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荡子山白榴霓霞岩包体中含有大量的富锶磷灰石.利用电子探针微束分析技术对富锶磷灰石的赋存状态、晶形、矿物共生、成分变化以及成因机制进行了深入细致的研究,发现富锶磷灰石有短柱状和细长柱状两种晶形,并多被其他矿物包裹,表明它们形成于岩浆结晶的早期阶段,其成分为氟磷灰石.之后被富锶流体沿着氟磷灰石颗粒的边缘进行交代,从而形成了富锶磷灰石,交代方式为类质同像置换.富锶磷灰石中SrO含量的变化反映出体系中碱度的变化,体系中的碱度升高时,磷灰石矿物中Sr置换Ca的数量增加,而当体系中的碱度降低时,已经进入到磷灰石矿物晶格中的Na,LREE和Sr离子也会从中分离出来而导致这些阳离子数降低.因此,Sr置换Ca的数量对体系中的碱度变化趋势有着明显的指示意义.根据电子探针成分分析数据计算得出阳离子的个数,富锶磷灰石结构式可写为(Ca3.15～4.963Sr0.019～1.510Ba0.00～0.030Na0.006～0.108REE0.106～0.153)(P2.842～3.028Si0.009～0.094)O12(F0.675～1.079,Cl0.000～0.256,OH–0.084～0.297).利用配有193nm激光的Neptune多接收等离子体质谱仪(LA-MC-ICPMS),对富锶磷灰石原位微区Sr,Nd同位素进行了分析.将分析结果与白榴霓霞岩包体及包体的寄主岩Sr,Nd同位素组成进行了比较,发现交代早期岩浆结晶成因氟磷灰石的富锶流体与白榴霓霞岩包体及包体的寄主岩来自不同的源区,其中,前者来自较亏损地幔,而后两者则来自较富集地幔.
There are a lot of strontium-rich apatite in the Baishan volcanic ash-packed pluton.Using the electron probe microbeam analysis technique, the occurrence state, crystal form, mineralogy, composition change and genetic mechanism of strontium-enriched apatite In-depth and meticulous research, found that strontium-rich apatite has short columnar and elongated columnar two crystal forms, and more than other minerals, indicating that they formed in the early stages of the magma crystallization, the composition of fluorapatite was The strontium-enriched fluid is confronted with the edge of fluorapatite particles, forming a strontium-rich apatite with a homogeneous isomorphous substitution.The variation of SrO content in strontium-rich apatite reflects the alkalinity Changes, the alkalinity in the system increases, the amount of Sr-substituted Ca in the apatite minerals increases, and as the alkalinity in the system decreases, Na, LREE and Sr ions that have entered into the apatite crystal lattice Will also be separated from them resulting in a decrease in the number of these cations, therefore, the number of Ca replacement of the system of alkaline alkalinity trends have obvious indications.According to the electron probe composition analysis data calculated the number of cations, strontium-rich Apatite structural formula can be written as (Ca 3.15 to 4.963Sr0.019 to 1.510Ba0.00 to 0.030Na0.006 to 0.108REE0.106 to 0.153) (P2.842 to 3.028Si0.009 to 0.094) O12 (F0.675 to 1.079, Cl0.000 to 0.256, OH-0.084 ~ 0.297). The Sr, Nd isotopes of Sr-rich apatite in situ were analyzed by Neptune multi-receiver plasma mass spectrometry (LA-MC-ICPMS) The comparison of Sr and Nd isotopic composition of the host rocks of Baimeng Ni-Xia rock inclusions and inclusions revealed that the Sr-Nd isotope composition of the early magmatic genesis and the host rocks of the Baomei Ni-Xia-Xia granulite and its inclusions From different source areas, with the former coming from the more depleted mantle and the latter from the more enriched mantle.