The social share element is found in article.html

.footer-social {
   padding: 0;
   margin-top: 10px;
   list-style-type: none;
   &__item {
    margin: 5px 3px;
    display:inline-block;
    position: relative;
    a {
    padding: 22px;
    text-align:center;
    display: block;
    color: #666;
    }
    a:hover {
    color: #666;
    }
  }
}

The icons are created with fontawesome

The style can be modified on app/css/scss/_site-footer.scss