn, Fe and higher Mn/Sr ratio.

4.2 Carbon and oxygen isotopes

Though the carbonates of the Qixia Formation in the two sections did not vary substantially in terms of elemental composition, their carbon and oxygen isotopic compositions varied greatly from one another (Table 1, Fig. 5, and Fig. 6). Selecting the boundary of Carboniferous-Permian and boundary of Qixia and Maokou Formation as joint, by which the [delta][sup.13]C and [delta][sup.18]O profile of sections in this research and previous study could be compiled. The carbon isotopic compositions of carbonates of the Qixia Formation in the Qiaoting section were relatively stable, except for two samples from the bottom that were affected by the clastic rocks of terrigenous origin in the Liangshan Formation. The [delta][sup.13]C values of the samples ranged from 2.7[per thousand] to 5.2[per thousand], with the average being 4.2[per thousand]. This carbon isotopic composition was close to that of the global seawater of the period (Veizer et al., 1999). The high and stable [delta][sup.13]C values of the marine carbonates in the Qixia Formation reflected a good ecological status of the Earth, stable species and populations of marine invertebrates with calcareous shells, and fast and continuous burial of organic carbon during this period.

In contrast, the Qixia Formation in the Changjianggou section exhibited significant variations and negative excursions in [delta][sup.13]C and [delta][sup.18]O records. The [delta][sup.13]C values were between -1[per thousand] and 3.8[per thousand], and the average was 1.5[per thousand], which was significantly lower than that of the Qixia Formation in the Qiaoting section and the global seawater of the same period (Veizer et al., 1999). The low [delta][sup.13]C values were mainly distributed throughout the middle part of the Qixia Formation (the bottom of the second member of the Formation); the [delta][sup.13]C values of samples from this part were mostly between -1[per thousand] and 1[per thousand]. Despite Qixia Formation in the Changjianggou section and Qiaoting section was deposited in a shallow-water platform facies and an open platform facies, respectively (Huang et al., 2004), such difference could not lead to the observed variation in [delta][sup.13]C values due to its insensitive to spatial factor.

It is more difficult to measure the oxygen isotopic compositions of carbonates that can represent seawater in geologic history. In the curve of oxygen isotope in Phanerozoic carbonates reported by Veizer et al. (1999), the oxygen isotopic compositions of marine carbonates showed an overall upward trend over time in the geologic history. In the Qiaoting section, however, the oxygen isotopic compositions of the carbonates of the Qixia Formation were relatively stable overall, ranging from -3.8[per thousand] to 7.8[per thousand] with an average of -5.4[per thousand]. This was slightly lower than that of the global seawater of the same period (Veizer et al., 1999). In contrast, the carbonates of the Qixia Formation in the Changjianggou section showed a significant variation and a negative excursion in oxygen isotopic composition. The [delta][sup.18]O values mostly ranged from -2.1[per thousand] to -9.2[per thousand], and the average was -6.0[per thousand], which is significantly lower than that of both the Qixia Formation in the Qiaoting section and the global seawater of this period reported by Veizer et al. (1999).

[FIGURE 5 OMITTED]

Marine carbonates are the largest inorganic carbon pool in nature. The carbon contents of most diagenetic fluids are relatively low compared to carbonate rock itself, indicating that carbon sources are buffered by the carbonates rather than fluid during diagenesis. As a result, the information about carbon isotope in seawater can be well preserved in carbonate rocks, especially the micritic carbonates that are characterized by low porosity and permeability. Because the possibility of meteoric influence has been ruled out during the sampling and data selecting process, The distinctly low [delta][sup.13]C values of the carbonates of the Qixia Formation in the Changjianggou section indicated that carbon sources with low [delta][sup.13]C values participated in carbonate formation when the rocks still had relatively high porosity and permeability, which lead to high water/rock ratio. Such process could not be involved in the normal thermal evolution of burial diagenesis sequence, because the rock would be highly compacted after high volumes of C[O.sub.2] have been released by the organic matter. In this case, the water/rock ratios were relatively low thus organic carbon's input was not available. Davies (2004) proposed the term "forced maturation" for the alteration of kerogen in host limestones during transient thermal anomalies. Davies and Smith Jr. (2006) pointed out that this process precedes regional burial maturation of organic material. Therefore, we suggested certain unusual thermal events took place in the early stage of diagenesis and caused early forced maturation of organic matter, subsequently decreasing the [delta][sup.13]C values of carbonates by the entrance of carbon sources with low [delta][sup.13]C values. In summary, the lower carbon & isotopic composition of the carbonates of Qixia Formation in the Changjianggou section suggested that the thermal events in the early stage of diagenesis had a greater influence on the Changjianggou section.

