Branched arrows with different thickness

Question

I am trying to create an arrow, looking like this:

Is it possible?

Answer 1

Here is a proposal in which I recycle the outlined arrow from this answer. Wiping out the unwanted boundary is possible, but the most straightforward way I see uses calc and goes in three steps.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,decorations.text,decorations.markings,calc} %  decorations.text just 4 fun
\pgfkeys{/tikz/.cd,
    outlined arrow width/.store in=\OutlinedArrowWidth,
    outlined arrow width=10pt,
    outlined arrow step/.store in=\OutlinedArrowStep,
    outlined arrow step=1pt,
    outlined arrow length/.store in=\OutlinedArrowLength,
    outlined arrow length=5pt,
}

\pgfdeclaredecoration{outlined arrow}{initial}
{% initial arrow butt
\state{initial}[width=\OutlinedArrowStep,next state=cont] {
    \pgfmoveto{\pgfpoint{\OutlinedArrowStep}{\OutlinedArrowWidth/2}}
    \pgfpathlineto{\pgfpoint{0.3\pgflinewidth}{\OutlinedArrowWidth/2}}
    \pgfpathlineto{\pgfpoint{0.3\pgflinewidth}{-\OutlinedArrowWidth/2}}
    \pgfpathlineto{\pgfpoint{1pt}{-\OutlinedArrowWidth/2}}
    \pgfcoordinate{lastup}{\pgfpoint{1pt}{\OutlinedArrowWidth/2}}
    \pgfcoordinate{lastdown}{\pgfpoint{1pt}{-\OutlinedArrowWidth/2}}
    \xdef\marmotarrowstart{0}
  }
  \state{cont}[width=\OutlinedArrowStep]{
    \ifdim\pgfdecoratedremainingdistance>\OutlinedArrowLength% continue the outlined path
     \pgfmoveto{\pgfpointanchor{lastup}{center}}
     \pgfpathlineto{\pgfpoint{\OutlinedArrowStep}{\OutlinedArrowWidth/2}}
     \pgfcoordinate{lastup}{\pgfpoint{\OutlinedArrowStep}{\OutlinedArrowWidth/2}}
     \pgfmoveto{\pgfpointanchor{lastdown}{center}}
     \pgfpathlineto{\pgfpoint{\OutlinedArrowStep}{-\OutlinedArrowWidth/2}}
     \pgfcoordinate{lastdown}{\pgfpoint{\OutlinedArrowStep}{-\OutlinedArrowWidth/2}}
    \else
     \ifnum\marmotarrowstart=0% draw the arrow head
     \pgfmoveto{\pgfpointadd{\pgfpointanchor{lastup}{center}}{\pgfpoint{-0.5\pgflinewidth}{0}}}
     \pgflineto{\pgfpoint{-0.5\pgflinewidth}{\OutlinedArrowWidth}}
     \pgflineto{\pgfpointadd{\pgfpointdecoratedpathlast}{\pgfpoint{-0.5\pgflinewidth}{0}}}
     \pgflineto{\pgfpoint{-0.5\pgflinewidth}{-\OutlinedArrowWidth}}
     \pgflineto{\pgfpointadd{\pgfpointanchor{lastdown}{center}}{\pgfpoint{-0.5\pgflinewidth}{0}}}
     \xdef\marmotarrowstart{1}
     \else
     \fi
    \fi%
  }
  \state{final}[width=5pt]
  { % perhaps unnecessary but doesn't hurt either
    \pgfmoveto{\pgfpointdecoratedpathlast}
  }
}
\begin{document}


\begin{tikzpicture}[decoration=outlined arrow,font=\sffamily]
 \node[draw,minimum width=3cm,minimum height=4cm] (A) at (0,0) {};
 \node[draw,minimum size=1cm,anchor=west] (B) at (5,2.5) {};
 \node[draw,minimum size=1.2cm,anchor=west] (C) at (5,-1.5) {};
 \draw[decorate,outlined arrow length=15pt,outlined arrow width=20pt,
 postaction={decorate,decoration={markings,
 mark=at position 0.3 with {\path (0,0pt) coordinate (X1);},
 mark=at position 0.35 with {\path (0,5pt) coordinate (X3);},
 mark=at position 0.4 with {\path (0,0pt) coordinate (X2);}}}] (A.east)
 to[out=0,in=-180] (C.west);
 \draw[decorate,postaction={decorate,decoration={markings,
 mark=at position 0 with {\path (0,0pt) coordinate (Y1)  (0,10pt) coordinate (Y2);}
 }}] (X3) to[out=50,in=-180] (B.west);
 \path (X1) -- (Y1) coordinate[pos=-0.05] (aux1)  coordinate[pos=1.05] (aux2);
 \path (Y2) -- (X2) coordinate[pos=-0.05] (aux3)  coordinate[pos=1.05] (aux4);
 \fill[white] (aux1) -- (aux2)-- (aux3) -- (aux4) -- cycle;
 \draw  let \p1=($(X2)-(X1)$),\n1={atan2(\y1,\x1)} in (X1) to[out=\n1,in=-130] (Y1);
 \draw let \p1=($(X2)-(X1)$),\n1={atan2(\y1,\x1)-180} in (X2) to[out=\n1,in=-130] (Y2);
\end{tikzpicture}  
\end{document}