Sulfur Isotope Systematics of Mid-Ocean Ridge Basalts

本研究的目的是评估硫同位素对全球范围内几种大洋中脊玄武岩形成过程的敏感性，并利用硫同位素变化来制约大洋中脊玄武岩及其地幔源区的同化和再循环过程。 硫的稳定同位素（主要是32 S和34 S）在化学蚀变、脱气和岩石-海水相互作用等低温过程中分馏， 不通过高温过程如部分熔融和分级结晶而分级。 因此，MORB中的硫同位素可以作为（1）洋中脊岩浆房同化海水硫和（2）沉积物和洋壳通过上地幔再循环回MORB源区的灵敏示踪剂。 我们 将 使用 高精度 离子 利用微探针测量全球MORB玻璃中原始不混溶硫化物中的硫同位素，以确定MORB中硫同位素的全球变化，并研究这些变化与同化、地壳厚度、扩展速率和热点接近程度的关系。

This proposal is to evaluate the sensitivity of sulfur isotopes to several geologic processes which contribute to the formation of mid-ocean ridge basalts (MORB) on a global scale, and to use sulfur isotope variations to constrain the processes of assimilation and recycling in MORB and their mantle sources. The stable isotopes of sulfur (mainly 32S and 34S) are fractionated by many low-temperature processes such as chemical alteration, degassing and rock-seawater interactions, but are not fractionated by high-temperature processes such as partial melting and fractional crystallization. As a result, sulfur isotopes in MORB can be used as sensitive tracers of (1) assimilation of seawater sulfur in mid-ocean ridge magma chambers, and (2) recycling of sediments and oceanic crust through the upper mantle and back into the source regions of MORB. We will use high-precision ion microprobe measurements of sulfur isotopes in primitive immiscible sulfides from MORB glasses worldwide to define the global variability of sulfur isotopes in MORB, and examine the relationships of these variations to assimilation, crustal thickness, spreading rate, and proximity to hotspots.