[FIGURE 6 OMITTED]

The oxygen isotopic composition of carbonates is quite sensitive to temperature, and the decrease in the [delta]18O values of carbonates is usually caused by isotope fractionation resulting from rising temperature. The lower oxygen isotopic composition of the carbonates of the Qixia Formation in the Changjianggou section suggested that the Qixia Formation in this section had experienced higher temperatures during diagenesis. Due to the influence of the thermal events related to the eruption of the Emeishan basalt, the paleoheat flow in the western Sichuan Basin reached the highest level during the end of the middle Permian. The maximum paleo heat flows experienced by most wells were between 60 and 80 mW/[m.sup.2], and a few wells have exhibited maximum paleo heat flows higher than 100 mW/[m.sup.2] (Zhu et al., 2010). During this period, the Qixia Formation was at the stage of shallow burial (depth=500~100m) (Fig. 1b). The thermal events associated with the Emeishan basalt eruption could reduce the oxygen isotopic composition of the carbonates in the areas affected by the events and cause forced evolution and maturation of the organic matter. This was especially important to the Qixia Formation because of the extremely rapid burial of organic carbon in this Formation. Moreover, the release of C[O.sub.2] by organic carbon sources during the process can further change the carbon isotopic composition of the affected carbonates. Therefore, the Qiaoting section in Nanjiang, which is farther from the basalt area, was less affected by basalt eruption. This could be the major reason for the lower carbon and oxygen isotopic compositions of the carbonates of the Qixia Formation in the Changjianggou section in the west of the Sichuan Basin.

Numerous studies suggest that dolomite formed from seawater would have higher [delta]18O than calcite (eg. Fouke,1994). Several experimental determinations have been carried out for measuring carbonate-water oxygen isotopes fractionation factor and concluded that the fractionation factor of Oxygen will increase during Ca substitution by Mg (eg. Tarutani et al., 1969; Jimenez-Lopez et al., 2004). The rate of change between the [delta][sup.18]O of dolomite and Mg content has been estimated from the difference in [delta][sup.18]O between coprecipitated dolomite and calcite (Vahrenkamp and Swart, 1994). Such estimates for [DELTA][delta][sup.18]Odolo-cal at 25[degrees]C, based on experiments and theoretical calculations, include 4 to 7[per thousand] (Northrop and Clayton, 1966; O'Neil et al., 1969; Matthews and Katz, 1977; Clayton et al., 1989), 2.6 to 4[per thousand] (Fritz and Smith, 1970; Vahrenkamp and Swart, 1994; Schmidt et al., 2005; Vasconcelos et al., 2005;Chacko and Deines, 2008), 3[per thousand] (Land, 1980). Although such values can be translated to 0.05-0.14[per thousand] increase in [delta][sup.18]O per 1%Mg increase, the magnitude of that increase for dolomite is poorly constrained for different temperature condition. Therefore, dolomitization effect are not likely to have significantly contributed to the overall patterns of oxygen isotopic records thus it is not quantified in the current discussion. In addition, given the fact that dolomitization degree in carbonates from Changjianggou section is generally higher than that from Qiaoting section (Li et al., 2015), the difference of temperature effects between these two sections would be higher if we take the effect of A[delta][sup.18]O between dolomite and calcite into account.

