nginx serve static files over both https and http - http

Question

So, I want to secure only the login and admin part of my website. The problem is that the admin uses some common static files that are used on the general site as well. This means that when I am in the admin those files should be served over https while when I am on the general site they should be served as http.
How can I configure nginx to behave this way?
The configuration I use so far is bellow:
server {
listen 80;
server_name site.com www.site.com;
root /home/site_folder/web;
index index.php;
location ~ /(get-involved|contribute|api) {
return 301 https://$server_name$request_uri;
}
location ~ \.php$ {
include /etc/nginx/fastcgi_params;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_param HTTPS on;
fastcgi_param SCRIPT_FILENAME /home/site_folder/web/index.php;
}
location / {
root /home/site_folder/web;
if (-f $request_filename) {
expires max;
break;
}
try_files $uri $uri/index.php;
rewrite ^(.*) /index.php last;
}
}
server {
listen 443 ssl;
ssl_certificate path_to_ssl.crt;
ssl_certificate_key path_to_key.key;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers HIGH:!aNULL:!MD5;
server_name site.com www.site.com;
root /home/site_folder/web;
index index.php;
location ~ /(get-involved|contribute|api) {
root /home/site_folder/web;
if (-f $request_filename) {
expires max;
break;
}
try_files $uri $uri/index.php;
rewrite ^(.*) /index.php last;
}
location ~ \.php$ {
include /etc/nginx/fastcgi_params;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
fastcgi_param HTTPS on;
fastcgi_param SCRIPT_FILENAME /home/site_folder/web/index.php;
}
location / {
return 301 http://$server_name$request_uri;
}
}