The Oligocene Latir magmatic center in northern New Mexico is an exceptionally well exposed volcano-plutonic complex that hosts a variety of magmatic-hydrothermal deposits, ranging from relatively deep, F-rich porphyry Mo mineralization to shallower epithermal deposits. We present new whole-rock chemical and isotopic data for plutonic rocks from the Latir magmatic center, including extensive sampling of drill core samples of intrusive rocks from the Questa porphyry Mo deposit. These data document temporal chemical trends of porphyry-related mineralization that occurred after caldera-forming magmatism and during postcaldera batholith assembly. Silicic magmas were generated multiple times throughout the history of the Latir magmatic center, but few are associated with the formation of a mineral deposit. Whole-rock trace element ratios and Sr, Nd, and Pb isotope compositions vary throughout the protracted history of silicic magmatism. The caldera-forming ignimbrite and early phase of postcaldera intrusions are unmineralized, more enriched in high field strength elements, and generally contain less radiogenic Sr and Pb and more radiogenic Nd than later intrusions. The Questa porphyry Mo deposit formed immediately after the most isotopically primitive phase of the batholith was assembled, ruling out simple reworking of juvenile mantle-derived crust as the source for mineralizing magmas. Rhyolite dikes associated with polymetallic sulfide deposits intruded ~800 k.y. after Mo mineralization, and Nd isotope data indicate that these dikes are associated with different batches of magma and are unrelated to the Mo-mineralizing intrusions at the Questa mine. Together, these data indicate that the source of magmas changed significantly throughout the 10-m.y. history of the magmatic center. We assess multiple genetic models for porphyry-related magmatism against this data set, favoring models with discrete periods of magma genesis from a deep hybridized zone in the lower crust giving rise to the punctuated periods of mineralization. These observations suggest that the formation of mineral deposits within a central magmatic locus is likely the result of the piecemeal assembly of individual hydrothermal-magmatic systems, and that distal and younger polymetallic mineralization commonly observed near known porphyry deposits represents decoupled processes.

中文翻译：

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美国新墨西哥州 Questa Mo 斑岩矿床及附近多金属矿化的成因

新墨西哥州北部的渐新世拉提尔岩浆中心是一个暴露程度极高的火山-深成杂岩体，蕴藏着各种岩浆-热液矿床，从相对较深的富氟斑岩钼矿化到较浅的浅热液矿床。我们提供了来自 Latir 岩浆中心的深成岩的新全岩化学和同位素数据，包括来自 Questa 斑岩钼矿床的侵入岩钻芯样本的广泛采样。这些数据记录了火山口形成岩浆作用之后和火山口后岩基组装期间发生的与斑岩相关的矿化的时间化学趋势。在拉提尔岩浆中心的历史上，硅质岩浆曾多次生成，但很少与矿床的形成有关。在硅质岩浆作用的漫长历史中，全岩微量元素比例以及 Sr、Nd 和 Pb 同位素组成不断变化。破火山口形成的熔结岩和破火山口后侵入体的早期阶段是未矿化的，高场强元素更富集，并且通常比后来的侵入体含有更少的放射性Sr和Pb以及更多的放射性Nd。奎斯塔斑岩钼矿床是在岩基同位素含量最高的原始相聚集后立即形成的，排除了新生地幔地壳的简单改造作为​​矿化岩浆来源的可能性。与多金属硫化物矿床相关的流纹岩脉在钼成矿后侵入~800 ky，Nd同位素数据表明这些脉体与不同批次的岩浆伴生，与Questa矿的钼成矿侵入无关。总之，这些数据表明，在岩浆中心的 10 多年历史中，岩浆来源发生了显着变化。我们根据该数据集评估了与斑岩相关的岩浆作用的多种遗传模型，倾向于采用下地壳深层混合带岩浆成因的离散周期模型，从而产生间断的矿化周期。这些观察结果表明，中央岩浆场所内矿床的形成可能是各个热液-岩浆系统零碎组合的结果，而在已知斑岩矿床附近常见的远端和较年轻的多金属矿化代表了脱钩过程。