The provenance of late Cenozoic East Asian Red Clay: Tectonic-metamorphic history of potential source regions and a novel combined zircon-rutile approach

Katja Bohm,Thomas Stevens,Anu Kaakinen,Yann Lahaye,Hugh O'Brien,Zhaoqun Zhang

doi:10.1016/j.earscirev.2021.103909

Abstract

Constraining the provenance of aeolian mineral dust is critical in understanding past climate changes, atmospheric dust activity, circulation, and sediment generation. On the Chinese Loess Plateau (CLP), use of detrital zircon U-Pb age data as source tracers for the dust has seen a huge growth and lead to breakthroughs in understanding dust provenance. However, significant ambiguities remain especially regarding the provenance of the aeolian Neogene Red Clay (RC). To address this, here we review the state of the art of understanding of Neogene RC provenance, with a focus on single-grain analyses, and introduce detrital rutile geochemistry as a tool to complement zircon U-Pb dating. Furthermore, to better utilise the link between the detrital minerals and their primary origin, we compile primary source region geologic background and single-grain data relevant for use of geochronological and metamorphic provenance proxy minerals. We discuss four major tectonic divisions in northern China and southern Mongolia: North China Craton (NCC), Tarim Craton (TC), Central China Orogen (CCO), parts of the Central Asian Orogenic Belt (CAOB), and briefly summarize the Tibetan-Himalayan orogen. Many of these regions have been tectonically active during the same time periods in the Earth's history, and our analysis demonstrates how use of zircon age data alone has limitations in differentiating between a number of key potential dust sources to the CLP. Addition of a metamorphic source tracer such as rutile allows some of these possible source areas to be distinguished. For example, the proximal northern NCC regions that show high−/ultrahigh-temperature metamorphic conditions can potentially be diagnostic of a northerly source component to CLP dust. Our combined zircon-rutile data analysis of ca. 4 Ma Nihewan RC in northern CLP verifies the utility of the novel rutile provenance proxy in sourcing CLP sediments. The zircon and rutile data suggest similar dust provenance: the dominant sources are proximal areas on the NCC, while contributions from the dry areas in parts of the CAOB, central deserts, and the Yellow River are also likely. Our results also hint at a minor source component deriving from distal western source regions in the TC, and/or in the central parts of the CCO, but rutile data from potential secondary source areas are needed to verify this possibility. We also conclude that multi-proxy single-grain provenance analyses are needed for more reliable provenance analyses.

Highlights

The information linking an eroding original rock and a subsequent sediment deposit can persist in a detrital mineral grain for millions of years
In this paper, we address these gaps by 1) synthesizing understanding of the geologic background of potential primary source areas of the late Neogene Chinese Loess Plateau (CLP) dust, which enables clear identification of key features that both facilitate and complicate single-grain provenance interpretations; 2) compiling existing single-grain provenance datasets as well as; 3) reviewing past Neogene dust provenance work on the CLP in order to reveal the current understanding from existing studies; and 4) testing a new combined single-grain zircon age and rutile geochemistry provenance approach that aims to utilise both crustal formation age and metamorphism information to assign dust sources and thereby greatly refine future provenance interpretations of dust to the CLP
While some of the geological history of the Central China Orogen (CCO) is complex and extends back to Archean, most of the CCO formed during Neoproterozoic and early Palaeozoic

Summary

Introduction

The information linking an eroding original (primary) rock and a subsequent sediment deposit can persist in a detrital mineral grain for millions of years. This fundamental information has been out of reach for fine-grained, dominantly silt to clay sized wind-blown sediments (deposits of atmospheric mineral dust), but recently has become more attainable because new analytical instruments are capable of singlegrain analyses of fine silt particles This is of crucial importance as it is increasingly recognised that atmospheric mineral dust plays a signif icant role in the global climate system, yet this role is still poorly un derstood, and the multiple interactions between dust and climate are hard to fully synthesize in climate models (Kohfeld and Harrison, 2001; Shao et al, 2011; Tegen, 2003). Dust acts as an agent of climate change, but

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