The discussion above should lead to the conclusion that, in the areas heavily influenced by the eruption of Emeishan basalt, such as the western part of the Sichuan Basin and some regions in Yunnan and Guizhou Provinces, the organic carbon has experienced forced maturation and oxidation in the early stage of diagenesis due to the thermal effects of the basalt eruption. This might have an adverse impact on hydrocarbon generation in the later stage. Huang and Wang (2008) have noticed that the thermal maturity of bitumen veins in the Kuangshanliang area in Northwestern Sichuan, which is near the Changjianggou section, had high thermal maturities. They proposed that this was caused by thermal alteration and diffusion during deep burial rather than by biodegradation. The thermal events associated with the Emeishan basalt eruption could be another cause of the high thermal maturities of the bitumen veins. Furthermore, the hydrocarbon exploration potential of the areas under the influence of the thermal events may have been reduced due to the early forced maturation and oxidation of organic matter.

5. Conclusions

The marine carbonates of the global Permian Qixia Formation have very high carbon isotopic composition, indicating an ecological prosperous status, and fast and continuous burial of organic carbon during this period. However, Qixia Formation in two sections, the Qiaoting section in the northeast and the Changjianggou section in the northwest of the Sichuan Basin, varied significantly in carbon and oxygen isotopic compositions.

The carbon and oxygen isotopic compositions of the carbonates of the Qixia Formation in the Qiaoting section vary relatively stable; the [delta][sup.13]C values ranged from 2.7[per thousand] to 5.2[per thousand] (mostly around 4[per thousand]), with an average of 4.2[per thousand], and the [delta][sup.18]O values ranged from -3.8[per thousand] to -7.8[per thousand], with an average of -5.4[per thousand]. Both the carbon and oxygen isotopic compositions of the carbonates were close to those of the global seawater of this period.

The carbonates of the Qixia Formation in the Changjianggou section exhibited significant variations and negative excursions in [delta][sup.13]C and [delta][sup.18]O records. The [delta][sup.13]C values were between -1[per thousand] and 3.8[per thousand], and the average was 1.5[per thousand], which is significantly lower than that of the global seawater of the period. The [delta][sup.18]O values were mostly in the -2.1 to -9.2[per thousand] range, and the average was -6.0[per thousand], which is also significantly lower than that of the global seawater of the period.

Most of the carbonate samples from the Changjianggou and Qiaoting sections had very low Mn and Fe contents and a relatively high Sr content. The elemental composition characteristics indicated that the samples from both sections have been diagenetically altered to a small degree and thus were representative of seawater of that period. Therefore, it is unreasonable to attribute the differences between the carbon and isotopic compositions in the two sections of the Qixia Formation to only diagenetic alteration.

The low carbon and oxygen isotopic compositions of the samples from the Changjianggou section were associated with the proximity to the eruption center of the Emeishan basalt. The thermal effect of the related thermal events reduced the oxygen isotopic composition of the carbonates. The high temperature forced the organic matter to mature rapidly, and the C[O.sub.2] released by organic carbon sources during the thermal evolution entered the carbonates, thus resulting in a decline in the [delta][sup.13]C values.

The early forced maturation and oxidation of organic matter may have reduced the hydrocarbon exploration potential of the areas heavily influenced by the eruption of Emeishan basalt, such as western Sichuan Basin and some regions in Yunnan and Guizhou Provinces.

Acknowledgments

This study was supported by the National Natural Science Foundation of China (41272130, 41172099). We also wish to acknowledge the support provided by Key Laboratory for Sedimentary Basin and Oil and Gas Resources of MLR, Grant zdsys2014003 as well as State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Grant PLC201308. In addition, Lv Jie and Lan Yefang are thanked for helpful discussion during field work.

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Huang Keke (1,2), Zhong Yijiang (1,2) *, Li Xiaoning (1,2) and Hu Zuowei (1,2)

(1) State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, CDUT, Chengdu 610059 China

(2) Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China

* Corresponding author. E-mail:zhongyijiang2012@cdut.cn

Record

Manuscript received: 08/08/2015

Accepted for publication: 09/10/2015

How to cite item

doi: http://dx.doi.org/10.15446/esrj.v20n1.52403
Table 1. Carbon and oxygen isotopic compositions of carbonates of
the Qixia Formation in Qiaoting, Nanjiang and Changjianggou,
Jian'ge, and contents of Ca, Mg, Sr, Mn and Fe in the samples and
corresponding Mn/Sr ratio

