Geochemical Characteristics and Water Content of Melt Inclusions in the Tuff of the Tiaojishan Formation, Liujiang Basin
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摘要:
水作为岩浆体系中最主要的挥发组分，对岩浆的形成和演化有重要的影响，柳江盆地髫髻山组岩浆岩是燕山期火山活动的重要产物，尽管前人对其地球化学特征进行了大量研究，但关于柳江盆地燕山期岩浆中的水含量仍不清楚。熔体包裹体记录了原始岩浆信息，是获取岩浆水含量特征的最直接样品。本文基于全岩地球化学分析，利用标准样品建立了显微激光拉曼光谱定量熔体包裹体水含量的标定曲线，并对柳江盆地髫髻山组下部流纹质岩屑-晶屑凝灰岩中石英斑晶内的原生熔体包裹体进行了水含量定量分析。结果表明：髫髻山组下部凝灰岩样品具有富Si、Al、大离子亲石元素富集、高场强元素亏损、轻稀土富集、重稀土亏损、负Eu异常、Sr含量低等特点；熔体包裹体中水含量的定量分析结果为0.99%～4.98%，平均水含量为2.62%，与前人统计的酸性岩浆水含量基本一致。地球化学特征和熔体包裹体水含量分析结果共同揭示了研究区髫髻山期早期为富水酸性岩浆。结合髫髻山期样品的熔体包裹体水含量测定结果及其早期的大规模火山喷发背景，本文认为岩浆中高含水量增强了岩浆系统的喷发动力，是诱发研究区髫髻山期早期大规模火山爆发的有利因素之一。
要点(1)标定曲线的建立是显微激光拉曼光谱法定量测定熔体包裹体水含量的关键。
(2)熔体包裹体的水含量与拉曼光谱参数之间具有很好的线性关系，应用少量标样即可建立标定曲线。
(3)柳江盆地髫髻山组凝灰岩中熔体包裹体平均水含量为2.62%，属于酸性富水岩浆体系。
HIGHLIGHTS(1) The establishment of a calibration curve is crucial for the quantitative determination of water content in melt inclusions using laser Raman spectroscopy.
(2) The water content of melt inclusions has a strong linear relationship with Raman spectroscopy parameters, allowing a calibration curve to be established with only a few standard samples.
(3) The average water content of melt inclusions in the tuffaceous rocks from the Tiaojishan Formation in the Liujiang Basin is 2.62%, indicating an acidic, water-enriched magmatic system.
Abstract:Water, as the primary volatile component in magmatic systems, has a significant impact on the formation and evolution of magma. The Tiaojishan Formation igneous rocks in the Liujiang Basin are significant products of Yanshanian volcanic activity. Although previous studies have extensively explored their geochemical characteristics, the water content of the magma in the Liujiang Basin during Yanshanian volcanic activity remains unclear. Melt inclusions, which capture the original magmatic information, serve as the most direct samples for determining the water content of magma. Based on geochemical analysis, this study quantitatively determines the water content in melt inclusions using laser Raman spectroscopy with standard samples. The results show that the lower tuff samples of the Tiaojishan Formation are characterized by high Si and Al contents, enrichment in LILEs, depletion in HFSEs, enrichment in LREEs, and depletion in HREEs. The water content in melt inclusions reveals a range of 0.99% to 4.98%, with an average of 2.62%. These characteristics jointly indicate the water-enriched acidic magmatic activity during the early Tiaojishan period in this area. Combining the water content of melt inclusions with the large-scale volcanic eruptions in the stage, this study suggests that high water content in the magma enhanced the eruptive dynamics of the magmatic system, making it a contributing factor to the large-scale volcanic eruption. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202404030074.
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Keywords:
- Liujiang Basin /
- Tiaojishan Formation /
- tuff /
- melt inclusions /
- water content /
- laser Raman spectroscopy
BRIEF REPORTSignificance: Water (H2O) is the most significant volatile component in natural magmatic systems, playing a vital role in shaping the physical and chemical properties of magma. Its presence significantly affects magma viscosity, melting point, and crystallization. Therefore, water exerts a controlling influence over the overall trends of magmatic differentiation and evolution, guiding the chemical evolution of the magma as it cools and solidifies over time[1-3]. Melt inclusions, as snapshots of magma during geological periods, can preserve the original characteristics of the magma, making them the most direct geological samples for assessing water content in magmas[6-8]. Studying the water content in melt inclusions not only reveals the processes of magmatic differentiation and evolution, but also provides critical evidence for understanding the characteristics of magmatic activity.
