  Let $d \geq 2$ and $n\geq 3$ be two natural numbers. Given any sequence
$\kappa=(k_1,\dots,k_n) \in \mathbb{Z}^n$ such that $\gcd(k_1,\dots,k_n,d)=1$,
we consider the family of Riemann surfaces obtained from the plane curves
defined by $y^d=\prod_{i=1}^n(x-b_i)^{k_i}$, where $\{b_1,\dots,b_n\}$ are $n$
distinct points in $\mathbb{C}$. The monodromy of the cohomology of the fibers
of this family provides us with a representation of the pure braid group
$\mathrm{PB}_n$ into some symplectic group. By restricting to a specific
subspace in the cohomology of the fibers, we obtain a representation $\rho_d$
of $\mathrm{PB}_n$ into a linear algebraic group defined over $\mathbb{Q}$. In
a sense, $\rho_d$ is primitive with respect to the parameters $d$ and $\kappa$.
The first main result of this paper is a criterion for the Zariski closure of
the image of $\rho_d$ to be maximal, and the second main result is a criterion
for the image to be an arithmetic lattice in the target group. The latter
generalizes previous results of Venkataramana and gives an answer to a question
by McMullen.
