Hello Stylianos and sorry for the delay,
here are my details :
a: EAR/lib contains :
EAR/lib/log4j-1.2.16.jar
---/slf4j-api-1.5.8.jar
---/slf4j-log4j12-1.5.8.jar
b: the file jboss-deployment-structure.xml ->
=======================================
<?xml version="1.0" encoding="UTF-8"?>
<jboss-deployment-structure xmlns="urn:jboss:deployment-structure:1.0" >
<ear-subdeployments-isolated>false</ear-subdeployments-isolated>
<deployment>
<exclusions>
<module name="org.apache.log4j"/>
<module name="org.slf4j"/>
<module name="org.slf4j.impl"/>
</exclusions>
</deployment>
<sub-deployment name="<frontend>.war">
<exclusions>
<module name="org.apache.log4j"/>
<module name="org.slf4j"/>
<module name="org.slf4j.impl"/>
</exclusions>
</sub-deployment>
<sub-deployment name="<backend>.jar">
<exclusions>
<module name="org.apache.log4j"/>
<module name="org.slf4j"/>
<module name="org.slf4j.impl"/>
</exclusions>
</sub-deployment>
</jboss-deployment-structure>
==========================
c: only jboss-deployment-structure.xml exists on EAR/META-INF
but the file log4j.xml resides in the <backend>.jar/log4j.xml
d: MANIFEST.MF is empty (created by maven)