Despite the importance of water in influencing magmatic processes, current studies on the water content in Mesozoic volcanic rocks, specifically within the Yanshanian Orogen, remain limited. The Tiaojishan Formation volcanics are among the most representative calc-alkaline volcanic rocks of the Mesozoic Yanshanian Orogen, marking the onset of large-scale volcanic eruptions during the Yanshan period[20]. Although extensive research has focused on the geochemistry of these volcanic rocks, the water content within the Tiaojishan Formation’s volcanics is not well-understood[21-25]. This knowledge gap limits our understanding of how water influences magma behavior during large-scale volcanic events of the Yanshan period.
This study addresses the gap by quantifying the water content in melt inclusions from tuff in the Lower Tiaojishan Formation (J2t), an early volcanic product of the Yanshanian Orogen. Utilizing micro-laser Raman spectroscopy, which allows high-resolution, rapid, and non-destructive water content measurement, the study provides quantitative petrochemical data essential for understanding magmatic processes in this region. Our findings advance the understanding of water’s role in regional magmatic differentiation, contributing key insights into the volcanic activity of the Yanshanian Orogen.
Methods: The tuff samples used in this study were collected from the lower part of the Tiaojishan Formation outcrop in the Liujiang Basin, Qinhuangdao, Hebei Province. All experiments were conducted at the National Key Laboratory of Deep Oil and Gas of China University of Petroleum (East China). A Leica DM2700P microscope was used for microscopic observation, while IRIS Intrepid Ⅱ XSP ICP-OES and ELAN9000 ICP-MS were employed for the analysis of major and trace elements. For microscopic laser Raman spectroscopy testing, a LABRAM HR EVO Laser Raman Spectrometer manufactured by HORIBA FRANCE SAS was utilized.
The microscopic laser Raman spectroscopy experiments are conducted with a laser power of 30mW, an integration time of 30s, and each measurement was integrated three times. To enhance the accuracy of the experimental outcomes, the Raman spectra are subjected to a detailed processing procedure. This process involves several critical steps, beginning with intensity correction, which adjusts the spectral data to account for any fluctuations in laser power or detector sensitivity. Following this, baseline correction is applied to remove any background noise or interference, ensuring that the true signal is accurately isolated. Finally, bands integration is performed, where the area under specific peaks within the spectrum is calculated, allowing for a precise quantification of the target components. Acidic silicate glass exhibits a strong LF470 Raman peak height/intensity (Fig.2), and AWF/ALF is preferentially selected as the optimal calibration parameter[11,19]. Subsequently, a crucial calibration curve for water content is established with the glass standards synthesized by Professor Gao Xiaoying’s team from University of Science and Technology of China. Nine well-preserved primary melt inclusions were carefully selected under a microscope for analysis. These inclusions underwent rigorous testing and detailed data processing, during which their water content was meticulously calculated based on the data.
Data and Results: The experimental results obtained by petrographic observation, analysis of major and trace elements and microscopic laser Raman spectroscopy are shown in the following two parts.
(1) Petrological and geochemical characteristics
The tuff from the lower part of the Tiaojishan Formation is classified as Rhyolite lithic-crystalline tuff, characterized by a blocky texture. It predominantly comprises crystal fragments (35%), rock fragments (25%) and matrix (40%). The crystal fragments are mainly composed of quartz and feldspar, with particle sizes reaching up to 1.8mm; The rock fragments consist mainly of rhyolite debris, with particle sizes ranging from 0.5 to 2mm. The matrix is composed of fine dust and volcanic ash.
