Convergent plate boundaries are key sites for continental crustal formation and recycling. Quantifying the evolution of crustal thickness and paleoelevation along ancient convergent margins represents a major goal in orogenic system analyses. Chemical and in some cases isotopic compositions of igneous rocks formed in modern supra-subduction arcs and collisional belts are sensitive to Moho depths at the location of magmatism, implying that igneous suites from fossil orogens carry information about crustal thickness from the time they formed. Several whole-rock chemical parameters correlate with crustal thickness, some of which were calibrated to serve as “mohometers,” that is, quantitative proxies of paleo-Moho depths. Based on mineral-melt partition coefficients, this concept has been extended to detrital zircons, such that combined chemical and geochronological information extracted from these minerals allows us to reconstruct the crustal thickness evolution using the detrital archive. We discuss here the mohometric potential of a variety of chemical and isotopic parameters and show that their combined usage improves paleocrustal thickness estimates. Using a MATLAB^® app developed for the underlying computations, we present examples from the modern and the deeper time geologic record to illustrate the promises and pitfalls of the technique. Since arcs are in isostatic equilibrium, mohometers are useful in reconstructing orogenic paleoelevation as well. Our analysis suggests that many global-scale correlations between magma composition and crustal thickness used in mohometry originate in the sub-arc mantle; additional effects resulting from intracrustal igneous differentiation depend on the compatible or incompatible behavior of the involved parameters.

中文翻译：

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化学测势法：利用地球化学和同位素数据评估古代造山带的地壳厚度


汇聚板块边界是大陆地壳形成和再循环的关键场所。量化沿古代汇聚边缘的地壳厚度和古海拔的演化是造山系统分析的一个主要目标。现代超俯冲弧和碰撞带中形成的火成岩的化学成分和某些情况下的同位素成分对岩浆活动位置的莫霍面深度敏感，这意味着来自化石造山带的火成岩套携带了有关地壳形成时的地壳厚度的信息。一些全岩化学参数与地壳厚度相关，其中一些经过校准可用作“莫霍米”，即古莫霍面深度的定量代表。基于矿物熔体分配系数，这一概念已扩展到碎屑锆石，这样，从这些矿物中提取的化学和地质年代信息相结合，使我们能够利用碎屑档案重建地壳厚度演化。我们在这里讨论各种化学和同位素参数的莫氏势，并表明它们的组合使用可以改善古地壳厚度的估计。使用为底层计算开发的 MATLAB ^®应用程序，我们提供了现代和更深层的地质记录中的示例，以说明该技术的前景和缺陷。由于弧处于均衡状态，莫温计也可用于重建造山带古海拔。我们的分析表明，莫氏测量中使用的岩浆成分和地壳厚度之间的许多全球尺度的相关性起源于弧下地幔。地壳内火成岩分异所产生的额外影响取决于所涉及参数的相容或不相容行为。