I have some good news for you. There are a few DECs still living in MAZURY village.
Adam Dec, Mazury, TEL 17 2285523
Andrzej Dec, Mazury, TEL 17 2280292
Dariusz Dec, Mazury, TEL 17 2280057
Marcin Dec, Mazury, TEL 17 2280201
Stanis?aw Dec, Mazury,TEL 17 2285465
Tadeusz Dec, Mazury, TEL 17 2280031
Writing them a letter may give you some results.
I have also found, on the Internet, MARCIN DEC, a teacher, whose grandfather was born at Mazury. Based on a query, carried out by late dr. KAZIMIERZ SKOWRO?SKI (very well known historian and colonization’s researcher of PUSZCZA SANDOMIERSKASANDOMIERZ WILDERNESS) he claims, amongst others, that the Dec surname (German origin of DIETZ) emerged in this area already in the second half of the 16th century (1569) Here is his email address: (hopefully still actual) email@example.com
Just for my own curiosity- Do you know what language did your ancestors speak, and what was their religion?