The major and trace element analysis results of the whole-rock tuff samples are presented in Table 2 and Table 3, respectively. The samples are marked by high concentrations of Si and Al, enrichment in large ion lithophile elements (LILEs), and depletion in high field strength elements (HFSEs) (Fig.4b). The samples also exhibit enrichment in light rare earth elements (LREEs) and depletion in heavy rare earth elements (HREEs) (Fig.4c), along with a negative Eu anomaly and low Sr content. The TAS diagram (Fig.4a) positions the tuff within the rhyolite field, suggesting its formation is closely associated with acidic magmatic activity. The Ta/Yb-Th/Yb diagram (Fig.4d) places the samples within the active continental margin, inferring that the study area was significantly influenced by oceanic subduction and magmatic activity during this period.
(2) Characteristics of melt inclusions and water content in the tuff
The melt inclusions are primarily isolated and randomly distributed within the lattice defects of quartz phenocrysts, indicative of their primary magmatic origin. These inclusions appear colorless or pale yellow, and exhibit a variety of morphologies, including polygonal (Fig.5a, b), ellipsoidal (Fig.5c, d), and oval shapes (Fig.5e), with diameters varying between 30μm and 165μm. Based on their phase characteristics, the melt inclusions can be categorized into three types: (1)glassy+crystalline melt inclusions (Fig.5a), (2)glassy+bubble-bearing melt inclusions (Fig.5b, d), and (3)glassy melt inclusions (Fig.5c, e). The melt inclusions contain either no or only a few small vapor bubbles, indicating their formation in a volcanic facie with a relatively rapid cooling rate[6,43-44].
Water peaks were identified at 3100−3800cm−1; in the nine melt inclusions, with no detection of CO2 or other volatiles (Fig.5f). According to Bowen’s reaction series[45], quartz forms in the late stage of magmatic fractional crystallization, and the composition of melt inclusions captured by quartz closely resembles the pre-eruption magma. In other words, the water content in these melt inclusions reflects the water content in the magma before the eruption[2].
