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首页> 外文期刊>Contributions to Mineralogy and Petrology >Formation by silicate-fluoride plus phosphate melt immiscibility of REE-rich globular segregations within aplite dikes
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Formation by silicate-fluoride plus phosphate melt immiscibility of REE-rich globular segregations within aplite dikes

机译：通过硅酸盐和磷酸盐熔体的形成不混溶在荷丝特堤坝内富含REE的球状偏见

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摘要

Aplite dikes intruding the Proterozoic 1.42(+/- 3) Ga Longs Peak-St. Vrain Silver Plume-type peraluminous granite near Jamestown, Colorado, contain F, P, and rare earth element (REE)-rich globular segregations, with 40-46% REE, 3.7-4.8 wt% P2O5, and 5-8 wt% F. A combination of textural features and geochemical data suggest that the aplite and REE-rich globular segregations co-existed as two co-genetic liquids prior to their crystallization, and we propose that they are formed by silicate-fluoride + phosphate (+S+CO2 ) melt immiscibility following ascent, cooling, and decompression of what was initially a single homogeneous magma that intruded the granite. The REE distribution coefficients between the silica-rich aplites and REE-rich segregations are in good agreement with experimentally determined distribution coefficients for immiscible silicate-fluoride +phosphate melts. Although monazite-(Ce) and uraninite U-Th-Pb microprobe ages for the segregations yield 1.420(+/- 25) and 1.442(+/- 8) Ga, respectively, thus suggesting a co-genetic relationship with their host granite, (epsilon)(Ndl.42Ga) values for the granites and related granitic pegmatites range from -3.3 to -4.7 (average - 3.9), and differ from the values for both the aplites and REE-rich segregations, which range from -1.0 to -2.2 (average -1.6). Furthermore, the granites and pegmatites have (La/Yb)(N) 50 with significant negative Eu anomalies, which contrast with higher (La/Yb)(N) 100 and absence of an Eu anomaly in both the aplites and segregations. These data are consistent with the aplite dikes and the REE-rich segregations they contain being co-genetic, but derived from a source different from that of the granite. The higher ENdl 42Ga values for the aplites and REE-rich segregations suggest that the magma from which they separated had a more mafic and deeper, dryer and hotter source in the lower crust or upper mantle compared to the quartzo-feldspathic upper crustal source proposed for the Longs Peak-St. Vrain granite.
机译：Aplite Dikes侵入前果古代1.42（+/- 3）Ga Longs Peak-ST。贾姆斯敦，科罗拉多州，含有F，P和稀土元素（REE） - 稀土元素（REE） - 中间的脉冲花岗岩（REE），含有40-46％的REE，3.7-4.8wt％p2o5和5-8wt％f 。纹理特征和地球化学数据的组合表明，在结晶前，富含富含富含的富含热团状的球状偏析作为两个共遗传液体，并且我们提出它们通过硅酸盐+磷酸盐形成（+ S +二氧化碳）在上升，冷却和减压之后熔化不混溶，最初是初始均匀岩浆的侵入花岗岩。富含二氧化硅的消耗和REE的偏析之间的REE分布系数与用于不混溶的硅酸盐+磷酸盐熔体的实验确定的分布系数良好。虽然单一 - （Ce）和铀酸盐岩U-TH-PB微探针分别为偏析产量1.420（+/- 25）和1.442（+/- 8）GA，因此表明与其主机花岗岩的共遗传关系， （ε42ga）花岗岩的值（Nd1.42ga）花岗岩的值和相关的花岗岩PEGMATITE的值范围为-3.3至-4.7（平均-3.9），与富含消耗和富含再培养的分离的值不同，范围为-1.0至-2.2（平均-1.6）。此外，花岗岩和pegmatites具有（La / Yb）（n）＆ 50具有显着的阴性欧盟异常，其与更高（la / yb）（n）＆ 100并在两种牌中没有欧盟异常的情况隔离。这些数据与Aplite堤防和它们含有共同遗传的富含浓度的分离一致，但是来自不同于花岗岩的源。富含塞特和富含钢筋的分离的较高的Endl 42Ga值表明，与Quartzo-FeldPaththatht的上层地壳源相比，它们分开的岩浆在下部地壳或上部地幔中具有更具猛秀和更深的，干燥器和较热的源龙峰峰-T。 vrain花岗岩。

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