Changjianggou, Jian'ge, and contents of Ca, Mg, Sr, Mn and Fe in
the samples and corresponding Mn/Sr ratios

Section         Sample No.   Sample type             Thickness (m)

Changjianggou      JG1             limestone               0
Changjianggou      JG6             limestone             3.74
Changjianggou      JG7             limestone             4.37
Changjianggou      JG8             limestone             4.84
Changjianggou      JG9             limestone             5.53
Changjianggou      JG10            limestone             6.22
Changjianggou      JG11            limestone             8.09
Changjianggou      JG12            limestone              9.8
Changjianggou      JG13            limestone             10.8
Changjianggou      JG15            limestone             12.5
Changjianggou      JG16            limestone             13.12
Changjianggou      JG18            limestone             15.98
Changjianggou      JG22            limestone             24.51
Changjianggou      JG23            limestone             27.22
Changjianggou      JG25            limestone             31.57
Changjianggou      JG26      dolomitized limestone       32.66
Changjianggou      JG27            limestone             34.36
Changjianggou      JG28            limestone             35.04
Changjianggou      JG29            limestone             35.76
Changjianggou      JG30            limestone             36.15
Changjianggou      JG31            limestone             38.1
Changjianggou      JG32            limestone             39.49
Changjianggou      JG34            limestone             42.64
Changjianggou      JG35            limestone             43.19
Changjianggou      JG36            limestone             44.58
Changjianggou      JG37            limestone             45.88
Changjianggou     JG39-2           limestone             48.32
Changjianggou      JG41            limestone             49.92
Changjianggou      JG43            limestone             51.58
Changjianggou      JG44            limestone             53.5
Changjianggou     JG45-1           limestone             54.33
Changjianggou      JG47      dolomitized limestone       58.06
Changjianggou      JG48      dolomitized limestone       59.2
Changjianggou      JG49        calcitic dolomite         60.13
Changjianggou      JG50      dolomitized limestone       62.03
Changjianggou     JG51-1     dolomitized limestone       63.29
Changjianggou      JG52        calcitic dolomite         66.57
Changjianggou      JG53      dolomitized limestone       69.09
Changjianggou     JG54-1     dolomitized limestone       69.78
Changjianggou     JG55-1           limestone             72.75
Changjianggou      JG56            limestone             79.06
Changjianggou      JG57      dolomitized limestone       79.95
Changjianggou      JG58            limestone             80.46
Changjianggou      JG59      dolomitized limestone       80.67
Changjianggou      JG60            limestone             82.46
Changjianggou      JG61      dolomitized limestone       83.7
Changjianggou      JG62            limestone             83.7
Qiaoting           LJ-A            limestone             1.67
Qiaoting           LJ-B            limestone             3.35
Qiaoting           LJ-D            limestone             16.74
Qiaoting           LJ-F            limestone             19.69
Qiaoting          LJ-B2            limestone             22.72
Qiaoting          LJ-B4            limestone             24.9
Qiaoting         LJ-B5-1     dolomitized limestone       25.34
Qiaoting          LJ-B6            limestone             25.86
Qiaoting           LJ6             limestone             27.45
Qiaoting          LJ7-1        calcitic dolomite         28.33
Qiaoting           LJ7       dolomitized limestone       28.33
Qiaoting          LJ8A-1           dolomite              28.49
Qiaoting           LJ8A        calcitic dolomite         28.49
Qiaoting           LJ08            limestone             28.49
Qiaoting           LJ09            limestone             28.64
Qiaoting           LJ10            limestone             28.72
Qiaoting           LJ11            limestone             28.92
Qiaoting           LJ12            limestone             29.12
Qiaoting          LJ13-1           dolomite              29.36
Qiaoting           LJ13            limestone             29.36
Qiaoting          LJ14-1           dolomite              31.03
Qiaoting           LJ14            limestone             31.03
Qiaoting          LJ15-1           dolomite              32.23
Qiaoting           LJ15            limestone             32.23
Qiaoting          LJ16-2           dolomite              33.42
Qiaoting           LJ18            limestone             36.42
Qiaoting           LJ20            limestone             37.44
Qiaoting           LJ22            limestone             39.53
Qiaoting           LJ24            limestone             42.86
Qiaoting           LJ26            limestone             44.56
Qiaoting           LJ28            limestone             45.88
Qiaoting           LJ30            limestone             47.6
Qiaoting           LJ32            limestone             48.75
Qiaoting           LJ34            limestone             51.15
Qiaoting          LJ35-1       calcitic dolomite         51.9
Qiaoting           LJ35        calcitic dolomite         51.9
Qiaoting          LJ38-1       calcitic dolomite         53.79
Qiaoting           LJ38        calcitic dolomite         53.79
Qiaoting           LJ41            limestone             57.06
Qiaoting           LJ43            limestone             59.06
Qiaoting           LJ45            limestone             61.38
Qiaoting           LJ46            limestone             66.48
Qiaoting           LJ48            limestone             69.93
Qiaoting           LJ50            limestone             76.37
Qiaoting           LJ51            limestone             78.83
Qiaoting           LJ52            limestone             81.76
Qiaoting          LJ54-1           dolomite              83.98

