关键词: 锶同位素, 地层学, 分步淋洗, 热电离质谱仪（TIMS）, 多接收电感耦合等离子体质谱仪（MC-ICP-MS）, 海相
碳酸盐岩, 样品前处理, 牡蛎化学成分

Abstract: Strontium Isotope Stratigraphy (SIS) is an important tool for establishing age models for oceanic sedimentary deposits. It has wide applications in many fields including oil and gas exploration and paleoclimate reconstructions. SIS is based on the
premise that global seawater is homogeneous relative to Sr isotopes but with variations through time. A key assumption of SIS is that the samples retain the Sr isotope composition of the original seawater where they form. However, diagenesis and loosely attached impurities can alter the Sr isotope composition of the fossil samples, thereby undermining the meaningfulness of the SIS age. Therefore, sample selection and preparation are crucial for obtaining meaningful SIS ages. This article evaluates existing methods for SIS, including sample preparation and Sr isotope analysis. In recent years, to precisely extract the composition of ancient seawater, studies using Nd, Pb, and Li isotopes in carbonates have thoroughly investigated different methods of sample preparation. Based on these technical advances, this paper thoroughly investigated an oyster sample with independent age constraints from the Miocene shallow-marine deposits of the Gulf of Suez, Egypt. By comparing the elemental composition of sequential leachates of the oyster with those of present-day organisms, this paper proposes a new protocol for SIS sample preparation. This paper also compiles and compares the accuracy and precision of Sr isotope data measured using Thermo-ionizing mass spectrometry (TIMS) vs. Multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). While for samples with abundant Sr, the new generation of MC-ICP-MS can reach similar precision and accuracy as the old generation TIMS, for smaller samples and samples that require higher precision, the new generation TIMS is still the best choice for SIS research. Finally, this paper makes some suggestions for Sr analysis on the MC-ICP-MS. 

Key words: strontium isotope, stratigraphy, sequential leaching, Thermo-Ionizing Mass Spectrometry (TIMS), Multi-Collector
Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS), marine carbonate, oyster chemistry, sample preparation