The calibration equation for water content is CH2O=1.26×(AWF/ALF) with R2=0.998 (Fig.3). After processing the micro-laser Raman spectra of the nine melt inclusions, the results (AWF, ALF) are substituted into the water content calibration curve equation [Equation (2)]. Calculations were performed using Excel, and the water content results for the melt inclusions are presented in Table 4. The results indicate that the water content in the melt inclusions within quartz crystal fragments in the tuff from the Tiaojishan Formation in the Liujiang Basin ranges from 0.99% to 4.98%, with an average of 2.62% (Table 4). A comparison with statistical data provided by Li et al.[1] shows that most ultrabasic to basic magmas have a water content ranging from 0 to 0.8%, while intermediate magmas typically range from 0.4% to 2.8%, with an average of 2.26%, and the water content in acidic magmas generally falls between 0.8% and 5.6%, with an average of 2.712%. The high-water content observed in the melt inclusions from the lower Tiaojishan Formation tuff in the Liujiang Basin suggests that the magma transited into an acidic state in the late stage of its evolution.
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土壤矿物中能够被作物直接吸收利用的部分，即有效量，以活动态存在于土壤中[1-2]。元素对环境或生物体产生的效应或毒性，在很大程度上取决于其各形态含量，而不是总浓度[3-4]。土壤微量元素有效量不但影响作物的生长发育，而且影响作物品质和产量[5-8]。因此元素的形态、有效态分析越来越受到研究人员的重视[9-10]。通过土壤有效磷的测定，有助于了解土壤供应磷的情况，为合理使用磷肥及提高磷肥利用率提供依据[11-13]。通常所谓的土壤有效磷是指某一特定形态的磷，只是一个相对指标，但是其可用于说明土壤的供磷水平[14-15]。
目前，测定土壤有效磷的方法主要有Olsen法和Bray法[16]。Olsen法用碳酸氢钠溶液浸提土壤，Bray法用氟化铵-盐酸溶液浸提土壤。方法原理是浸提土壤后，分取浸提液加入显色剂，使用分光光度法测定浸提液中的磷含量。其中Bray法对酸性土壤效果良好，Olsen法对中性及石灰性土壤效果良好[17]。现行标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)和《森林土壤磷的测定》(LY/T 1232—2015)中Olsen法和Bray法的应用存在参数差异[18]，主要差异在于酸性土壤的浸提时间、振荡温度等。目前常用的土壤有效态标准样品中，ASA1-6(GBW07412)、NSA1-6是依据GB/T 7853—1987定值，ASA1a至ASA6a、ASA-7至ASA-10是依据NY/T 1121.7—2006定值(GB/T 7853—1987、NY/T 1121.7—2006分别已被LY/T 1232—2015、NY/T 1121.7—2014替代)。已有文献报道了使用电感耦合等离子体发射光谱法(ICP-OES)测定浸提液中的有效磷[19-22]，由于ICP-OES测定磷的灵敏度低，检出限高，达不到部分土壤样品的有效磷含量，因此分光光度法仍是测定土壤中有效磷的最优选择。该技术存在以下问题：①现有测定方法需浸提后过滤得到澄清待测液，过滤操作繁琐，且有些土壤沉淀颗粒细，极易穿透滤纸，速度慢效率低。②浸提液显色前必须先将pH调至指定值，再加钼锑抗显色剂才能发生特定显色反应。且该方法常使用二硝基酚(变色范围为无色pH 2.4~4.0黄色)作指示剂，由黄色调至恰变浅黄，而土壤浸提液多略带黄色的底色，尤其是有机质含量高的土壤，浸提滤液易呈现黄或褐色[23-25]，导致调pH时颜色无法判断；且二硝基酚属于易制爆试剂，毒性强[26]。
针对以上问题，本文采用离心分离代替过滤；比较了不同浸提时间、不同浸提液酸度、不同酸碱指示剂等实验条件对检测结果的影响；使用溴酚蓝作指示剂调节pH，对比了溴酚蓝指示剂与标准方法的二硝基酚指示剂的检测结果。拟通过对现有方法进行优化创新，提高检测效率。
1. 实验部分
1.1 仪器及工作条件