Section         Sample No.   [delta][sup.13]C     [delta][sup.18]O
PDB ([per thousand])   PDB ([per thousand])

Changjianggou      JG1              -0.48                 -4.08
Changjianggou      JG6               1.4                  -4.4
Changjianggou      JG7               2.2                  -3.7
Changjianggou      JG8               2.3                  -4.7
Changjianggou      JG9               1.9                  -6.2
Changjianggou      JG10              1.9                  -4.1
Changjianggou      JG11              2.7                  -3.58
Changjianggou      JG12              1.4                  -5.9
Changjianggou      JG13              2.4                  -7.7
Changjianggou      JG15              2.9                  -4.8
Changjianggou      JG16              3.3                  -7.1
Changjianggou      JG18              2.8                  -5.1
Changjianggou      JG22             3.84                  -7.22
Changjianggou      JG23              -1                   -6.2
Changjianggou      JG25              0.5                  -6.5
Changjianggou      JG26              1.8                  -4.5
Changjianggou      JG27              0.8                   -6
Changjianggou      JG28              0.3                  -5.9
Changjianggou      JG29              0.9                  -6.5
Changjianggou      JG30              0.7                  -5.9
Changjianggou      JG31              0.1                  -6.6
Changjianggou      JG32             -0.18                 -8.37
Changjianggou      JG34              0.4                   -7
Changjianggou      JG35             -0.66                 -9.11
Changjianggou      JG36             -0.4                  -6.6
Changjianggou      JG37              -1                   -6.7
Changjianggou     JG39-2             0.1                  -7.51
Changjianggou      JG41             -0.4                  -6.6
Changjianggou      JG43             0.16                  -7.03
Changjianggou      JG44              0.7                  -6.5
Changjianggou     JG45-1            0.77                  -7.29
Changjianggou      JG47             2.51                  -6.14
Changjianggou      JG48             2.74                  -6.91
Changjianggou      JG49             1.89                  -9.16
Changjianggou      JG50             2.99                  -6.11
Changjianggou     JG51-1            2.89                  -6.68
Changjianggou      JG52             2.24                  -8.04
Changjianggou      JG53             2.35                   -6
Changjianggou     JG54-1            1.59                  -7.35
Changjianggou     JG55-1            2.06                  -6.2
Changjianggou      JG56             2.09                  -5.42
Changjianggou      JG57             3.28                  -3.96
Changjianggou      JG58             2.05                  -5.72
Changjianggou      JG59             2.41                  -5.04
Changjianggou      JG60             2.78                  -5.37
Changjianggou      JG61              3.3                  -2.1
