Of course you can, just need an extra div!
<div class="fixed-wrapper">
<div class="close-wrapper">
<div class="close"></div>
</div>
</div>
body
background: gray
height: 8000px
.fixed-wrapper
position: fixed
top: 20px
left: 0
right: 0
.close-wrapper
max-width: 1200px
position: relative
.close
background: #fff
width: 30px
height: 30px
position: absolute
right: 0
border: 1px solid #515151
&:before,&:after
width: 25px
height: 1px
background: #515151
content: ''
position: absolute
top: 50%
left: 50%
display: block
@include transform(translate(-50%, -50%) rotate(45deg))
&:after
transform: translate(-50%, -50%) rotate(-45deg)
See this fiddle I made for you :-)
http://codepen.io/marinagallardo/pen/mJyqaN