分光光度计(北京普析通用仪器有限责任公司，型号T9CS)，离心机(天津广丰科技有限公司，型号TD6M)，恒温振荡培养箱(苏州培英实验设备有限公司，型号HZQ-X100)。
1.2 材料和主要试剂
磷标准溶液1000mg/L(国家有色金属及电子材料分析测试中心)。
溴酚蓝指示剂：称取0.20g溴酚蓝溶于100mL乙醇中。
盐酸(北京化学试剂研究所，BⅧ级)；盐酸(国药集团化学试剂有限公司，光谱纯)；氟化铵(Strem Chemicals，ACS)；氟化铵(上海麦克林生化科技有限公司，ACS)。
酸性土壤：土壤有效态成分分析标准样品GBW07416、GBW07412(中国地质科学院地球物理地球化学勘查研究所)；未知样A(野外采集，测定pH < 6.5)。
中性及石灰性土壤：土壤有效态成分分析标准样品GBW07413、GBW07414、GBW07414a(中国地质科学院地球物理地球化学勘查研究所)；未知样B(野外采集，测定pH>6.5)。
其他试剂参考标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)配制，均采用市售分析纯。
1.3 实验条件
参考标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)。
酸性土壤：①待测液的制备：称取酸性土壤5.00g于200mL塑料浸提瓶中，加氟化铵(0.03mol/L)-盐酸(0.025mol/L)浸提液50.0mL，25℃以160r/min恒温振荡60min后，5000r/min离心5min。②移取上清液10mL于50mL比色管中，加入5.00mL硼酸(30g/L)，加水，加入溴酚蓝指示剂2滴，用2mol/L盐酸和2mol/L氨水调节至试液刚呈黄色。③测定：加5.00mL钼锑抗显色剂，定容至50mL，摇匀，25℃以上放置30min后用分光光度计在700nm或880nm处进行吸光度测定，绘制标准曲线，计算出待测样品中有效磷含量。
中性或石灰性土壤：①待测液的制备：称取中性或石灰性土壤2.50g于200mL塑料浸提瓶中，加50.0mL碳酸氢钠浸提液(42g/L)，25℃以160r/min恒温振荡30min后，5000r/min离心5min。②移取上清液10mL于50mL比色管中，加入溴酚蓝指示剂2滴，用0.5mol/L硫酸调节至试液刚呈黄色。③测定：加5.00mL钼锑抗显色剂，定容至50mL，摇匀，25℃以上放置30min后用分光光度计在700nm或880nm处进行吸光度测定，绘制标准曲线，计算出待测样品中有效磷含量。
2. 结果与讨论
2.1 酸性土壤浸提时间及土水比实验结果
用土壤有效态国家标准物质GBW07416开展条件实验，改变酸性土壤浸提时间及水土比，其他条件参考标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)。结果如图 1所示，氟化铵-盐酸偏提取酸性土壤时，随着浸提液比例降低，测定结果降低；随着提取时间增加，提取出的有效磷逐渐减少，与文献报道结果一致。王荣辉等[18]提出，可能是由于土壤体系自身缓冲作用，浸提时间延长，土壤体系pH升高，导致F-对Fe3+和Al3+的配合能力减弱，Fe-P和Al-P的释放量减少而引起。用GBW07416标准物质研究氟化铵-盐酸浸提时间与pH关系，结果如图 2所示，与文献[18]结论一致，且与不同浸提时间的测定结果一致。
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图 1 不同土水比及浸提时间条件下采用氟化铵-盐酸偏提取酸性土壤中有效磷检测结果的比较Figure 1. Comparison of analytical results of available phosphorus in acid soil extracted by NH4F-HCl with different ratio of clay to water and extraction time.![]()
图 2 氟化铵-盐酸浸提时间与pH关系Figure 2. Relationship between extraction time of NH4F-HCl and pH.本实验中使用标准方法的土水比1:10时，需浸提60min，才得到标样值结果。而中性及石灰性土壤可依据标准方法的实验条件测得相应的标样值。
2.2 溴酚蓝指示剂的对比实验
配制标准曲线0、1、5、10、20、30μg/50mL点，并选用国家标准物质GBW07412、GBW07414a、未知土壤样品A、未知土壤样品B及流程空白溶液，调节浸提液pH时分别使用二硝基酚和溴酚蓝作指示剂，用1cm比色池，比较两种方法的吸光度和检测结果。通过比较酸性土壤和中性、石灰性土壤标准曲线点的吸光度，结果表明用这两种指示剂调节pH后，加入显色剂，显色吸光度没有明显差异。表 1是分别用酸性土壤方法、中性和石灰性土壤方法分析对应的土壤未知样、标准物质、空白对比实验结果，可见使用溴酚蓝替代二硝基酚，检测结果完全一致，标准物质结果符合要求，说明本文优化方法可以适用于酸性、中性和石灰性土壤。使用溴酚蓝(变色范围黄色pH 3.0~4.6蓝色)作指示剂调至适宜pH值时颜色为黄色，磷酸根与钼锑抗显色剂形成蓝色配合物，两种颜色波长差异非常大，不干扰后续显色的测定。而且钼锑抗显色剂呈强酸性，加入后不会使待测液pH值向碱性变化而导致溴酚蓝显色剂变色影响实验结果。