Changjianggou      JG62               2                   -3.8
Qiaoting           LJ-A             -0.02                 -9.86
Qiaoting           LJ-B             1.67                  -9.11
Qiaoting           LJ-D             2.67                  -7.35
Qiaoting           LJ-F             3.65                  -5.29
Qiaoting          LJ-B2             4.21                  -7.17
Qiaoting          LJ-B4             4.13                  -5.78
Qiaoting         LJ-B5-1            4.12                  -4.58
Qiaoting          LJ-B6             3.71                  -3.65
Qiaoting           LJ6               3.8                  -6.32
Qiaoting          LJ7-1             4.86                  -5.5
Qiaoting           LJ7              4.11                  -7.34
Qiaoting          LJ8A-1            5.22                  -4.27
Qiaoting           LJ8A             4.47                  -6.32
Qiaoting           LJ08             4.16                  -7.5
Qiaoting           LJ09               4                   -7.79
Qiaoting           LJ10             4.19                  -6.33
Qiaoting           LJ11             4.16                  -6.29
Qiaoting           LJ12             4.12                  -6.37
Qiaoting          LJ13-1            4.94                  -4.69
Qiaoting           LJ13             4.14                  -6.67
Qiaoting          LJ14-1            4.47                  -4.44
Qiaoting           LJ14             4.17                  -5.96
Qiaoting          LJ15-1            5.21                  -4.42
Qiaoting           LJ15             4.12                  -5.32
Qiaoting          LJ16-2            4.42                  -6.28
Qiaoting           LJ18               4                   -3.97
Qiaoting           LJ20             4.05                  -5.3
Qiaoting           LJ22             4.17                  -5.04
Qiaoting           LJ24             4.27                  -5.35
Qiaoting           LJ26             4.29                  -5.7
Qiaoting           LJ28             4.42                  -5.32
Qiaoting           LJ30             4.23                  -5.41
Qiaoting           LJ32             4.35                  -4.96
Qiaoting           LJ34             4.36                  -4.47
Qiaoting          LJ35-1            4.62                  -4.81
Qiaoting           LJ35             3.84                  -5.61
Qiaoting          LJ38-1            3.97                  -4.73
Qiaoting           LJ38             3.81                  -4.8
Qiaoting           LJ41             4.39                  -4.58
Qiaoting           LJ43             4.52                  -3.88
Qiaoting           LJ45             4.89                  -4.88
Qiaoting           LJ46             4.84                  -4.78
Qiaoting           LJ48             4.41                  -3.96
Qiaoting           LJ50             4.74                  -5.24
Qiaoting           LJ51             4.83                  -3.79
Qiaoting           LJ52             3.52                  -4.59
Qiaoting          LJ54-1            3.12                  -3.87

