\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[ngerman,greek,english]{babel}



\usepackage{float}








\begin{document}

\title{The Carbonate Veins Documenting the Tectonic Evolution of the South
China Sea Continental Margin from Early Cretaceous to Early Cenozoic}



\author[1]{Liheng Sun}%
\author[2]{Zhen Sun}%
\author[3]{Yunying Zhang}%
\author[4]{Zhongxian Zhao}%
\author[5]{Jianxin Zhao}%
\author[2]{Zhang Zhe}%
\author[6]{Longtao Sun}%
\author[7]{Xiaoxi Zhu}%
\affil[1]{SCSIO South China Sea Institute of Oceanology}%
\affil[2]{South China Sea Institute of Oceanology, Chinese Academy of Sciences}%
\affil[3]{The University of Hong Kong}%
\affil[4]{SCSIO South China Sea Institute of Oceanology, Chinese Acaademy of Sciences}%
\affil[5]{University of Queensland}%
\affil[6]{SCSIO South China Sea Institute of Oceanology, Chinese Academy of Sciences}%
\affil[7]{Hohai University}%


\vspace{-1em}



  
  \date{May 24, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
The transition from active to passive continental margin of the South
China Sea (SCS) is usually inferred to occur in the Late Mesozoic to
Early Cenozoic. However, it is less known about the tectonic
characteristics of active continental margins before the Late Mesozoic,
which hampers the recognition of integral evolution of the SCS. The
International Ocean Discovery Program (IODP) site U1504 has sampled
greenschist facies mylonite from the basement in the Outer Margin High
of the northern SCS continental margin, which potentially record the
Mesozoic and Cenozoic tectonic evolution of the SCS region. The
microstructure has identified two episodes of deformation in the
mylonite, namely early ductile and late brittle deformation, but without
age constraints. Here, we further identify three episodes of carbonate
veins (pre-mylonite, syn-mylonite and post-mylonite) in the greenschist
facies mylonite according to the intersecting relationship between the
veins and the mylonite foliation. Then we select 10 carbonate samples
for in situ U-Pb dating, and obtain three accurate ages. The
pre-mylonite carbonate veins are dated to 210 \selectlanguage{ngerman}± 20 Ma and 195 ± 32 Ma,
respectively, which might denote the age of the protolith clast. The age
of the syn-mylonite carbonate vein is 135 ± 12 Ma. But for the
post-mylonite carbonate veins, no effective age was obtained using U-Pb
dating method. Post-mylonite carbonate veins and late brittle fractures
were formed at the same time, and the formation environment is similar
to the overlying Late Eocene bioclastic limestone. Therefore, combining
the microstructure, geochemistry and seismic profile, we speculate that
the post-mylonite carbonate veins and brittle fractures may be formed
during the Early Cenozoic rifting. These dating ages of the three
episodes of carbonate veins suggest that the mylonite records at least
two main periods of continental extension in the SCS region since the
Early Cretaceous. In reference to the Mesozoic tectonic settings, we
infer that, due to the slab rollback of the subducting paleo-Pacific,
the SCS continental margin started significant extension during the
Early Cretaceous as shown by the ductile deformation of the mylonite. In
the Early Cenozoic, the mylonite was exhumated to the seafloor along
with further continental extension, and weak brittle deformation
occurred in the mylonite. Therefore, the Early Cretaceous extension of
the SCS active continental margin may have a certain promotion effect on
the rupture of the passive continental margin in the Cenozoic. Keywords:
Greenschist facies mylonite; Carbonate U-Pb dating; Continental margin
of the SCS; Early Cretaceous; IODP 368%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Multi-stage carbonate veins at IODP Site U1504 document Early
Cretaceous to early Cenozoic extensional events on the South China Sea
margin}

Liheng Sun\textsuperscript{a, b}, Zhen Sun\textsuperscript{a, b, c,} *,
Yunying Zhang\textsuperscript{a}, Zhongxian Zhao\textsuperscript{a, *},
Jianxin Zhao\textsuperscript{d}, Cuimei Zhang\textsuperscript{a}, Zhe
Zhang\textsuperscript{a, b}, Longtao Sun\textsuperscript{a}, Xiaoxi
Zhu\textsuperscript{a, b}

\textsuperscript{a} \emph{Southern Marine Science and Engineering
Guangdong Laboratory (Guangzhou), Key Laboratory of Ocean and Marginal
Sea Geology, South China Sea Institute of Oceanology, Innovation Academy
of South China Sea Ecology and Environmental Engineering, Chinese
Academy of Sciences, Guangzhou 511458, China}

\textsuperscript{b} \emph{University of Chinese Academy of Sciences,
Beijing 100049, China}

\textsuperscript{c} \emph{China-Pakistan Joint Research Center on Earth
Sciences, CAS-HEC, Islamabad 45320, Pakistan}

\textsuperscript{d} \emph{Radiogenic Isotope Facility, School of Earth
and Environmental Sciences, The University of Queensland, Brisbane, QLD
4072, Australia}

\emph{* Corresponding Author:}

\emph{Z. Sun, Email address:zhensun@scsio.ac.cn} \textbf{;}\emph{Z.
Zhao, Email address:zxzhao@scsio.ac.cn}

\textbf{Abstract}

Recognition of the pre-spreading tectonic characteristics of the South
China Sea (SCS) continental margin is key to understanding how the SCS
opened. However, information on this subject is extremely scarce because
of the lack of direct chronological constraints on deformation events.
The International Ocean Discovery Program sampled greenschist-facies
mylonite from the basement of the Outer Margin High at site U1504 in the
SCS, which could provide information on the pre-spreading history. The
microstructure analysis revealed that two episodes of extension had
affected the mylonites, namely early ductile and late brittle
deformation. Pre-mylonite, syn-mylonite and post-mylonite carbonate
veins were identified on the basis of the intersecting relationships
with the mylonite foliation. The pre-mylonite carbonate veins yielded
U--Pb ages of 210 \selectlanguage{ngerman}± 20 and 195 ± 32 Ma, which might represent the age of
the protolith. The age of the syn-mylonite carbonate vein is 135 ± 12
Ma. No effective ages were obtained for the post-mylonite carbonate
veins using U--Pb dating. The \selectlanguage{greek}δ\selectlanguage{english}\textsuperscript{13}C,
\selectlanguage{greek}δ\selectlanguage{english}\textsuperscript{18}O and\textsuperscript{87}Sr/\textsuperscript{86}Sr
compositions of the post-mylonite carbonate veins suggest that they were
formed by hydrothermal fluid precipitation dominated by seawater.
Considering the extensively developed marine environment in the northern
continental margin after the late Eocene, the post-mylonite carbonate
veins at site U1504 likely formed in the Eocene or later. Combining the
microstructure, geochemistry and seismic profile, we hypothesize that
post-mylonite carbonate veins were formed during early Cenozoic rifting.
In reference to the geological background, we conclude that the basement
of the SCS margin experienced at least two stages of extension before
spreading: the first stage occurred during the Early Cretaceous and was
caused by rollback of the Paleo-Pacific plate; the second occurred in
the early Cenozoic because of passive rifting. These multiple
extensional events of the active continental margin and of the passive
margin collectively resulted in thinning the SCS continental margin.

\textbf{Keywords:} Continental margin of the South China Sea;
Pre-spreading tectonics; International Ocean Discovery Program 368;
Greenschist-facies mylonite; Carbonate U--Pb dating

\selectlanguage{english}
\FloatBarrier
\end{document}