表 1 使用不同pH指示剂测定土壤中有效磷结果对比Table 1. Comparison of analytical results of available phosphorus in soil extracted by different pH indicator不同酸碱性土壤 待测液调节pH指示剂 实验样品 吸光度 溶液中有效磷浓度
(μg/50mL)样品中有效磷测定值
(μg/g)有效磷标准值
(μg/g)酸性土壤 二硝基酚 GBW07412 0.245 22.305 22.30 21.2±3.6 未知样A 0.099 8.568 8.57 / 空白溶液 0.009 0.153 / / 溴酚蓝 GBW07412 0.266 23.648 23.65 21.2±3.6 未知样A 0.104 8.458 8.46 / BK 0.006 -0.070 / / 中性或石灰性土壤 二硝基酚 GBW07414a 0.140 14.721 29.44 29±3 未知样B 0.049 6.286 12.57 / 空白溶液 -0.017 0.263 / / 溴酚蓝 GBW07414a 0.116 14.248 28.50 29±3 未知样B 0.024 5.790 11.58 / 空白溶液 -0.020 0.013 / / 由于土壤样品的复杂性，偏提取得到的待测溶液可能含有未知物质，由于偏提取过程中化学反应的复杂性，土壤中的未知物有可能会干扰所用指示剂溴酚蓝的使用效果，但现有方法所用指示剂二硝基酚也存在这种未知性，本方法应用中尚未见不适用情况。
2.3 浸提液pH的影响
标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)中碳酸氢钠浸提液配制后，需用氢氧化钠溶液调节pH至8.5，并定期监测浸提液pH值。选用两个标准物质，配制后直接使用并与调节pH后的浸提液分别测定，有效磷结果见表 2，碳酸氢钠浸提液pH值对结果影响很大，配制后溶液pH为8.22，其浸提检测结果明显偏低。
表 2 碳酸氢钠浸提液pH对有效磷检测结果的影响Table 2. Effect of NaHCO3 extraction with different pH on analytical results of available phosphorus标准物质编号 有效磷测定值(μg/g) 有效磷标准值
(μg/g)未调节pH 调节pH至8.5 GBW07413 14.20 17.49 18.3±2 GBW07414 10.26 12.71 13.8±2.3 氟化铵-盐酸浸提液的pH在标准方法中未作强调，部分文献[27]中偶见pH 1.5~2.0。如2.1章节所述，由于本研究中的浸提时间与行业标准方法《土壤检测第7部分土壤有效磷的测定》(NY/T 1121.7—2014)不一致，且碳酸氢钠碱性浸提液pH对实验结果有主要影响，为了了解酸性浸提液pH的影响程度，实验中尝试用不同厂家的氟化铵及盐酸试剂，按标准方法配制的酸性浸提液pH值为2.7~3.2，测定结果没有明显差异。实验表明将氟化铵-盐酸浸提液pH调节至2后，浸提出大量的磷，明显不适用于有效磷的测定，因此氟化铵-盐酸浸提液配制后可直接使用。实验中发现，氟化铵-盐酸浸提液放置一个月，pH值由2.72略升高至2.79，其浸提GBW07416一小时后溶液pH值为5.04，也比现配的溶液浸提后的pH值(4.90)高。虽检测结果未见明显差异，但浸提液的pH值可能会影响浸提能力，最好每周配制。
以上实验表明，碳酸氢钠浸提液配制后必须调节pH至8.5，氟化铵-盐酸浸提液配制后可直接使用。
2.4 已浸提溶液的存放时间
《森林土壤有效磷的测定》(LY/T 1233—1999)提到浸提后溶液的保存时间，需24h之内测定。本研究测定了两个不同含量水平的酸性土壤样品，结果见表 3，有效磷含量在2μg/g左右的样品，浸提液滤液放置3天检测结果下降约7.57%，放置5天检测结果下降约9.17%；有效磷含量在15μg/g左右的标准样品(GBW07416)，浸提液滤液放置3天检测结果下降约0.43%，放置5天检测结果下降约13.20%。可见浸提液久置后有效磷会损失，其含量下降程度与样品及含量有关，最好在浸提当天完成检测。
表 3 已浸提溶液的存放时间对有效磷检测结果的影响Table 3. Effect of extracted solution with different storage time on analytical results of available phosphorus样品 放置不同时间有效磷测定值(μg/g) 有效磷测定值下降比例(%) 0d 3d 5d 3d 5d 未知样品 2.54 2.34 2.30 -7.57 -9.17 GBW07416 17.05 16.98 14.80 -0.43 -13.20 2.5 方法检出限和精密度
选用酸性土壤有效态标准物质GBW07416和碱性土壤有效态标准物质GBW07414，分别平行偏提取7份，检测结果见表 4。GBW07416检测结果平均值为17.2μg/g，GBW07414检测结果平均值为12.5μg/g，均在标准值范围内，准确度和相对标准偏差符合要求。依据《环境监测分析方法标准制修订技术导则》(HJ 168—2010)附录A.1.2，使用3cm比色皿时，与0.01吸光度对应的浓度值作为检出限，对应曲线浓度点约为0.5μg/50mL。称样量为5.0g分取10mL浸提液时，检出限为0.5μg/g；称样量为2.5g分取10mL浸提液时，检出限为1.0μg/g。