Section         Sample No.   CaO (%)   MgO (%)   Sr (ppm)   Mn (ppm)

Changjianggou      JG1        54.91     0.17        84         25
Changjianggou      JG6
Changjianggou      JG7
Changjianggou      JG8
Changjianggou      JG9
Changjianggou      JG10
Changjianggou      JG11       53.84     0.94       279         29
Changjianggou      JG12
Changjianggou      JG13
Changjianggou      JG15
Changjianggou      JG16
Changjianggou      JG18
Changjianggou      JG22       54.08     0.09       553         7
Changjianggou      JG23
Changjianggou      JG25
Changjianggou      JG26
Changjianggou      JG27
Changjianggou      JG28
Changjianggou      JG29
Changjianggou      JG30
Changjianggou      JG31
Changjianggou      JG32        51       3.83        68        102
Changjianggou      JG34
Changjianggou      JG35       54.98     0.39        56         49
Changjianggou      JG36
Changjianggou      JG37
Changjianggou     JG39-2      55.5      0.09        76         32
Changjianggou      JG41
Changjianggou      JG43       55.5      0.26        67         22
Changjianggou      JG44
Changjianggou     JG45-1      55.76     0.13        76         30
Changjianggou      JG47       31.6      5.19        86         64
Changjianggou      JG48       30.93     9.35        28         47
Changjianggou      JG49       29.94     10.89       23         40
Changjianggou      JG50       31.83     9.27        75         49
Changjianggou     JG51-1      31.12     10.29       69        326
Changjianggou      JG52       30.84     11.08      606         70
Changjianggou      JG53       32.78     9.61        68         83
Changjianggou     JG54-1      52.54     8.85       101         38
Changjianggou     JG55-1      55.03     0.26        95         19
Changjianggou      JG56       55.74     0.09       149         20
Changjianggou      JG57       35.66     7.45        92         36
Changjianggou      JG58       55.3      0.35       150         21
Changjianggou      JG59       48.07     6.32       168         23
Changjianggou      JG60       51.14     3.68       117         14
Changjianggou      JG61
Changjianggou      JG62
Qiaoting           LJ-A       49.61      0.4       426        818
Qiaoting           LJ-B       52.96     0.48       1007       278
Qiaoting           LJ-D       54.97     0.32       1206        38
Qiaoting           LJ-F       50.61     3.93       606         15
Qiaoting          LJ-B2       55.63     0.08       308         10
Qiaoting          LJ-B4       55.52     0.08       301         9
Qiaoting         LJ-B5-1      42.23     10.28      823         15
Qiaoting          LJ-B6       54.6      0.99       517         9
Qiaoting           LJ6        55.29     0.25       470         7
Qiaoting          LJ7-1       42.12     16.3       290         13
Qiaoting           LJ7        49.88     4.46       322         7
Qiaoting          LJ8A-1      32.51     19.27      328         13
Qiaoting           LJ8A       36.55     16.19      290         12
Qiaoting           LJ08       53.56     1.82       419         8
Qiaoting           LJ09       54.94     0.33       410         8
Qiaoting           LJ10       54.71     0.74       550         7
Qiaoting           LJ11       55.17     0.33       430         8
Qiaoting           LJ12       55.63     0.08       355         9
Qiaoting          LJ13-1      33.52     18.47      430         32
Qiaoting           LJ13       54.71     0.66       503         9
Qiaoting          LJ14-1      34.97     18.15      382         36
Qiaoting           LJ14       54.25     0.83       474         8
Qiaoting          LJ15-1      32.4      18.23      297         19
Qiaoting           LJ15       55.63     0.08       339         7
Qiaoting          LJ16-2      32.4      18.79      142         20
Qiaoting           LJ18       55.29     0.08       171         8
Qiaoting           LJ20       54.1      0.79       793        406
Qiaoting           LJ22       54.83     0.74       265         11
Qiaoting           LJ24       55.29     0.33       418         15
Qiaoting           LJ26       55.06     0.33       234         7
Qiaoting           LJ28       54.83     0.41       333         10
Qiaoting           LJ30       55.4      0.08       192         9
Qiaoting           LJ32       55.75     0.08       334         10
Qiaoting           LJ34       54.83     0.41       346         9
Qiaoting          LJ35-1      36.87     15.1       214         26
Qiaoting           LJ35        40       13.55      219         28
Qiaoting          LJ38-1      37.99     13.65      377         19
Qiaoting           LJ38       39.77     12.97      234         26
Qiaoting           LJ41       54.6      1.16       321         11
Qiaoting           LJ43       55.29     0.25       366         10
Qiaoting           LJ45       55.52     0.08       523         12
Qiaoting           LJ46       54.71     0.66       857         18
Qiaoting           LJ48       54.48     0.74       382         9
Qiaoting           LJ50       55.63     0.08       462         12
Qiaoting           LJ51       54.83     0.66       381         13
Qiaoting           LJ52       54.25     0.91       346         37
Qiaoting          LJ54-1      32.51     17.26      395        101

