Meng, Q.Y.
1*& Yu, Z.C.
11Research Institute of Petroleum Exploration and Development, State Key Laboratory of Enhanced Oil Recovery, China; *mqy5948@petrochina.com.cn
The Yingxiongling area of the Qaidam Basin is the most productive block, which is mainly controlled by the widely distributed limestone reservoir and high-quality salt cap rock. The study area is located in the Cenozoic source rock development area of the Qaidam Basin, and the deep layers have the inherent advantages of near-source. A combination of techniques, such as polarisation microscope, quantitative grain fluorescence (QGF), fluorescence spectroscopy, and microthermometry have been used to characterise the episode of the oil emplacement.
The results show that yellow and light blue fluorescent inclusions are well developed in reservoir. Combined with the burial and thermal history, it is concluded that the deep layers of the Yingxiongling area mainly experienced the low-maturity oil charging in the late Lower Youshashan Formation (15 Ma), and the mature-highly matured oil charging in the late Upper Youshashan Formation (7 Ma). In addition, because of the influence of the late stage of Himalayan tectonic movement, the middle and deep reservoirs have experienced the process of oil charging and migrating to overlying layers.
Fig. 1. Characteristic photomicrographs of oil inclusions in the west (Yingxi) and east (Yingdong) Yingxiongling Area.
Keynote
LA-ICP-MS for fluid inclusion analysis: current capabilities and application cases Mercadier, J.
1*1GeoRessources Lab, CNRS, Université de Lorraine, CREGU, France; *julien.mercadier@univ-lorraine.fr Laser Ablation (LA) coupled to ICP-MS is a
booming technique since the last 25 years in Earth Sciences, with many major contributions concerning the chemical analysis of minerals and fluid inclusions since the pioneer publications by Jackson et al. (1992) and Günther et al. (1998). For the field of fluid inclusions, the application of LA-ICP-MS has currently allowed a deep understanding of the chemistry of geological fluids, whether for the analysis of major (e.g. %) to trace (ppbs) elements, including metals of economic interest (Audétat et al., 1998; Richard et al., 2012;
Richter et al., 2018) and for the measurements of halogens and isotopic ratios to trace geological processes (Leisen et al., 2012, Fusswinkel et al., 2018, Pettke et al., 2004).
Given the possibilities that multiple generations of different fluids of various age and chemistry may be trapped through time in a single mineral phase, the high sensitivity and spatial resolution capabilities of LA-ICP-MS to selectively sample and analyse individual fluid inclusion appeared like a revolution in the understanding of fluid-driven mass transfer in the Earth’s crust. Determining the chemical composition of geological fluids trapped in fluid inclusions by LA-ICP-MS, however, remains currently an analytical challenge. Indeed, fluid inclusions represent micro-cavities of generally 10-100 µm in diametre, which contain small quantities of liquids (pl to nl) with variable compositions and concentrations of chemical elements (Heinrich et al., 2003; Allan et al., 2005; Pettke et al., 2012;
Wagner et al., 2016).
The application of LA-ICP-MS to fluid inclusions generates short transient signals, typically of several seconds. Such a short duration, coupled to the fact that each fluid inclusion can be only analysed once, represents one of the major analytical limits for their analysis by LA-ICP-MS.
This is particularly the case for small fluid inclusions (< 10 µm) and/or containing low-salinity fluid, which in fact represent most of fluid inclusions found in nature compared to the large and high-salinity fluid inclusions encountered in some ore deposits. Such limitations have led to the fact that the detailed chemistry of many geological fluids is not yet known.
Quadrupole (Q) ICP-MS remains today the most widespread technique for the analysis of fluid inclusions due to its high sensitivity, speed, and multi-element capabilities. New developments, like cryo-cell (Albrecht et al., 2014) or triple Q-based ICP-MS configuration coupled to reaction cell, pave the way for new analytical opportunities and detection of elements sensible to isobaric
interferences. Sector-field (SF) and time-of-flight (TOF) ICP-MS have recently proven improvements for fluid inclusion analysis with higher sensitivities, higher speed of acquisition, quasi-simultaneous detection of all elements, and/or lower limits of detection (Wälle and Heinrich 2014; Harlaux et al., 2015). These new generations of ICP-MS reveal to be highly promising for analysing fluid inclusions, but their contribution to the understanding of geological fluids remains largely to be explored.
Some examples based on the use these technologies will be presented to bring new data to this field of research.
Acknowledgement
J.M. thanks researchers and students from GeoRessources lab and Günther Group (ETH Zurich), and TOFWERK, Agilent and Nu.
References
Albrecht M. et al. (2014) J. Anal. Atom. Spectrom.
29:1034-1041.