表 4 方法精密度Table 4. Precision tests of the method参数 GBW07416 GBW07414 有效磷测定平均值(μg/g) 17.2 12.5 有效磷标准值(μg/g) 14.8±3.1 13.8±2.3 标准偏差(n=7) 0.5907 0.2323 相对标准偏差(%，n=7) 3.44 1.86 3. 结论
本研究探讨了测定土壤中有效磷标准方法中的实验条件对检测结果的影响，以及酸性土壤浸提时间及土水比对测定结果的影响。结果表明，酸性土壤在1:10土水比条件下，需浸提60min可得到标样值结果，而碱性土壤可依据标准方法实验条件得到标样值结果；同时探讨了浸提液pH的影响，碳酸氢钠浸提液需调pH至8.5，否则结果明显偏低，氟化铵-盐酸浸提液不可调pH且不可久置；对于已浸提溶液的存放时间，最好在浸提当天完成检测。
本研究采用溴酚蓝指示剂替代标准方法的二硝基酚指示剂，标准方法使用的二硝基酚指示剂颜色突变不明显，易受浸提液底色影响，且易制爆、毒性强；而溴酚蓝指示剂调节pH时突变明显，不受浸提液底色干扰，优于标准方法的二硝基酚指示剂。基于两种指示剂的吸光度和检测结果完全一致，表明溴酚蓝指示剂可适用于土壤中有效磷的测定。
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图 2 不同水含量人工合成流纹质玻璃的拉曼光谱
红色实线为5.27% H2O人工合成标准样品的拉曼谱图；橙色实线为4.09% H2O人工合成标准样品的拉曼谱图；绿色实线为2.26% H2O人工合成标准样品的拉曼谱图；蓝色实线为1.48% H2O人工合成标准样品的拉曼谱图。LF-250cm−1～700cm−1为低波段谱带；HF-850cm−1～1300cm−1为高波段谱带；WF-3000cm−1～3800cm−1为总水谱带。
Figure 2. Raman spectra of artificially synthesized rhyolitic glasses with different water content
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图 3 含水流纹质玻璃水含量标定曲线
Figure 3. Calibration curve for total water content in hydrous rhyolitic glasses
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图 5 熔体包裹体镜下照片及熔体包裹体显微激光拉曼光谱图
a为玻璃质+结晶质熔体包裹体；b、d、g、h为玻璃质+气泡熔体包裹体；c、e、f为玻璃质熔体包裹体；i为熔体包裹体MI-1减基线后的拉曼光谱图。
Figure 5. Microscopic photos showing characteristics of the melt inclusions and Raman spectrum of the melt inclusions
表 1 不同水含量人工合成含水硅酸盐玻璃标准样品的积分面积等参数测量结果
Table 1 Measurement results of integrated area and other parameters of artificially synthesized water-containing silicate glasses standard samples with different water content
人工合成含水玻璃
标准样品编号ALF AWF AWF/ALF*
(Tu等［19］测量值)AWF/ALF
(转换值或实测值)CH2O
(%)RH-1(Tu等，2023) / / 1.0700 0.3726 0.33 RH-2(Tu等，2023) / / 1.3300 0.4631 0.41 RH-3(Tu等，2023) / / 1.8400 0.6407 0.58 RH-4(Tu等，2023) / / 3.2600 1.1351 1.48 RH-5(Tu等，2023) / / 4.9400 1.7201 2.26 RH-6(Tu等，2023) / / 6.3100 2.1971 3.01 RH-7(Tu等，2023) / / 8.5100 2.9632 4.09 RH-8(Tu等，2023) / / 11.7800 4.1018 5.27 RH-9(Tu等，2023) / / 14.3000 4.9793 6.35 RH-10(Tu等，2023) / / 15.4400 5.3762 6.84 RH-11(Tu等，2023) / / 21.3100 7.4201 9.05 标准样品1 292.6424 1264.846 / 4.3222 5.27 标准样品2 244.9186 776.2908 / 3.1696 4.09 标准样品3 229.9241 374.9651 / 1.6308 2.26 标准样品4 189.5898 250.3734 / 1.3206 1.48 注：RH-1至RH-11为Tu等［19］测试样品；标样1至标样4为本文中的实际测试样品，分别对应Tu等［19］的样品RH-8、RH-7、RH-5、RH-4。“/”代表本文未使用的数据。 
