One size does not fit all: Refining zircon provenance interpretations via integrated grain shape, geochronology, and Hf isotope analysis

IF 8.5 1区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Gisela Gartmair, Milo Barham, Christopher L. Kirkland
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引用次数: 2

Abstract

Sediment provenance studies commonly utilize isotopic signatures to resolve detrital mineral sources and routing. However, non-unique ages and geochemical characteristics across geographically distinct crystalline source regions can lead to significant ambiguities in mineral provenance interpretations. Such ambiguity is apparent in southern Australia’s Cenozoic Eucla Basin, which hosts world-class heavy mineral sand resources. Here, new Hf isotope data are provided from four heavy mineral prospects (N = 8, n = 844 [N = samples, n = grains]). Zircon grain shape data are also presented for a suite of detrital Eucla Basin samples (N = 22, n = 35,604) and the basin’s underlying basement, the Coompana Province (N = 13, n = 824). The data are integrated with published detrital and non-detrital primary zircon data to investigate the efficacy of grain shape analysis to better resolve the basin’s mineral provenance. Zircon Hf isotope compositions indicate a primary Mesoproterozoic juvenile source for zircon melts (∼1250–1000 Ma, −2.5 < ɛHf > ∼+5) with additional contributions from a range of juvenile to evolved late Archean to Phanerozoic-aged zircon bearing magmas (−28.0 < ɛHf > +11). U–Pb geochronology and Hf isotopes are incapable of differentiating Mesoproterozoic-aged source rocks bounding the region for the majority of heavy mineral deposits analyzed as potential sources express overlapping crystallization ages and similarities in Hf-isotope characteristics. However, distinct zircon grain shapes (i.e., perimeter, major axis and circularity) facilitate improved differentiation across these Mesoproterozoic sources. Filtering of U–Pb age, Hf isotope and shape data implicate the underlying Madura and Coompana provinces as dominant sediment sources for Eucla Basin detritus aged ∼1400–1000 Ma. The lack of direct sediment pathways between the underlying basement provinces and placer sediments analyzed demonstrates the significance of zircon reworking from intermediate sedimentary basins in the formation of the economically significant Eucla Basin beach placers. Zircon grain shape represents a cheaply acquired and readily incorporated grain characteristic that can enhance provenance investigations.

Abstract Image

单一尺寸并不适用于所有尺寸:通过综合粒度、地质年代和Hf同位素分析来完善锆石物源解释
沉积物物源研究通常利用同位素特征来确定碎屑矿物的来源和路线。然而,在地理上不同的晶体源区,非独特的年龄和地球化学特征可能导致矿物物源解释的显著模糊性。这种模糊性在拥有世界级重矿砂资源的澳大利亚南部新生代尤克拉盆地中表现得很明显。本文提供了4个重矿物远景区(N = 8, N = 844 [N =样品,N =颗粒])新的Hf同位素数据。本文还介绍了一套尤克拉盆地(N = 22, N = 35604)和盆地下伏基底(N = 13, N = 824)的锆石颗粒形状数据。将这些数据与已公布的碎屑和非碎屑原生锆石数据相结合,探讨颗粒形状分析对更好地解决盆地矿物物源问题的有效性。锆石Hf同位素组成表明,锆石熔体的原始中元古代幼年源(~ 1250-1000 Ma,−2.5 <ɛ高频祝辞~ +5),从幼年期到演化的晚太古宙到显生宙的含锆石岩浆(−28.0 <ɛ高频祝辞+ 11)。U-Pb年代学和Hf同位素不能区分与该地区交界的中元古代烃源岩,分析的大多数重矿床的潜在烃源岩表现出重叠的结晶年龄和Hf同位素特征的相似性。然而,不同的锆石颗粒形状(即周长、长轴和圆形)促进了这些中元古代源区之间的分化。U-Pb年龄、Hf同位素和形状数据的过滤表明,下伏的Madura和compana省是尤克拉盆地碎屑的主要沉积物来源,年龄为~ 1400-1000 Ma。下伏基底省与砂质沉积物之间缺乏直接的沉积路径,说明中间沉积盆地的锆石改造对形成具有重要经济意义的尤克拉盆地滩砂具有重要意义。锆石颗粒形状代表了一种廉价且易于合并的颗粒特征,可以加强物源研究。
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来源期刊
Geoscience frontiers
Geoscience frontiers Earth and Planetary Sciences-General Earth and Planetary Sciences
CiteScore
17.80
自引率
3.40%
发文量
147
审稿时长
35 days
期刊介绍: Geoscience Frontiers (GSF) is the Journal of China University of Geosciences (Beijing) and Peking University. It publishes peer-reviewed research articles and reviews in interdisciplinary fields of Earth and Planetary Sciences. GSF covers various research areas including petrology and geochemistry, lithospheric architecture and mantle dynamics, global tectonics, economic geology and fuel exploration, geophysics, stratigraphy and paleontology, environmental and engineering geology, astrogeology, and the nexus of resources-energy-emissions-climate under Sustainable Development Goals. The journal aims to bridge innovative, provocative, and challenging concepts and models in these fields, providing insights on correlations and evolution.
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