  We present results derived from VLT-FORS2 spectra of 24 different globular
clusters associated with the lenticular galaxy NGC3115. A subsample of 17
globular clusters have sufficiently high signal-to-noise to allow precision
measurements of absorption line-strengths. Comparing these indices to new
stellar population models by Thomas et al. we determine ages, metallicities and
element abundance ratios. Our data are also compared with the Lick/IDS
observations of Milky Way and M31 globular clusters. Unpublished higher order
Balmer lines (HgammaA,F and HdeltaA,F) from the Lick/IDS observations are given
in the Appendix. Our best age estimates show that the observed clusters which
sample the bimodal colour distribution of NGC3115 are coeval within our
observational errors (2-3 Gyr). Our best calibrated age/metallicity diagnostic
diagram (Hbeta vs [MgFe]) indicates an absolute age of 11-12 Gyr. We confirm
with our accurate line-strength measurements that the (V-I) colour is a good
metallicity indicator within the probed metallicity range. The abundance ratios
for globular clusters in NGC3115 give an inhomogeneous picture. We find a range
from solar to super-solar ratios for both blue and red clusters. From our
accurate recession velocities we detect, independent of metallicity, clear
rotation in the sample of globular clusters. In order to explain the
metallicity and abundance ratio pattern, particularly the range in abundance
ratios for the metal rich globular clusters in NGC3115, we favour a formation
picture with more than two distinct formation episodes.(Abridged)