Allan M.M. et al. (2005) Am. Mineral. 90:1767-1775.
Audétat A. et al. (1998) Science 279: 2091-2094.
Jackson S.E et al. (1992) Can. Mineral 30:1049-1064.
Fusswinkel T. et al. (2018) J. Anal. Atom. Spectrom.
Leisen M. et al. (2012) Chem. Geol. 330-331:197-206.
Pettke T. et al. (2004) Earth Planet. Sc. Lett. 296:267-277.
Pettke T. et al. (2012) Ore Geol. Rev. 44:10-38.
Richard A. et al. (2012) Nat. Geosci. 5:142-146.
Richter L. et al. (2018) Geology 46:263-266.
Wagner T. et al. (2016) Elements 12:323-328.
Wälle M. and Heinrich C. (2014) J. Anal. Atom.
Spectrom. 29:1052-1057.
Initial CO
2content of parental arc magmas of Karymsky volcano (Kamchatka) inferred from study of olivine-hosted melt inclusions
Mironov, N.L.
1*, Portnyagin, M.V.
2,1, Tobelko, D.P.
1, Smirnov, S.Z.
3, Krasheninnikov, S.P.
1& Gurenko, A.
41Vernadsky Institute, GEOKHI RAS, Russia; 2GEOMAR, Germany; 3IGM SB RAS, Russia; 4CRPG, France;
*nmironov@geokhi.ru
We present new data on CO2 content in melt inclusions (MIs) from Karymsky volcano estimated using micro-Raman spectroscopic data on CO2
density of fluid bubbles and volume proportions of glass and fluid inside inclusions (e.g., Moore et al., 2015). This study was focused on further development of this technique, in particular on the ways of simple and precise quantification of 3-D MIs size.
We studied sixteen partially crystallised MIs in olivine (Fo77-89). Before Raman analysis, they were reheated during 5 min at 1170 °C and quenched.
The quenched MIs were consisting of glass and bubbles of vapur-CO2. The bubbles were measured for their density in IGM SB RAS, Novosibirsk, using Horiba LabRam HR800 (532 nm, 1800g). CO2 density ranged from 0.03 to 0.21 g/cm3 (Mironov et al., 2019) (Fig. 1). Sizes of MIs and bubbles were measured using optical methods. MI thickness, which is usually not reported in MI studies, was quantified in two ways.
First, it was measured with built-in microscope micrometre and further corrected for the refractory index of olivine of 1.68 (average value of olivine Fo80-90 refractory indices, e.g. Troeger, 1979).
Independently from the first method, the 3-D size was measured using two orthogonal sections of olivine grains (Fig. 1). Both methods yielded comparable results for the same inclusions. The maximum difference for the estimated relative volume of fluid bubble did not exceed 0.8 %. Based on our measurements, the bubble shows 3.0-5.7 vol%, (4.1 vol% in average) in the MIs (Fig. 1).
None of the MIs has bubble volume exceeding critical value of 6-8% suggested for originally homogeneous MIs (e.g. Aster et al., 2016; Frezzotti et al., 2001).
Based on mass-balance calculation (e.g. Moore et al., 2015; 2018) (Fig. 1), we estimated the minimum CO2 concentrations in the MIs, assuming the presence of CO2 only in the bubbles (Fig. 1) at room-T. The concentrations range from 0.05 to 0.45 wt% and likely represent melts degassed in variable extents and originated from an initial primitive magma enriched in CO2 (≥0.45 wt%).
Note that the using of a less precise estimation for MIs volume (e.g., assuming elongated ellipsoid shape with two equal dimensions) is not accurate in many cases and resulted in highly under- or overestimation of the CO2 content in the MIs (Fig.
1b).
SIMS analyses of CO2 and H2O in the quenched glasses of MIs are currently in progress. The data
will be considered to use to calculate the total amount of CO2 in MIs and show at the meeting to discuss possible crystallisation depths of parental arc magmas and sources of CO2.
Acknowledgement
This work has been supported by Russian Foundation for Basic Research, grant 19-05-00934.
References
Aster E.M. et al. (2016) J. Volcanol. Geoth. Res.
323:148-162.
Frezzotti M.L. (2001) Lithos 55:273-299.
Mironov et al. (2019) Russ. Geol. Geophys+ (submitted).
Moore L.R. et al. (2015) Am. Mineral. 100:806-823.
Moore L.R. et al. (2018) J. Volcanol. Geoth. Res.
358:124-131.
Fig. 1. Minimum CO2 content in Karymsky melt inclusions.
Larger symbols show data for 3D MI/bubble sizes measured optically. The lines indicate CO2 contents in melts obtained by mass-balance calculation (Mironov et al., 2019)