Detrital zircon record of Cambrian (meta‐)sedimentary strata in the western part of the Baoshan Block: Constraints on its eastern boundary and Early Palaeozoic palaeoposition
5
Citation
80
Reference
10
Related Paper
Citation Trend
Abstract:
The premise to discuss the evolution of an orogenic belt is to understand the origins and tectonic affinities of various blocks that constitute the orogen. The Baoshan Block in the SE Tibetan Plateau is an ultimate window to observe the orogenic evolution, but its origin and eastern boundary remains debated. In this contribution, we report new detrital zircon U–Pb ages and Hf isotopic data from the Cambrian Baoshan Formation in the middle–western part of the Baoshan Block. Detrital zircon ages range from the Archean to Early Palaeozoic, with age peaks at ~2.5, ~0.95, and ~0.55 Ga. Zircon ε Hf (t) values exhibit a wide range from negative to positive for each of the three major age groups, indicating diverse magma sources. The eastern boundary for the Baoshan Block should be extended from the Kejie‐Nandinghe Fault to the Changning‐Menglian suture belt, based on not only comparisons of Early Palaeozoic magmatism, sedimentary facies, and provenances for the Palaeozoic strata that developed on both sides of the Kejie‐Nandinghe Fault but also on the regional tectonic framework correlation. The Baoshan Block should be along the Indian margin as the Qiangtang, Tengchong, and Simao‐Indochina blocks in Early Palaeozoic according to the provenance analyses.Cite
Cite
Citations (5)
Cite
Citations (8)
Abstract Single grain zircon U-Pb geochronology has demonstrated great potentials in extracting tectonic and atmospheric circulation signal carried by aeolian, fluvial, and fluviolacustrine sediments. A routine in this sort of studies is analyzing 100–150 grains and then compares zircon U-Pb age spectra between the measured sample and the potential sources. Here we compared the zircon U-Pb age results of the late Miocene-Pliocene Red Clay sequence of two neighboring sites from the Chinese Loess Plateau where similar provenance signal is expected. Although the results from the 5.5 Ma sediment support this prediction, the results from the 3 Ma sediment at these two sites differ from each other significantly. These results emphasize the importance of increasing analysis number per sample and combining the zircon U-Pb geochronology with other provenance tools in order to get reliable provenance information.
Geochronology
Loess plateau
Cite
Citations (9)
Devonian
Cite
Citations (0)
The Neoproterozoic to Devonian sedimentary successions of Severnaya Zemlya, in the Russian high Arctic, have been sampled for detrital zircon provenance studies. 50-100 zircons were analyzed from 1 ...
Baltica
Cite
Citations (62)
Abstract Detrital zircon U-Pb studies of mudstone provenance are rare but may preferentially fingerprint distal zircon sources. To examine this issue, Pierre Shale and Trinidad Sandstone deposited in a Late Cretaceous deltaic environment in the Raton Basin, Colorado (USA), were measured for detrital zircon U-Pb age by laser ablation–inductively coupled plasma–mass spectrometry. Two major detrital zircon age peaks at ca. 70 and 1690 Ma are found in both Pierre Shale and Trinidad Sandstone but in inversely varying proportions: 68% and 16%, respectively, for the finest zircon fraction (~15–35 μm) in the shale, and 25% and 32%, respectively, for the coarsest zircon fraction (~60–80 μm) in the sandstone. Proximal sources in the Sangre de Cristo Mountains, directly west of the Raton Basin, contain coarse-grained, ca. 1690 Ma zircon, whereas distal sources in Laramide uplifts and basins in Colorado, New Mexico, and Arizona contain fine-grained, ca. 70 Ma zircon. The results indicate that U-Pb zircon provenance of mudstone reflects availability of volcanic and other fine-grained source rocks rather than simply distal sources. U-Pb zircon provenance studies should routinely include mudstone units because these units may identify fine-grained zircon sources more reliably than sandstones alone.
Geochronology
Cite
Citations (8)
Detrital zircon U-Pb and muscovite 40Ar/39Ar dating are useful tools for investigating sediment provenance and regional tectonic histories. However, the two types of data from same sample do not necessarily give consistent results. Here, we compare published detrital muscovite 40Ar/39Ar and zircon U-Pb ages of modern sands from the Yangtze River to reveal potential factors controlling differences in their provenance age signals. Detrital muscovite 40Ar/39Ar ages of the major tributaries and main trunk suggest that the Dadu River is a dominant sediment contributor to the lower Yangtze. However, detrital zircon data suggest that the Yalong, Dadu, and Min rivers are the most important sediment suppliers. This difference could be caused by combined effects of lower reaches dilution, laser spot location on zircons and difference in closure temperature and durability between muscovite and zircon. The bias caused by sediment laser spot targeting a core or rim of zircon and zircon reworking should be considered in provenance studies.
Muscovite
Thermochronology
Cite
Citations (35)
ABSTRACT Detrital-zircon records of provenance are used to reconstruct paleogeography, sediment sources, and tectonic configuration. Recognition of biases in detrital-zircon records that result from grain-size-dependent processes adds new complexity and caution to the interpretation of these records. We begin by investigating possible size-dependent biases that may affect interpretation of detrital-zircon provenance records in an idealized sedimentary system. Our modeling results show that settling and selective entrainment can differentially affect detrital-zircon spectra if an initial size variation between source zircon populations exists. We then consider a case study: a detrital-zircon record from Ediacaran to Terreneuvian strata of Death Valley, USA, with a focus on the Rainstorm Member of the Johnnie Formation. The detrital-zircon record of the Rainstorm Member shows that despite its unusual, heavy-mineral-rich character, the provenance of the unit is like other units in the succession. Size and density measurements of the grains of the deposit suggest that its enriched heavy-mineral suite is best explained through concentration by selective entrainment and winnowing. The relationship between detrital-zircon grain size and age for samples from the Johnnie Formation are consistent with grain-size influence on the interpretation of provenance, especially for large Grenville-age (1.0–1.2 Ga) zircons. Grain size can exert significant bias on a provenance interpretation and must be accounted for in provenance studies.
Heavy mineral
Geologic record
Cite
Citations (17)