We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick disk component .
A sample of 176 nearby ( d \leq 150 pc ) thick disk candidate stars was chosen from the Hipparcos catalogue and subjected to a high-resolution spectroscopic analysis .
Using accurate radial velocities combined with Hipparcos astrometry , kinematics ( U,V, and ~ { } W ) and Galactic orbital parameters were computed .
We estimate the probability for a star to belong to the thin disk , the thick disk or the halo .
With a probability P \geq 70 % taken as certain membership , we assigned 95 stars to the thick disk , 13 to the thin disk , and 20 to the halo .
The remaining 48 stars in the sample can not be assigned with reasonable certainty to one of the three components .

Abundances of C , O , Na , Mg , Al , Si , Ca , Sc , Ti , V , Cr , Mn , Fe , Co , Ni , Cu , Zn , Y , Ba , Ce , Nd , and Eu have been obtained .
The abundances for thick disk stars are compared with those for thin disk members from Reddy et al .
( 2003 ) .
The ratios of \alpha -elements ( O , Mg , Si , Ca and Ti ) to iron for thick disk disk stars show a clear enhancement compared to thin disk members in the range -0.3 < [ Fe/H ] < -1.2 .
There are also other elements – Al , Sc , V , Co , and possibly Zn – which show enhanced ratios to iron in the thick disk relative to the thin disk .
The abundances of Na , Cr , Mn , Ni , and Cu ( relative to Fe ) are very similar for thin and thick disk stars .
The dispersion in abundance ratios [ X/Fe ] at given [ Fe/H ] for thick disk stars is consistent with the expected scatter due to measurement errors , suggesting a lack of ‘ cosmic ’ scatter .

A few stars classified as members of the thick disk by our kinematic criteria show thin disk abundances .
These stars , which appear older than most thin disk stars , are also , on average , younger than the thick disk population .
They may have originated early in the thin disk history , and been subsequently scattered to hotter orbits by collisions .
The thick disk may not include stars with [ Fe/H ] > -0.3 .
The observed compositions of the thin and thick disks seem to be consistent with models of galaxy formation by hierarchical clustering in a \Lambda CDM universe .
In particular , the distinct abundance patterns observed in the thin and thick disks , and the chemical homogeneity of the thick disk at different galactocentric distances favor a scenario in which the majority of thick-disk stars were formed in situ , from gas rich merging blocks .