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表 2 髫髻山组凝灰岩全岩主量元素测试结果
Table 2 Analytical results of major elements in tuff of the Tiaojishan Formation
凝灰岩样品
编号Na2O
(%)MgO
(%)Al2O3
(%)SiO2
(%)P2O5
(%)K2O
(%)CaO
(%)TiO2
(%)MnO
(%)Fe2O3
(%)烧失量
(%)Na2O+K2O
(%)主量元素含量
合计(%)TJS-1 1.45 1.29 13.02 75.18 0.03 2.60 1.10 0.14 0.04 2.28 3.38 4.04 100.48 TJS-2 1.67 0.65 12.61 77.14 0.02 2.58 0.14 0.14 0.03 1.06 3.04 4.24 99.07 注：为确保测试结果的可靠性，实验数据取同一样品两次测试结果的平均值。
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表 3 髫髻山组凝灰岩全岩微量元素测试结果
Table 3 Analytical results of trace elements in tuff of the Tiaojishan Formation
凝灰岩样品
编号Li
(μg/g)Be
(μg/g)B
(μg/g)Sc
(μg/g)V
(μg/g)Cr
(μg/g)Co
(μg/g)Ni
(μg/g)Cu
(μg/g)Zn
(μg/g)Ga
(μg/g)Ge
(μg/g)As
(μg/g)Rb
(μg/g)Sr
(μg/g)TJS-1 29.75 4.72 17.15 3.84 6.09 7.14 1.26 3.90 2.57 36.30 19.25 1.68 0.41 76.35 139.50 TJS-2 10.46 3.78 15.55 4.89 6.59 4.43 0.72 1.69 2.39 18.56 17.55 0.80 0.47 74.13 97.87 凝灰岩样品
编号Y
(μg/g)Zr
(μg/g)Nb
(μg/g)Mo
(μg/g)Cd
(μg/g)Cs
(μg/g)Ba
(μg/g)La
(μg/g)Ce
(μg/g)Pr
(μg/g)Nd
(μg/g)Sm
(μg/g)Eu
(μg/g)Gd
(μg/g)Tb
(μg/g)TJS-1 16.75 112.50 26.30 2.24 0.09 1.39 451.50 32.45 63.90 7.16 23.90 4.84 0.31 4.04 0.61 TJS-2 13.50 100.77 27.64 1.80 0.04 0.99 386.05 24.29 52.86 5.53 17.92 3.56 0.24 2.80 0.45 凝灰岩样品
编号Dy
(μg/g)Ho
(μg/g)Er
(μg/g)Tm
(μg/g)Yb
(μg/g)Lu
(μg/g)Hf
(μg/g)Ta
(μg/g)W
(μg/g)Tl
(μg/g)Pb
(μg/g)Bi
(μg/g)Th
(μg/g)U
(μg/g)TJS-1 2.95 0.63 1.65 0.27 1.91 0.31 3.97 2.02 0.51 0.63 24.40 0.16 22.40 6.35 TJS-2 2.45 0.50 1.44 0.25 1.70 0.27 3.68 2.04 0.70 0.60 20.70 0.10 21.60 5.50 注：为确保测试结果的可靠性，实验数据取同一样品两次测试结果的平均值。
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表 4 髫髻山组凝灰岩中熔体包裹体LF、WF积分面积及水含量计算结果
Table 4 Integrated areas of LF and WF, and water content of the melt inclusions in tuff of the Tiaojishan Formation
包裹体样品编号 熔体包裹体类型 ALF AWF AWF/ALF 峰位(cm−1) CH2Ot (%) MI-1 玻璃质 120.2732 203.0257 1.6880 3631 2.13 MI-2 玻璃质 119.9589 208.9559 1.7419 3631 2.19 MI-3 玻璃质 297.2329 233.0028 0.7839 3643 0.99 MI-4 玻璃质 198.5294 276.1755 1.3911 3636 1.75 MI-5 玻璃质 180.3690 306.9109 1.7016 3631 2.14 MI-6 玻璃质+气泡 78.6287 288.6345 3.6709 3636 4.63 MI-7 玻璃质+气泡 222.9093 237.9510 1.0675 3637 1.35 MI-8 玻璃质+气泡 526.2989 1446.2396 2.7479 3541 3.46 MI-9 玻璃质+结晶质 186.4130 737.1156 3.9542 3568 4.98
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