The Bear Valley Intrusive Suite (BVIS), located in the southernmost Sierra Nevada Batholith (SNB; California, USA) exposes a transcrustal magma system consisting of lower-crustal gabbros and volumetrically extensive middle- and upper-crustal tonalites. New chemical abrasion–isotope dilution–thermal ionization mass spectrometry U-Pb geochronology shows that the bulk of this ca. 100 Ma magmatic system crystallized in 1.39 ± 0.06 m.y. and was constructed with ultrahigh magmatic fluxes (∼250 km³/km/m.y.). This magmatic flux is roughly a factor of three greater than estimates for the SNB-wide flux during the Late Cretaceous flare-up, showing that individual magmatic systems can be constructed at extremely rapid rates. Further, the Hf isotopic composition of the BVIS (ε_Hfi ∼–2 to +4) only allows for limited (∼25%) crustal assimilation. Our results show that the high magmatic fluxes recorded in the BVIS were dominantly derived from the mantle, and that “flare-up”–like local magmatic fluxes can be produced without extraordinary assimilation of crustal material.

中文翻译：

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高精度地球年代学要求超快速地幔衍生的岩浆通量建立美国加利福尼亚州内华达山脉的跨壳熊谷侵入套件

熊谷侵入套件（BVIS）位于美国内华达山脉的最南端（SNB；美国加利福尼亚州），揭示了一个由下地壳辉长岩和体积较大的中，上地壳同色岩组成的跨地壳岩浆系统。新的化学磨蚀-同位素稀释-热电离质谱U-Pb地球年代学表明，这种化学反应的大部分 100 Ma岩浆系统在1.39±0.06 my处结晶，并以超高岩浆通量（〜250 km ³ / km / my）构造。该岩浆通量大约比白垩纪晚期爆发期间整个SNB范围的通量估计值大三倍，这表明单个岩浆系统可以以极快的速度建造。此外，BVIS的Hf同位素组成（_εHfi〜–2至+4）仅允许有限的（〜25％）地壳同化。我们的结果表明，在BVIS中记录到的高磁通量主要来自地幔，并且在没有异常地壳物质同化的情况下就可以产生“爆发”状的局部磁通量。