Monazite geochronology and geochemistry of meta-sediments in the Narryer Gneiss Complex, Western Australia: constraints on the tectonothermal history and provenance
Monazite geochronology and geochemistry of meta-sediments in the Narryer Gneiss Complex, Western Australia: constraints on the tectonothermal history and provenance
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DOI：
10.1007/s00410-010-0508-0
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发表时间：
2010-03
影响因子：
3.5
通讯作者：
T. Iizuka;M. McCulloch;T. Komiya;T. Shibuya;K. Ohta;Haruka Ozawa;E. Sugimura;K. Collerson
中科院分区：
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作者：
T. Iizuka;M. McCulloch;T. Komiya;T. Shibuya;K. Ohta;Haruka Ozawa;E. Sugimura;K. Collerson
西澳大利亚州伊尔加恩克拉通的纳里尔片麻岩杂岩中的纳里尔山和杰克山变质沉积岩特别重要，因为它们产出冥宙碎屑锆石。为了更好地了解这些古代沉积物的构造热历史和来源，我们整合了变沉积物中独居石的背散射扫描电子图像、原位 U-Pb 同位素和地球化学数据。数据表明，在构造热事件期间，纳里尔山变质沉积物中存在多个变质独居石生长时期，包括~3.3-3.2 和 2.7-2.6 Ga 的变质作用。这些结果为纳里尔山沉积物的沉积设定了 3.2 Ga 的新最小年龄，之前限制在 3.28 至~2.7 Ga 之间。随着独居石的生长，在富含 Fe 和 Mn 的样品中存在相对较高比例的碎屑独居石。这可能是因为高铁和锰的整体成分导致石榴石有效屏蔽早期形成的独居石。在杰克山变质沉积物中，变质独居石生长较小，表明序列中不存在高级变质作用。碎屑独居石为纳里尔山沉积物的起源提供了证据。 3.6 和 3.3 Ga 花岗岩，可能对应于纳里尔片麻岩杂岩中的 Meeberrie 和 Dugel 花岗片麻岩。尚未发现年龄超过3.65 Ga的独居石，这意味着沉积物中>3.65 Ga碎屑锆石的源岩中几乎不含独居石，或者>3.65 Ga碎屑矿物经历了显着的变质事件或长期的沉积循环，导致独居石完全溶解或重结晶。
Mt. Narryer and Jack Hills meta-sedimentary rocks in the Narryer Gneiss Complex of the Yilgarn Craton, Western Australia are of particular importance because they yield Hadean detrital zircons. To better understand the tectonothermal history and provenance of these ancient sediments, we have integrated backscattered scanning electron images, in situ U–Pb isotopic and geochemical data for monazites from the meta-sediments. The data indicate multiple periods of metamorphic monazite growth in the Mt. Narryer meta-sediments during tectonothermal events, including metamorphism at ~3.3–3.2 and 2.7–2.6 Ga. These results set a new minimum age of 3.2 Ga for deposition of the Mt. Narryer sediments, previously constrained between 3.28 and ~2.7 Ga. Despite the significant metamorphic monazite growth, a relatively high proportion of detrital monazite survives in a Fe- and Mn-rich sample. This is likely because the high Fe and Mn bulk composition resulted in the efficient shielding of early formed monazite by garnet. In the Jack Hills meta-sediments, metamorphic monazite growth was minor, suggesting the absence of high-grade metamorphism in the sequence. The detrital monazites provide evidence for the derivation of Mt. Narryer sediments from ca. 3.6 and 3.3 Ga granites, likely corresponding to Meeberrie and Dugel granitic gneisses in the Narryer Gneiss Complex. No monazites older than 3.65 Ga have been identified, implying either that the source rocks of >3.65 Ga detrital zircons in the sediments contained little monazite, or that >3.65 Ga detrital minerals had experienced significant metamorphic events or prolonged sedimentary recycling, resulting in the complete dissolution or recrystallization of monazite.