Section         Sample No.   Mn/Sr   Fe (ppm)   Remark

Changjianggou      JG1       0.29      1147     [DELTA]
Changjianggou      JG6
Changjianggou      JG7
Changjianggou      JG8
Changjianggou      JG9
Changjianggou      JG10
Changjianggou      JG11       0.1      186      [DELTA]
Changjianggou      JG12
Changjianggou      JG13
Changjianggou      JG15
Changjianggou      JG16
Changjianggou      JG18
Changjianggou      JG22      0.01      202      [DELTA]
Changjianggou      JG23
Changjianggou      JG25
Changjianggou      JG26
Changjianggou      JG27
Changjianggou      JG28
Changjianggou      JG29
Changjianggou      JG30
Changjianggou      JG31
Changjianggou      JG32       1.5      337      [DELTA]
Changjianggou      JG34
Changjianggou      JG35      0.88      135      [DELTA]
Changjianggou      JG36
Changjianggou      JG37
Changjianggou     JG39-2     0.43      186      [DELTA]
Changjianggou      JG41
Changjianggou      JG43      0.33      202      [DELTA]
Changjianggou      JG44
Changjianggou     JG45-1      0.4      354      [DELTA]
Changjianggou      JG47      0.74      152      [DELTA]
Changjianggou      JG48      1.68      261      [DELTA]
Changjianggou      JG49      1.74      337      [DELTA]
Changjianggou      JG50      0.65      455      [DELTA]
Changjianggou     JG51-1     4.72      590      [DELTA]
Changjianggou      JG52      0.12       NG      [DELTA]
Changjianggou      JG53      1.21      253      [DELTA]
Changjianggou     JG54-1     0.38      186      [DELTA]
Changjianggou     JG55-1      0.2      152      [DELTA]
Changjianggou      JG56      0.13      219      [DELTA]
Changjianggou      JG57       0.4      599      [DELTA]
Changjianggou      JG58      0.14      202      [DELTA]
Changjianggou      JG59      0.14      472      [DELTA]
Changjianggou      JG60      0.12      599      [DELTA]
Changjianggou      JG61
Changjianggou      JG62
Qiaoting           LJ-A      1.92     10442        *
Qiaoting           LJ-B      0.28      2724        *
Qiaoting           LJ-D      0.03      374
Qiaoting           LJ-F      0.02      757
Qiaoting          LJ-B2      0.03       92
Qiaoting          LJ-B4      0.03       82
Qiaoting         LJ-B5-1     0.02      983
Qiaoting          LJ-B6      0.02      212
Qiaoting           LJ6       0.02      128
Qiaoting          LJ7-1      0.05      242
Qiaoting           LJ7       0.02      109
Qiaoting          LJ8A-1     0.04      293
Qiaoting           LJ8A      0.04      149
Qiaoting           LJ08      0.02      424
Qiaoting           LJ09      0.02      212
Qiaoting           LJ10      0.01      144
Qiaoting           LJ11      0.02      101
Qiaoting           LJ12      0.02       86
Qiaoting          LJ13-1     0.07      463
Qiaoting           LJ13      0.02      155
Qiaoting          LJ14-1      0.1      677
Qiaoting           LJ14      0.02      143
Qiaoting          LJ15-1     0.06      712
Qiaoting           LJ15      0.02       93
Qiaoting          LJ16-2     0.14      123
Qiaoting           LJ18      0.05       20
Qiaoting           LJ20      0.51     14987        *
Qiaoting           LJ22      0.04      636
Qiaoting           LJ24      0.03      255
Qiaoting           LJ26      0.03       76
Qiaoting           LJ28      0.03      196
Qiaoting           LJ30      0.05      160
Qiaoting           LJ32      0.03      286
Qiaoting           LJ34      0.03      160
Qiaoting          LJ35-1     0.12      602
Qiaoting           LJ35      0.13      309
Qiaoting          LJ38-1     0.05      516
Qiaoting           LJ38      0.11      365
Qiaoting           LJ41      0.03      506
Qiaoting           LJ43      0.03      124
Qiaoting           LJ45      0.02      220
Qiaoting           LJ46      0.02      276
Qiaoting           LJ48      0.02      304
Qiaoting           LJ50      0.03      284
Qiaoting           LJ51      0.03      197
Qiaoting           LJ52      0.11      458
Qiaoting          LJ54-1     0.25      1490

Note: Blank cells in the table represent without detection;
NG=below the limit of detection; 22 samples marked with '[DELTA]'
have been published by Lv, 2013; 3 samples marked with * have
both high Mn content (>200ppm) and high Fe content (>2000ppm).
COPYRIGHT 2016 Universidad Nacional de Colombia, Departamento de Geociencias
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Title Annotation:GEOCHEMISTRY
Author:Keke, Huang; Yijiang, Zhong; Xiaoning, Li; Zuowei, Hu
Publication:Earth Sciences Research Journal
Article Type:Report
Geographic Code:9CHIN
Date:Mar 1, 2016
Words:8631
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