Dear Sidney:

Local marriage customs are not generally the concern of the Church. The marriage must be a Catholic wedding according to the rules for canonical form for Catholic weddings; it cannot be a "mixed" wedding ceremony (i.e. Catholic/Hindu).

But, local customs as to things like dress, rings, reception traditions, etc. are not the concern of the Church, at least unless such customs relate to false gods and the like.

The Mangalsutra, as a symbol of marriage, as I understand it, is no different that the Western tradition of the wedding ring. As a symbol of marriage I do not see a problem.

To get a definitive answer I would contact the local diocese in India as ask about it, but as far as I know there is no inherent problems with such local customs.

I am a little surprised by the Biblical question.  First of all, this question applies to customs not doctrine, and thus this is not a matter of Biblical support to begin with. Most of the traditional marriage customs of the West are never mentioned in the Bible.

Secondly, as any Catholic knows, the Bible does not contain all of God's Revelation. The Bible itself says that not all the teachings of Christ are in the Bible.

Thus, whether or not there are specific Bible references to support a doctrinal position is not important. What is important is that doctrinal positions be supported by God's Revelation, the Bible, as Sacred Written Tradition, of which is only one part, or the other part of Revelation, which is Sacred Oral Tradition. All of God's Revelation, Written and Oral, is protected by and definitively taught by the Magisterium of the Catholic Church.

But, this matter of what you ask is not doctrinal, it is about local customs.

God Bless,
Bro. Ignatius Mary